Abstract Book

November 4-5, 2019

Duisburg, Germany

Joint Symposium

"Nanomaterials for Energy Applications"

TABLE OF CONTENT 1

Agenda 3

Talks 7

Posters 49

AGENDA 3

November 4, 2019 (Monday)

09:30 Registration

10:15 Malte Behrens (Deputy Scientific Director CENIDE,

Speaker CRC/TRR 247, UDE)

Takaki Kanbara (Director TREMS, Tsukuba)

Tobias Teckentrup (Managing Director CENIDE, UDE)

Opening Remarks

Chairman: Malte Behrens (CENIDE, UDE)

10:30 – 11:00 Takaki Kanbara (TREMS, Tsukuba)

Direct arylation polycondensation: Facile access to semiconducting

polymers

11:00- 11:30 Yohei Yamamoto (TREMS, Tsukuba)

Self-Assembled Organic Semiconductor Microlasers and Microarrays

11:30 – 12:00 Tilmar Kümmell (CENIDE, UDE)

Scalable optoelectronic devices based on 2D semiconductors

12:00 – 12:15 Group photo

12:15 – 13:30 Lunch and poster session

13:30 – 14:30 Lab tour NanoEnergieTechnikZentrum (NETZ) and

Interdisciplinary Center for Analytics on the Nanoscale (ICAN)

Chairman: Takaki Kanbara (TREMS, Tsukuba)

14:30 – 15:00 Nicolas Wöhrl (CENIDE, UDE)

Single-source, One-step Plasma Synthesis of Carbon Nanowall Hybrid

Materials

15:00 – 15:30 Oleg Prymak (UDE)

Temperature-induced transformation in CuO/MgO and CuO/ZnO pre-

catalysts studied by in situ XRD and TEM

15:30 – 16:00 Coffee Break

AGENDA 4

Chairman: Yohei Yamamoto (TREMS, Tsukuba)

16:00 – 16:30 Niels Benson (CENIDE, UDE)

Trap Evaluation in MAPI thin films for photovoltaic applications

16:30 – 17:00 Yutaka Moritomo (TREMS, Tsukuba)

Tertiary battery as energy-harvesting device

17:00 – 17:30 Roland Schmechel (CENIDE, UDE)

Thermoelectrics with bipolar charge carriers: A proof of concept with pn-

junctions

17:30 – 18:00 Masahiro Sasaki (TREMS, Tsukuba)

Unusual Features of Field Electron Emission from Carbon Nanomaterials

19:00 Joint Dinner

November 5, 2019 (Tuesday)

Chairman: Junji Nakamura (TREMS, Tsukuba)

09:00 – 09:30 Takahiro Kondo (TREMS, Tsukuba)

Hydrogenated Borophene Sheets: Synthesis, Characterization, and

Application

09:30 – 10:00 Sven Reichenberger (CENIDE, UDE)

Pulsed laser post processing of transition metal oxides for catalysis

research applications

10:00 – 10:30 Kotaro Takeyasu (TREMS, Tsukuba)

Catalysts for CO2 conversion to ethanol and its mechanistic aspects

10:30 – 11:00 Coffee break

Chairman: Heiko Wende (CENIDE, UDE)

11:00 – 11:30 Malte Behrens (CENIDE, UDE)

Cobalt-iron catalysts for oxidation reactions

11:30 – 12:00 Sven Anke (Ruhr-University Bochum)

Unsupported Cobalt-based Spinel Nanoparticles Applied in 2-Propanol

Gas-Phase Oxidation

12:00 – 12:30 Soma Salomon (CENIDE, UDE)

Element-specific measurements on mixed-oxide catalysts

AGENDA 5

12:30 – 12:45 Group photo

12:45 – 13:30 Lunch and poster session

Chairman: Tatsuya Nabeshima (TREMS, Tsukuba)

13:30 – 14:00 Junji Nakamura (TREMS, Tsukuba)

Mechanism of oxygen reduction reaction on N-doped carbon catalysts

14:00 – 14:30 Baris Alkan (CENIDE, UDE)

Synthesis parameters, material characterization details of spray-flame

made LaCo1-xFexO3 perovskites

14:30 – 15:00 Eiji Nishibori (TREMS, Tsukuba)

In-situ SR diffraction study of hydrothermal nano-particle synthesis

15:00 – 15:30 Coffee break

Chairman: Nicolas Wöhrl (CENIDE, UDE)

15:30 – 16:00 Tatsuya Nabeshima (TREMS, Tsukuba)

Creation of Unique Structures and Functions by Utilizing Coordination

Bonds

16:00 – 16:30 Masaki Hada (TREMS, Tsukuba)

Ultrafast structural dynamics for energy materials

16:30 – 17:00 Frank Meyer zu Heringdorf (CENIDE, UDE)

Nonlinear Electron Emission from Strong Surface Plasmon Polaritons

17:00 – 17:30 Malte Behrens (Deputy Scientific Director CENIDE, Speaker CRC/TRR

247, UDE)

Takaki Kanbara (Director TREMS, Tsukuba)

Closing remarks

TALKS 7

Direct arylation polycondensation: Facile access to semiconducting polymers

Takaki Kanbara

Tsukuba Research Center for Energy Materials Science (TREMS),

Graduate School of Pure and Applied Sciences, University of Tsukuba

E-Mail: kanbara@ims.tsukuba.ac.jp

Polycondensation via a dehydrohalogenative cross-coupling reaction, so-called direct arylation, has recently been recognized as an effective method for the practical synthesis of π-conjugated polymers [1-5]. This reaction eliminates the prior preparation of organometallicreagents and the treatment of metal containing byproducts, thereby decreasing the number of synthesis and purification steps required for the preparation of the monomers and polymers. Therefore, several groups have actively attempted to utilize this synthetic method for the synthesis of π-conjugated polymers to serve as semiconducting materials for optoelectronic devices. We have envisioned development of the direct arylation polycondensation as a general and reliable method. Expansion of this synthetic protocol allows for the polycondensation of various aromatic monomers [5,6]. This atom- and stepeconomical protocol also lends itself to practical application to fabrication of organic devises [7,8]. The improvement of the synthetic method is an important challenge for π-conjugated polymer materials to satisfy the demands of production costs and environmental issues for wide-scale practical applications. In this presentation, our recent activities on the facile synthetic protocol will also be presented [9-12].

[1] S. Kowalski, S. Allard, K. Zilberberg, T. Riedl, U. Scherf, Prog. Polym. Sci. 38, 1805 (2013). [2] S.-L. Suraru, J. A. Lee, C. K. Luscombe, ACS Macro Lett. 5, 724 (2016). [3] M. Wakioka, F. Ozawa, Asian J. Org. Chem. 7, 1206 (2018). [4] J. T. Blaskovits, M. Leclerc, Macromol. Rapid Commun. 40, 1800512 (2019). [5] J. Kuwabara, T. Kanbara, Bull. Chem. Soc. Jpn. 92, 152 (2019). [6] W. Lu, J. Kuwabara, T. Kanbara, Macromolecules 44, 1252 (2011). [7] J. Kuwabara, T. Yasuda, S. J. Choi, W. Lu, K. Yamazaki, S. Kagaya, L. Han, T. Kanbara, Adv. Funct.

Mater. 24, 3226 (2014). [8] J. Kuwabara, T. Yasuda, N. Takase, T. Kanbara, ACS Appl. Mater. Interfaces 8, 1752 (2016). [9] H. Saito, J. Chen, J. Kuwabara, T. Yasuda, T. Kanbara, Polym. Chem. 8, 3006 (2017). [10] H. Aoki, H. Saito, Y. Shimoyama, J. Kuwabara, T. Yasuda, T. Kanbara, ACS Macro Lett. 7, 90 (2018).

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[11] A. Ichige, H. Saito, J. Kuwabara, T. Yasuda, J.-C. Choi, T. Kanbara, Macromolecules 51, 6782 (2018). [12] H. Saito, J. Kuwabara, T. Yasuda, T. Kanbara, Macromol. Rapid Commun. 39, 1800414 (2018).

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Self-Assembled Organic Semiconductor Microlasers and Microarrays

Yohei Yamamoto

University of Tsukuba

E-Mail: yamamoto@ims.tsukuba.ac.jp

Optical microcavities play an important role for the next-generation light technology. Recently, we succeeded in fabricating spherical microcavities from π-conjugated polymers (CPs) by simple self-assembly process (Fig. 1a).[1] We found that the microcavities exhibit whispering gallery mode (WGM) resonant photoluminescence (PL) upon focused laser excitation, where PL generated inside the sphere is confined via total internal reflection at the polymer/air interface.[2–12] The resonance occurs when the wavelength of the light is an integer multiple of the circumference of the microsphere. The CP-based microcavities have benefits to the conventional microcavities in the following points: (1) Simple and low-energy fabrication process to obtain well-defined microspheres (2) The microcavities act as both cavity and emitter (3) The microcavities possess high refractive index and photoabsorptivity (4) Potent use for electrically-driven WGM and laser oscillation. In this presentation, recent results on the fundamentals of the self-assembly of the CPs, resonant PL from the CP microspheres, intra- and intersphere light energy conversion, optically-pumped lasing (Fig. 1b), and the future prospects to realize light- and electrically-driven WGM and lasing will be presented.

[1] T. Adachi et al., J. Am. Chem. Soc. 2013, 135, 870−876. [2] K. Tabata et al., Sci. Rep. 2014, 4, 5902/1−5. [3] S. Kushida et al., Macromolecules 2015, 48, 3928−3933. [4] S. Kushida et al., ACS Nano 2016, 10, 5543–5549. [5] D. Okada et al., ACS Nano 2016, 10, 7058–7063. [6] D. Braam et al., Sci. Rep. 2016, 6, 19635/1–6. [7] Y. Yamamoto, Polym. J. 2016, 48, 1045–1050. [8] S. Kushida et al., Adv. Opt. Mater. 2017, 5, 1700123. [9] S. Kushida et al., J. Phys. Chem. Lett. 2017, 8, 4580–4586. [10] O. Oki et al., Mater. Chem. Front. 2018, 2, 270–274. [11] S. Nakajima et al., Chem. Commun. 2018, 54, 2534–2537. [12] D. Okada et al., Nano Lett. 2018, 18, 4396–4402.

Fig. 1: Schematic representation of the self-assembled conjugated polymer microspheres,

optical and SEM micrographs (a), and lasing spectra (b).

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TALKS 11

Scalable optoelectronic devices based on 2D semiconductors

Tilmar Kümmell1, Dominik Andrzejewski1, Ulrike Hutten1, Annika Grundmann3, Henrik Myja1, Eric Hopmann1, Leon Daniel1, Michael Heuken2,3, Holger Kalisch3, Andrei Vescan3, Gerd Bacher1

1 Werkstoffe der Elektrotechnik and CENIDE, Universität Duisburg-Essen, 47057 Duisburg, Germany

2 AIXTRON SE, 52134 Herzogenrath, Germany 3 Compound Semiconductor Technology, RWTH Aachen University, 52074 Aachen, Germany

E-Mail: tilmar.kuemmell@uni-due.de

Semiconducting transition metal dichalcogenides (TMDCs) represent a novel and sustainable material basis for ultrathin optoelectronic devices. While first device concepts were based mainly on exfoliated crystals, resulting in μm-sized prototypes, scalability is mandatory for industrially relevance. In our contribution, we present architectures for light emitters and light detectors in the mm² scale, based on 2D semiconductor layers grown by MOCVD. For emitters, we use a vertical p-n device layout [1] and demonstrate a scalable and reproducible process for light emitting devices based on TMDCs. WS2 monolayers with a direct bandgap in the red spectral range are grown in a commercial horizontal multi-wafer AIXTRON MOCVD reactor on sapphire (0001) substrates. After substrate removal, these TMDC monolayers are embedded between organic and inorganic injection layers on the anode and the cathode side, respectively. By applying increasing voltages, the devices show diode-like behavior and homogenous emission of red electroluminescence over an area of 6 mm², purely originating from the WS2 monolayer [2]. For photodetectors, TMDCs grown by MOCVD on sapphire are metallized with interdigital contact patterns, resulting in detection areas of 1 mm². We analyze the photocurrent under illumination with a defocussed laser (λ = 442 nm). Using MoS2 or WS2 monolayers for light detection, only very low responsivities below 1 mA/W are obtained. Interestingly, the efficiency is significantly higher for a directly grown MoS2/WS2-heterostructure on sapphire, where responsivities up to 16 A/W are achieved. We attribute this large gain to an effective carrier separation and photogating effect in the heterostructure. [1] D. Andrzejewski et al, Nanoscale 11, 8372 (2019) [2] D. Andrzejewski et al, ACS Photonics 6, 1832 (2019)

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Scalable, single-source, one-step synthesis of an electrocatalyst embedded in Carbon Nanowalls

Nicolas Wöhrl1, Sebastian Tigges1, Axel Lorke1

1University of Duisburg-Essen, Faculty of Physics and CENIDE, 47057 Duisburg, Germany

E-Mail: nicolas.woehrl@uni-due.de

A novel manufacturing method for the scalable, one-step synthesis of a Pt/C electro catalyst by inductively coupled plasma-enhanced chemical vapour deposition is presented. Platinum acetylacetonate is used to deposit platinum nanoparticles (NPs) and carbon nanowalls (CNWs) as support, simultaneously in a single, uncatalyzed process. The CNWs exhibit exceptional thermal as well as electrical conductivity and widely adjustable surface area, making them an ideal support for use in energy conversion applications. By adjusting certain process parameters, such as pressure, gas flow rate and temperature, the wall density and wall height of the CNWs, as well as the platinum loading and oxidation state of the resulting catalyst can be adjusted according to specific applications. Scanning electron microscopy and Raman spectroscopy are used to determine the CNWs’ structural and electronic properties, respectively. Additionally, X-ray photoelectron spectroscopy and Auger electron spectroscopy are used to determine the overall and spatially resolved chemical composition and oxidation state of the catalyst. High-resolution transmission electron microscopy (TEM) reveals a mean particle diameter below 3 nm, without agglomeration, and an exceptionally narrow particle distribution with a poly dispersity index below 0.1. Furthermore, due to the simultaneous synthesis of both NPs and support, the nanoparticles are incorporated into the C-matrix, which is supported by TEM tomography. Such incorporation is improving the immobilization of NPs on the support and thus the long-term stability of the catalyst. Finally, due to the use of a metal-organic precursor, the process can be adjusted to deposit almost any metal/CNW-hybrid material.

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Temperature-induced transformation in CuO/MgO and CuO/ZnO pre-catalysts studied by in situ XRD and TEM

Oleg Prymak1, Gereon Behrendt1, Anna Rabe1, Andreas Hüttner1, Malte Behrens1

1Institute of Inorganic Chemistry and Center for Nanointegration Duisburg-Essen (CeNIDE), University of

Duisburg-Essen, Universitaetsstr. 5-7, 45117 Essen, Germany

E-Mail: oleg.prymak@uni-due.de

Cu/ZnO/(Al2O3) catalysts are employed in the industrial methanol synthesis due to the active surface defects of Cu and partially reduced Zn species at the surface [1]. The synergetic role of ZnO is assumed to originate from strong metal-support interaction (SMSI) and can be investigated by replacing it with MgO [2]. In both cases Cu/ZnO and Cu/MgO nanoparticles with suitable morphology can be produced by thermal decomposition of co-precipitated hydroxy-carbonate precursors. In this work, we investigated temperature-induced transformation of crystalline (Cu,M)CO3(OH)2 (M = Zn, Mg) precursors into CuO/ZnO (CZ) and CuO/MgO (CM) pre-catalysts by transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), thermogravimetric analysis (TGA) and X-ray powder diffraction in situ (XRD). The zincian malachite (M = Zn) and mcguinnessite precursors (M = Mg) were calcined at 400 and 700 °C. For detailed analysis, extended crystallographic investigation by XRD in situ in the temperature range of 25-400° under air with a precise determination of the lattice parameters and the crystallite size was performed by Rietveld refinement. Both TEM and XRD results confirmed the formation of crystalline CuO in CZ and CM. During this process the precursor crystallites are subjected to substantial shrinkage (Fig. 1, representatively shown for CM), while the initial needle-like morphology was preserved for the formed oxide aggregates at mild calcination at 400 °C. The decomposition temperature detected by XRD in situ agreed well with TGA. This morphology was destroyed at higher temperature at 700 °C.

Fig. 1: Crystallite (left) and particle (right) size determined by Rietveld refinement (XRD in situ) and microscopic investigation (TEM ex situ) of mcguinnessite precursors.

[1] M. Behrens, F. Studt, I. Kasatkin, S. Kühl, M. Hävecker, F. Abild-Pedersen, S. Zander, F. Girgsdies, P.

Kurr,B.-L.Kniep, M. Tovar, R. W. Fischer, J. K. Nørskov, R. Schlögl, Science 336, 893 (2012) [2] S. Zander, E. L. Kunkes, M. E. Schuster, J. Schumann, G. Weinberg, D. Teschner, N. Jacobsen, R.

Schlögl, M. Behrens, Angew. Chem. Int. Ed. 52, 6536 (2013)

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Trap Evaluation in MAPI thin films for photovoltaic applications

Svetlana Sirotinskaya1, Christian Fettkenhauer2, Daichi Okada3, Yohei Yamamoto3, Doru C.

Lupascu2, Roland Schmechel1 and Niels Benson1

1University of Duisburg-Essen, Faculty of Engineering, Institute of Technology for Nanostructures (NST) and

CENIDE, Bismarckstr. 81, 47057 Duisburg, Germany 2University of Duisburg-Essen, Faculty of Engineering, Institute for Materials Science and CENIDE,

Universitätsstraße 15, 45141, Essen, Germany 3University of Tsukuba, Division of Materials Science, Faculty of Pure and Applied Sciences, 1-1-1

Tennodai, Tsukuba, Ibaraki 305-8573, Japan

E-Mail: niels.benson@uni-due..de

One of the reasons for the unprecedented success of the perovskite development for photovoltaic

applications, is the postulated beneficial trap physics in perovskite thin films. Yin et al. [1] described

this in a recent theoretical publication for the MAPbI3 system. The research suggests, that point

defects, as the major source for trap states in a perovskite crystal structure, mainly result in a density

of states distribution, which is close to, or within the perovskite transport states, making them

acceptable for solar cell operation. Further, experimental evidence by Edri et al. (Nano Lett., 14,

1000, 2014) indicates that grain boundaries in MAPbI3 thin films also do not have a negative

influence on the charge carrier transport.

Here we present a detailed experimental study on the grain boundary and bulk traps in MAPbI3,

which investigates these current mainly theoretical postulates. By using a combination of

experiments on µm-size crystallites as a model system and thin film devices, we are able to combine

the spatially resolved luminescence and structural information of analytical tools such as µ-PL and

µ-XPS, with the electrical information of MIS-TSC measurements. This allows us to substantiate a

comprehensive picture of the type of traps prevailing in MAPbI3, and to discuss their energetic trap

distribution and density. Therefore, with this study we are able to discuss the mainly theoretical ideas

of the trap physics in MAPbI3 and can partly confirm the existing ideas.

[1] W.-J. Yin, T. Shi and Y. Yan, Apl. Phys. Lett. 104, 063903 (2014).

[2] E. Edri, S. Kirmayer, A. Henning, S. Mukhopadhyay, K. Gartsmann, Y. Rosenwaks, G. Hodes and D.

Cahen, Nano Lett. 14, 1000 (2014).

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Tertiary battery for energy harvesting

Yutaka Moritomo1,2,3, Takayuki Shibata4, Yuya Fukuzumi1, Hiroki Iwaizumi1

1Graduate School of Pure & Applied Science, University of Tsukuba, Tennodai 1-1-1, Tsukuba,

Ibaraki 305-7571, Japan 2Faculty of Pure & Applied Science, University of Tsukuba, Tennodai 1-1-1, Tsukuba,

Ibaraki 305-7571, Japan 3Tsukuba Research Center for Energy Materials Science (TREMS), University of Tsukuba, Tsukuba,

Ibaraki 305-8571, Japan 4National Institute of Technology, Gunma College, Maebashi, Gunma, 371–8530, Japan

E-Mail: moritomo.yutaka.gf@u.tsukuba.ac.jp

An innovative energy harvesting technology, which converts waste heat near room temperature

and/or human body heat to electric energy at low cost and high efficiency, is required to realize a

smart society. Here, we proposed a new type of battery, that can be charged by the environmental

heat using the difference in the thermal coefficient (α = dV/dT) of the redox potential (V) between

the anode (αanode) and cathode (αcathode) materials. We call the battery “tertiary battery”, because it is

charged by the environmental heat, not by the electric energy.

The tertiary battery can produce electric energy in the thermal cycle between low (TL) and high (TH)

temperatures, making in sharp contract with the semiconductor-based thermoelectric device. In the

(a) warming process, the redox potentials of the anode and cathode change by αanodeT and

αcathodeT, respectively. We expect a thermally induced change in the cell voltage (Vcell) as large as

(α cathode -α anode)T. In other words, the environment heat put the tertiary battery in a charged state.

The stored electric energy can be extracted by the (b) discharge process at TH. During the (c) cooling

process, the redox potentials of the anode and cathode change by - αanodeT and - αcathodeT,

respectively. The stored electric energy can be extracted by the (d) discharge process at TL.

Therefore, searching and/or developing high-|α| materials is indispensable to enhance the thermal

efficiency () of the tertiary battery.

We fabricated a tertiary battery made of two kinds of cobalt Prussian blue analogues (PBAs) with

different α i.e., NaxCo[Fe(CN)6]0.71 (NCF71) and NaxCo[Fe(CN)6]0.90 (NCF90). The NCF71/NCF90

tertiary battery produces electric energy with = 1.0 % between TH (= 295 K) and TH (= 323 K). The

value is 11 % of the Carnot efficiency (H = 8.6 %). By replacing NCF71 with NaxMn[Fe(CN)6]0.83

(NMF83), we succeeded to increase to 2.3 % between TH (= 286 K) and TH (= 313 K). The value

is 27 % of the Carnot efficiency (H = 8.7 %).

[1] T. Shibata, Y. Fukuzumi, W. Kobayashi, Y. Moritomo, Appl. Phys. Express, 11, 017101 (2018).

[2] Y. Fukuzumi, K. Amaha, W. Kobayashi, H. Niwa, Y. Moritomo, Energy Technol., 6, 1865 (2018).

[3] T. Shibata, Y. Fukuzumi, Y. Moritomo, Sci. Reps, 8, 14784 (2018).

[4] H. Iwaizumi, Y. Fujiwara, Y. Fukuzumi, Y. Moritomo, Dalton Trans., 46, 1964 (2019).

[5] Y. Fukuzumi, Y. Hinuma, Y. Moritomo, AIP Adv., 8, 065021 (2018).

[6] Y. Fukuzumi, Y. Hinuma, Y. Moritomo, J. Phys. Soc. Jpn., 87, 055001 (2018).

[7] I. Takahara, T. Shibata, Y. Fukuzumi, and Y. Moritomo, Chem. Select, 4, 8558 (2019).

[8] H. Iwaizumi, T. Sugano, T. Yasuda, Y. Shimoi, W. Kobayashi, Y. Moritomo, Jpn. J. Appl. Phys., in press.

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Thermoelectrics with bipolar charge carriers: A proof of concept with pn-junctions

Franziska Maculewicz1, Timo Wagner1, Khaled Arzi2, Nils Hartmann3, Nils Weimann2,

Roland Schmechel1

1Institute of Technology for Nanostructures (NST), Faculty of Engineering & CENIDE, University of Duisburg-Essen (UDE), Bismarckstraße 81, 47057 Duisburg, Germany

2Components for High Frequency Electronics (BHE), Faculty of Engineering & CENIDE, University Duisburg-Essen (UDE), Lotharstrasse 55, 47057 Duisburg, Germany

3Interdisciplinary Center for Analytics on the Nanoscale (ICAN) & CENIDE, University of Duisburg-Essen (UDE), Carl-Benz-Str. 199, 47057 Duisburg, Germany

E-Mail: roland.schmechel@uni-due.de

The direct conversion of heat fluxes into electricity are usually considered if robustness, integrability or miniaturizability are more important than efficiency. Thermoelectrics (TE) and thermophotovoltaics (TPV) are quite often considered for that [1]. Energy harvesting for self-sustained sensors or utilization of waste heat in steel and glass industry are typical application scenarios beside special applications in the space and military technology. Since conventional TE is a unipolar phenomenon, which is based on the thermal diffusion of majority charge carriers, it is limited when the material becomes intrinsic and the thermoelectric contribution of positive and negative charge carriers cancel out each other. The separation of ambipolar diffusing charge carriers in the space charge region of a pn-junction would allow to harvest the energy, carried by the bipolar charge carriers. The idea was theoretically predicted already 12 years ago, but has never been proven experimentally. Therefore, a p-i-n structure were investigated within a temperature gradient along the junction [2]. The conventional thermoelectric effect in the p- and n-regions had to be suppressed by short circuiting the p- and n-regions. The remaining potential difference across the p-i-n structure without external bias is assigned to the separation of thermally excited charge carriers within the built-in field in the i-region. The different nature of both thermal charge separation processes is underlined by the fact, that the conventional thermoelectric effect across intrinsic silicon shows a zero crossing, due to a change from p-type (due to residual p-doping) to n-type (intrinsic, but higher electron mobility), while the output power of the p-i-n structure increases monotonically with temperature. The experiments were accompanied with numerical device simulations based on a drift-diffusion-model. While this first experimental proof provides just a small power output, it is the goal to cultivate this effect in new device designs. [1] Irene Ambo Okanimba Tedah et. Al., J. Phys. D: Appl. Phys. 52 2755012019 (2019). (doi.org/10.1088/1361-6463/ab1833) [2] F. Maculewicz et. Al., J. Appl. Phys. 125, 184502 (2019) (doi: 10.1063/1.5081998).

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Unusual Features of Field Electron Emission from Carbon

Nanomaterials

Masahiro Sasaki

Tsukuba Research Center for Energy Materials Science (TREMS) and Faculty of Pure and Applied

Sciences, University of Tsukuba

E-Mail: sasaki@bk.tsukuba.ac.jp

At the beginning, I will introduce the overall activity on electronic device fabrication and material

nano-characterization in the electric energy control division of TREMS. After that I will present the

study in our group on the field electron emission from carbon nanomaterials.

Carbon nanomaterials such as graphene, fullerene, carbon nanotubes and their related materials

are known to possess quite various and unique electronical properties. Thus, these materials have

attracted much attention of lots of researchers. On the other hands, these materials show unique

features also on field electron emission, where the mechanism is not well known. Although carbon

nanotubes may be attractive for field emitters due to their intrinsic extremely sharp shape, largely

lowering the threshold applied voltage, here I would like to present unusual features of field emission

from other carbon nanomaterials such as arc-prepared carbon, carbonized pencil lead, and

fullerene, which are not related to intrinsic geometrical field enhancement.

1. Arc-prepared carbon film In this study, carbon thin films were prepared by means of arc-discharge of graphite rods, which is

the simplest way to prepare carbon films. The W and Si tips covered with this carbon film give field

emission features corresponding to very low effective work function, although the macroscopic work

function of this film remains similar to that of graphite. The STM observations indicate that the film

consists of nm-scale amorphous carbon grains with different electronic properties, which enable to

effectively enhance electric field at so-called triple junctions between grains. Spontaneously

generated arrangements of nano-structures enhance electric field.

2. Edge of carbonized pencil lead The vertically broken and completely carbonized edges of pencil lead also show superior field

emission features, high current at very low applied fields, although the tips are not sharpened. Since

the energy distribution of emitted electrons is well reproduced by the density of states of graphene,

the superior field emission features may be originated from that of graphene. Native property of

graphene also can enhance electron emission.

3. Fullerene adsorbed on W tip We have observed that the C60 deposited W tip gives very unique field emission microscopy (FEM)

pattern, that is very similar to that of large atomic orbitals, corresponding to the super-atomic

molecular orbital (SAMO), which has been expected theoretically and proved by using STM. This

suggests that the electron orbital of unoccupied state can be visualized simply by using FEM. It is

known that weakly bound states can be hybridized and contributed to electron transport. We expect

FEM can be used to in-situ observe the hybridization of orbitals.

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Hydrogenated Borophene Sheets: Synthesis, Characterization, and Application

Takahiro Kondo

Faculty of Pure and Applied Sciences, University of Tsukuba, 305-8573, Japan

E-Mail: takahiro@ims.tsukuba.ac.jp

Two-dimensional (2D) materials consisting of a single or a few layers of atoms have superior performance compared to conventional materials or their bulk counterparts in a variety of applications, because of their unique properties, including their flexibility, high specific surface area, and quasi-2D electron confinement. Recently, we have revealed that the hydrogen boride (HB or borophane) sheets with an empirical formula of H1B1 can be formed by exfoliation and complete ion-exchange between protons and magnesium cations in magnesium diboride (MgB2) with an average yield of 42.3% at room temperature (Fig. 1a) [1], as a new member of boron-based nanomaterials [2]. The sheets feature an sp2-bonded boron planar structure without any long range order. A hexagonal boron network with bridge hydrogens is suggested as the possible local structure, where the absence of long range order was ascribed to the presence of three different anisotropic domains originating from the 2-fold symmetry of the hydrogen positions against the 6-fold symmetry of the boron networks, based on X-ray diffraction, X-ray atomic pair distribution functions, electron diffraction, transmission electron microscopy, photo absorption, core-level binding energy data, infrared absorption, electron energy loss spectroscopy, and density functional theory calculations. Our recent analysis with soft x-ray absorption and emission spectroscopy at the B K-shell also supports this view and show the semimetallicity of HB sheets [3]. We have then found several intriguing properties of HB sheets for the applications of hydrogen release [4], the reductant [5], and the solid-acid catalyst [6]. Figure 1b shows typical catalytic performance as a solid-acid, where C2H5OH is catalytically converted to C2H4 and water by the presence of HB sheets above c.a. 490 K, while no conversion occurs in the cases of B2O3 and MgB2. In the presentation, synthesis, characterization, and application of HB sheets will be introduced.

Fig. 1: (a) Schematic of HB synthesis (b) Ethanol conversion vs temperature

Acknowledgement: These works were done with Mr. H. Nishino, Prof. T. Fujita, Dr. N. T. Cuong, Dr. S. Tominaka, Prof. M. Miyauchi, Prof. S. Iimura, Dr. A. Hirata, Dr. N. Umezawa, Prof. S. Okada, Prof. E. Nishibori, Mr. A. Fujino, Mr. R. Ishibiki, Mr. T. Goto, Dr. S. Ito, Dr. Tateishi, Prof. Niibe, Prof. J. N. Kondo, Dr. T. Fujitani, Prof. I. Matsuda, Prof. J. Nakamura, and Prof. H. Hosono. [1] H. Nishino, T. Fujita, N. T. Cuong, S. Tominaka, et al., J. Am. Chem. Soc. 139, 13761 (2017). [2] T. Kondo, Sci. Technol. Adv. Mater. 18, 780 (2017). [3] I. Tateishi, N. T. Cuong, C. A. S. Moura, et al. Phys. Rev. Mate. 3, 024004 (2019). [4] R. Kawamura, N. Cuong, T. Fujita, R. Ishibiki, et al., Nature Communications, (2019) in press. [5] Japanese Patent Application No. 2019-42011 [6] A. Fujino, S. Ito, T. Goto, R. Ishibiki, J. Kondo, T. Fujitani, et al., ACS Omega, 4, 14100 (2019).

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Pulsed laser post-processing of transition metal oxides for catalysis research applications

Sven Reichenberger, Swen Zerebecki, Stephan Barcikowski

Technical Chemistry I and Center for Nanointegration Duisburg-Essen (CENIDE), Research Center for Nano

Energy Technology (NETZ), Duisburg, 47057, University of Duisburg-Essen, Germany

E-Mail: sven.reichenberger@uni-due.de

In the field of catalysis research and catalyst development, identifying and understanding structure-activity correlations in real-structure catalysts is essential for tailored catalyst design.1 To study the latter, catalyst materials with gradually tuned properties are needed. Pulsed Laser Post Processing (PLPP) in liquids has shown to be a promising tool to deliver such nanomaterials with increasingly altered properties (e.g. band gap or photo-luminescence) and consequently catalytic activities.2-5 Functionalization of catalysts with surfactant-free laser generated co-catalysts (e.g. Au NP) prior to PLPP5 enables further systematic studies of potential active sites present on the heterogenous catalyst during reaction. While a gradual tuning of materials properties is mainly achieved by controlling the number of laser pulses per particle (I. e. mass-specific energy dose, see Fig. 1), the transformation processes driven by each individual laser pulse will (considering constant laser pulse duration and wavelength) directly depend on the applied laser fluence being the main driving force. Consequently, fluence gradients known to occur in state of the art PLPP setups need to be avoided.4

Fig. 1: Effect of PLPP of P25-TiO2 (without and loaded with 1 wt% and 3 wt% of laser-generated Au

NPs) on the catalytic activity shown for a): Photocurrent density j in photocatalysis5 and b): Turn-over number (TONS) of ethanol to acetic acid during selective oxidation reaction2. Data are shown with respect to the number of laser irradiation cycles (Ncycle) applied. Figure was

taken from Ref. 2.

Within this presentation, a new flat-jet setup, minimizing the fluence gradient will be presented and

subsequently evaluated regarding the homogeneity of the PLPP process at the example of well-

established laser fragmentation of gold nanoparticles. Next, recent advances on laser-based

processing of oxidic nanomaterials using nano- and picosecond lasers and its implication for the

catalytic activity in different types of catalytic reactions will be presented and discussed.

[1] A. J. Medford, A. Vojvodic, J. S. Hummelshøj, J. Voss, F. Abild-Pedersen, F. Studt, T. Bligaard,

A. Nilsson, and J. K. Nørskov, Journal of Catalysis, vol. 328, pp. 36–42, (2015).

[2] S. Reichenberger, G. Marzun, M. Muhler, S. Barcikowski, ChemCatChem. 11 (18), 4489, (2019).

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[3] M. Lau, S. Barcikowski, Appl. Surf. Sci., 348, 22–29 (2015). [4] F. Waag, B. Goekce, C. Kalapu, G. Bendt, S. Salamon, J. Landers, U. Hagemann, M. Heidelmann, S.

Schulz, H. Wende, N Hartmann, M. Behrens, S. Barcikowski, Scientific Reports, 7, 1-13, (2017).

[5] M. Lau, S. Reichenberger, I. Haxhiaj, S. Barcikowski, A. M. Müller, ACS Applied Energy Materials 1,

5366−5385, (2018).

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Catalysts for CO2 conversion to ethanol and its mechanistic aspects

Kotaro Takeyasu1,2, Bappi Paul1, Ryuichi Saito1,2, Tadahiro Fujitani1,3, Junji Nakamura1,2

1Faculty of pure and applied sciences, University of Tsukuba 2Tsukuba Research Center for Energy Materials Science

3National Institute of Advanced Industrial Science and Technology

E-Mail: takeyasu.kotaro.gt@u.tsukuba.ac.jp

For chemical recycling of CO2, lowering of the hydrogenation temperature is one of the largest targets because the cost-cut for the heating of reactors and the increase of equilibrium conversion rate is insufficient. The other challenge is to directly synthesize ethanol which has high usability and renewability. Several studies recently reported direct synthesizes of ethanol from CO2 at a reaction temperature of ~150 oC1). The common reaction conditions are to use more than two metals for the catalysts and to add water or the other solvents of ~1 ml. Although the reaction mechanisms were not proposed, a local electrochemical reaction possibly occurs, which is proposed for three-way catalytic reactions and oxidation of hydrocarbons2). We aim to verify electrochemical effects in the ethanol and methanol synthesis at the relative low temperature and the detailed reaction mechanisms. For the evaluation of the total catalytic activities, Pd/Cu and Ru/CoOx catalysts were synthesized. CO2/H2 gas of 4 MPa and H2O of 1 ml were input in a reactor along with the catalysts of 40 mg and the reaction temperature was set to be 150 ℃. Figure 1 shows a gas chromatogram of the products with the Ru/CoOx catalyst after a retention time of 15 h. The peaks at 6.7, 8.1, 13.8, and 15.6 min correspond to methanol, ethanol, 1-propanol, and 1-butanol, respectively. Figure 2 shows the production yields as a function of time. The continuous production yields indicate the working of the catalytic reactions. For the observation of electrochemical processes, Ru and CoOx catalysts were separately deposited on the different electrodes in a reactor which were connected to a potentiostat. Negative reaction currents were observed as CO2/H2 gas was introduced into the reactor at room temperature, which indicates that oxidation and reduction reactions occur on each electrode. The result suggests that the oxidation of H2 and the reduction of CO2 also take place separately on the Ru/CoOx catalyst. We also would like to discuss energetic efficiency of local electrochemical reactions comparing it with that for thermal reactions.

[1] Z. He et al., Angew. Chem. Int. Ed. 55, 737 (2016)., S. Bai et al., JACS 139, 6827 (2017).

[2] Y. Hernandez et al., Catal. Today 241, 143 (2015), T. Hibino et al., J. Electrochem. 161, H326 (2014).

Fig. 1: A gas chromatogram of products from

H2/CO2 gas of 4 MPa with a catalyst of Ru/CoOx.

Fig. 2: The production yields

as a function time

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Cobalt-Iron Catalysts for Oxidation Reactions

Anna Rabe1, Malte Behrens1,2

1University of Duisburg-Essen (UDE), Faculty of Chemistry and CENIDE, Essen

2UA Ruhr Professor for Materials Chemistry of Catalysts at UDE and Ruhr-University Bochum

E-Mail: malte.behrens@uni-due.de

Heterogeneous oxidation catalysis is a key technology for a sustainable utilization of our resources

and for the challenges in chemical energy conversion. Despite this importance, in many cases there

is a lack of understanding, why a certain composition or microstructure of a catalyst works well. A

powerful approach to address these questions is the elucidation of correlation between structure

and composition with activity, selectivity and stability. Variation of the synthesis route for a given

catalyst or of selected synthesis parameters can lead to subtle differences in the micro- and defect

structure of nominally the same material. Examples from the field mixed cobalt-iron oxides will be

presented with a focus of effect of the synthesis route on the real structure of spinels and

perovskites. Co-precipitation syntheses and thermal post-treatment steps show how the particle

morphology can be governed by the crystalline co-precipitated precursor, for example in case of

layered double hydroxides (LDH).

LDHs prepared in aqueous media exhibited a platelet-like morphology in the micrometer range as

evidenced by SEM analysis (Fig. 1c). In contrast, isotropic nanoparticles with nearly threefold larger

surface areas were obtained following the microemulsion assisted co-precipitation route at constant

pH (Fig. 1b). This morphological uniqueness was observed irrespective of pH or co-precipitation

temperature variation. Interestingly, a systematic intensity loss of the (00l) reflections with

decreasing pH or T was observed, leading to almost complete disappearance under the mildest

synthesis conditions (Fig. 1a).

Fig. 1: (a) XRD patterns of the pH variation series (CoFe LDHs). (b) SEM images of conventional and

microemulsion-assisted (c) co-precipitated CoFe-LDHs (d) OER overpotential at 10 mA cm-2.

Electrocatalytic oxygen evolution reaction (OER) measurements revealed a reduction of the overpotential by nearly 15 % for the nanosized CoFe-LDHs in relation to the conventionally prepared samples (Fig. 1d). Interestingly, the performance remains almost unaffected upon calcination yielding spinels, which was only observed for the nanosized spinels obtained through the microemulsion approach. The presentation will also introduce the concepts and first results of the DFG-funded Collaborative

Research Centre 247 "Heterogeneous Oxidation Catalysis in the Liquid Phase" and the MERCUR-

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funded UA Ruhr project "Materials Chemistry of Catalysts" located at the Ruhr-University Bochum

and the University of Duisburg-Essen.

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Selective oxidation of 2-propanol over unsupported cobalt-based spinel

nanoparticles

Sven Anke1, Tobias Falk1, Georg Bendt2, Stephan Schulz2, Martin Muhler1

1Laboratory of Industrial Chemistry, Ruhr-University Bochum, Bochum, Germany 2Inorganic Chemistry, Universität Duisburg-Essen and Cenide, Essen, Germany

E-Mail: sven.anke@techem.rub.de

Unlike oxidation catalysts containing noble metals, mixed-metal oxides are less expensive and

exhibit higher resistance to poisoning and high thermal stability. Especially cobalt-based spinels are

considered promising in replacing commonly used oxidation catalysts in industrial applications like

the oxidation of CO or volatile organic compounds (VOCs).[1,2] They offer a great tunability of the

catalyst composition and related properties due to the presence of octahedral and tetrahedral sites

within the oxygen lattice, while the structure remains stable. Nevertheless, Co3O4 or CoFe2O4

catalysts can also deactivate during oxidation reactions due to coking.[3,4] Gaining insight in

deactivation is of crucial importance for the understanding of the reaction mechanism and the design

of superior catalysts. The selective oxidation of 2-propanol is applied as probe reaction for the redox

and acid-base properties of the spinels.

Cobalt oxide and cobalt ferrite were synthesized by using a colloidal one-pot method by

decomposition of M(acac)2 in the presence of oleyl amine followed by calcination at 573 K.[5] The

Co3O4 and CoFe2O4 nanoparticles were tested in the selective 2 propanol oxidation in a microreactor

set-up with a fixed-bed reactor and a calibrated QMS. The catalysts were oxidatively pretreated

(TPO) in 10% O2/He at 573 K prior to the oxidation reaction. Using a feed of 0.18% 2-propanol /

0.18% O2 / He (100 sccm), the catalysts (100 mg) were heated to 573 K with a heating rate of 0.5 K

min−1 under quasi steady-state conditions. DRIFT spectra were acquired with oxidatively pretreated

CoFe2O4 diluted with diamond powder (1:2) during (CH3)2CHOH dehydrogenation at 503 K for 30

min with subsequent desorption in inert gas.

The results of the catalytic 2-propanol oxidation conversion over Co3O4 and CoFe2O4 reveal that

both cobalt based oxides are highly active and selective in the oxidative dehydrogenation of 2-

propanol yielding acetone. Especially Co3O4 showed remarkable results reaching almost full

conversion with 100% selectivity to acetone at 430 K, but only during the first oxidation run.[6]

Various transient kinetic experiments indicate the selective character of involved surface lattice

oxygen. According to the DRIFT spectra of 2-propanol dehydrogenation supported by acetic acid

adsorption experiments, inhibition of the low-temperature reaction pathway is caused by acetate

species formed during unselective oxidation.[7] Carbonates are found to be spectators, whereas

TPO and XPS studies of the spent catalyst reveal additional carbon deposition causing further

deactivation.

[1] X. Xie, Y. Li, Z.-Q. Liu, M. Haruta, W. Shen, Nature 458, 746 (2009).

[2] S. Zafeiratos, T. Dintzer, D. Teschner, R. Blume, M. Hävecker, A. Knop-Gericke, R. Schlögl, J. Catal.

269, 309 (2010).

[3] O. Vozniuk, C. Bazzo, S. Albonetti, N. Tanchoux, F. Bosselet, J.-M. M. Millet, F. Di Renzo, F. Cavani,

ChemCatChem 9, 2219 (2017).

[4] L. Lukashuk, N. Yigit, R. Rameshan, E. Kolar, D. Teschner, M. Havecker, A. Knop-Gericke, R. Schlogl,

K. Fottinger, G. Rupprechter, ACS Catal. 6, 8630 (2018).

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[5] K. Chakrapani, G. Bendt, H. Hajiyani, I. Schwarzrock, T. Lunkenbein, S. Salamon, J. Landers, H. Wende,

R. Schlögl, R. Pentcheva, M. Behrens, S. Schulz, ChemCatChem 9, 2988 (2017).

[6] S. Anke, G. Bendt, I. Sinev, H. Hajiyani, H. Antoni, I. Zegkinoglou, H. Jeon, R. Pentcheva, B. Roldan

Cuenya, S. Schulz, M. Muhler, ACS Catal. 9, 5974 (2019).

[7] S. Anke, T. Falk, G. Bendt, I. Sinev, M. Hävecker, H. Antoni, I. Zegkinoglou, H. Jeon, A. Knop-Gericke,

R. Schlögl, B. Roldan Cuenya, S. Schulz, M. Muhler, to be submitted.

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Element-specific electronic and magnetic characterization of mixed-oxide catalysts

Soma Salamon, Heiko Wende

Faculty of Physics and Center for Nanointegration Duisburg-Essen (CENIDE), University of Duisburg-Essen

E-Mail: soma.salamon@uni-due.de

Mössbauer spectroscopy is utilized for an in-depth characterization of mixed-oxide catalysts, in order to provide detailed insights into their local electronic and magnetic properties, enabling a correlation of changes in hyperfine parameters with improvements in catalytic activities. The main focus lies on parameters such as the isomer shift, providing information on the valency and local surrounding of Fe-ions, as well as the degree of inversion in spinel systems. Latter allows a determination of the distribution of Fe and thus also other metal ions across different crystallographic sites in the spinel

lattice, which may have a direct influence on the catalytic performance of the respective system. By recording spectra at low temperatures (4.3K) and high applied magnetic fields (5T), we are able to systematically determine and evaluate the resulting hyperfine parameters, while also crosschecking our results via macroscopic measurement methods such as magnetometry. With this approach, we were able to correlate a change of the inversion parameter I (see Fig. 1) with improvements in catalytic activity, brought about by modification of the Co-Ni ratio in nanoparticles [1]. Further findings revolved around the enhancement of catalytic properties through pulsed laser fragmentation of cobalt ferrite nanoparticles [2], while also providing insights on the groundwork of synthesis procedures [3]. Plans for future measurements include Mössbauer spectroscopy at higher applied fields of 10T with the help of a new magnet cryostat, in order to more precisely determine the inversion parameter for samples of small nanoparticles. These would otherwise be difficult to evaluate due to strong spin canting, hindering the resolution of individual subspectra. Additionally, synchrotron-based methods (XMCD, EXAFS) will also be utilized to probe the magnetic states of other elements in addition to Fe.

[1] K. Chakrapani, G. Bendt, H. Hajiyani, I. Schwarzrock, T. Lunkenbein, S. Salamon, J. Landers, H. Wende,

R. Schlögl, R. Pentcheva, M. Behrens, S. Schulz ChemCatChem 9, 2988-2995 (2017) [2] K. Chakrapani, G. Bendt, H. Hajiyani, T. Lunkenbein, M. T. Greiner, L. Masliuk, S. Salamon, J. Landers,

R. Schlögl, H. Wende, R. Pentcheva, S. Schulz and M. Behrens ACS Catal. 8 (2), 1259-1267 (2018). [3] K. F. Ortega, S. Anke, S. Salamon, F. Özcan, J. Heese, C. Andronescu, J. Landers, H. Wende, W.

Schuhmann, M. Muhler, T. Lunkenbein and M. Behrens Chem. Eur. J. 23, 1-8 (2017).

Fig. 1: Mössbauer spectra of a Co-Ni

NP series recorded at 4.3K and 5T [1]

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Mechanism of oxygen reduction reaction on N-doped carbon catalysts

Junji Nakamura1,3, Riku Shibuya2, Santosh Singh1, Takahiro Kondo1,3, Kotaro Takeyasu1,3

1Department of Materials Science, Faculty of Pure and Applied Sciences, University of Tsukuba 2Graduate School of Pure and Applied Sciences, University of Tsukuba

3Tsukuba Research Center for Energy Materials Science (TREMS), University of Tsukuba

E-Mail: nakamura@ims.tsukuba.ac.jp

Nitrogen containing carbon materials have been reported to show catalytic activities such as an

oxygen reduction reaction (O2 + 4H+ + 4e- → 2H2O, ORR) in fuel cells. Among several types of

nitrogen species in carbon materials, pyridinic nitrogen (nitrogen atom bound to two C atoms) was found to create ORR active sites in our previous work1. We then try to prepare catalytically active carbon surfaces covered with pyridinic nitrogen-containing aromatic molecules with high density. Quite recently, we have reported model catalyst studies using HOPG (highly oriented pyrolytic graphite) electrode covered with pyridinic nitrogen-containing aromatic molecules (dibenz[a,c] acridine (DA) molecule and acridine (Ac)molecule)2. The DA molecules form a two-dimensional ordered structure along the direction of the HOPG substrate by self-organization. Adsorbed DA on the HOPG surface shows high ORR activity in terms of specific activity per pyridinic nitrogen and is comparable to that of pyridinic-nitrogen-doped carbon catalysts. We propose that the mechanism of ORR on the molecular model catalysts includes protonation of pyri-N and the following adsorption of O2 coupled with electron transfer. The hydrophobicity near the active site controls the activity since the hydrophobicity is related with the protonation step3.

[1] D. Guo, R. Shibuya, C. Akiba, S. Saji, T. Kondo, J. Nakamura, Science, 351, 361-365 (2016). [2] R. Shibuya, T. Kondo, J. Nakamura, ChemCatChem.10, 2019-2023 (2018). [3] S. Singh, K. Takeyasu, J. Nakamura, Advanced Materials, 1804297 (2018).

Fig. 2: (a) STM image of the DA/HOPG surface (Vs = -95 mV,

It = 3.1 nA). (b) Model structure of DA/HOPG. (c) Magnified

STM image of the DA molecule on HOPG. (d) HOMO of

isolated DA calculated using Gaussian. (e) Magnification of

the DA molecule in the model structure in Fig. 2b.

Fig. 1: ORR results for model

catalysts.

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Synthesis and characterization of La1-xSrxCo1-yFeyO3 nanoparticles for

water oxidation reaction

Baris Alkan1, Michael Braun2, Christof Schulz 1,3, Corina Andronescu2,3, Hartmut Wiggers1,3

1Institute for Combustion and Gas Dynamics – Reactive Fluids, University of Duisburg-Essen, Carl-Benz-Str.

199, 47057 Duisburg, Germany 2Chemical Technology III, Faculty of Chemistry, University Duisburg Essen,

Carl-Benz-Str. 199, 47057 Duisburg, Germany 3CENIDE, Center for Nanointegration Duisburg-Essen, University of Duisburg-Essen,

Carl-Benz-Str. 199, 47057 Duisburg, Germany

E-Mail: baris.alkan@uni-due.de

The improvement of the kinetics of oxygen evolution reactions (OER) through proper tuning of the

physical properties of electro- or thermal catalysts inherently depends on a synthesis method that

enables the production of high surface area catalysts – primarily nanoparticles with high phase

purity, minimum surface contamination, and high stability under the applied electric potential. We

utilized spray-flame synthesis as a suitable method to fulfill these criteria to synthesize transition

metal-based mixed-oxide perovskite nanoparticles. We produced La1-xSrxCo1–yFeyO3 perovskite

nanoparticles (x = 0.1 and 0.2, y= 0 and 0.2) and tested their material and catalytic activity toward

OER reactions.

Accordingly, the as-prepared nanoparticles were found to have homogenous nanoparticle size

distribution with the mean particle sizes about 8-10 nm. HAADF STEM analyses demonstrate that

all nanoparticles have crystalline perovskite bulk structure, while surface defective regions were also

noticed in Sr-substituted particles. At high Sr content, the stacking faults and antiphase boundaries

were found in the bulk structure of perovskite, and the formation of these defects were associated

with inhomogeneous distribution of Sr substitutes. In addition, qualitative phase and infrared spectral

analyses revealed that the materials consist of both stoichiometric and oxygen-deficient perovskite

phases, and contain low degree of combustion residuals. Thermal analyses determined that the

combustion residuals are comprised mainly from water and carbonate groups, and Sr substitution

into LaCoO3 especially triggers carbonate formation. Moreover, XPS analyses pointed out that the

content of surface Co2+ ions in the as-prepared materials increase with Sr substitution, while Co3+

ions are more favorable in Fe-substituted materials. The evaluation of OER catalytic activities of the

as-prepared nanoparticles indicated that 20 at. % Sr substituted materials distinctly show higher

OER activities (η ~ 330 mV) than the other materials, which show similar activities (η ~ 380 mV).

Overall, this study highlights that spray-flame made La1-xSrxCo1–yFeyO3 nanoparticles can be directly

used in the as-prepared state as OER catalysts, and the changes in crystal/atomic structure,

carbonation state, and the extent of Co2+ ions can be considered the critical factors influencing the

catalytic activities of these samples toward OER.

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In-situ SR diffraction study of hydrothermal nano-particle synthesis

Eiji Nishibori1, Tomoki Fujita1, Hidetaka Kasai1

1Fuculty of Pure and Applied Sciences and Tsukuba Research Center for Energy Materials Science, University of Tsukuba

E-Mail: nishibori.eiji.ga@u.tsukuba.ac.jp

Design and synthesis of size and shape controlled functional nano-particle have attracted attention owing to their huge potential for practical applications. Size and shape of nano-particle have been characterized by nano-meter scale probe, such as scanning and transmission electron microscopy, and X-ray and neutron diffraction. Among them, an X-ray is the most convenient and powerful probe owing to the transmittance of the sample cell, etc. We have designed a solvothermal reactor for nanoparticle synthesis and installed the reactor for in-situ synchrotron radiation powder diffraction experiment at SPring-8 BL02B2 beamline [1] (Figure 1). The reactor system has high reproducibility of data assisted by the oscillation measurement system with a vibrator which contributes to measure homogeneous intensity distribution of Debye-Scherrer ring. In-situ powder diffraction study of Ce(NO3)36H2O was described to show the performance of the reactor. Three dimensional diagram using pressure, temperature and particle size of CeO2 nanoparticles were determined by the system. The pressure and temperature dependence of particle formation speed, lattice constants, and particle size were clearly determined as a reproducible result. The present in-situ system [2] will be used to optimize synthesis condition for functional nano-particle.

Fig.1: Photograph of the reactor installed at SPring-8 BL02B2 beamline [1] S. Kawaguchi et al., Rev. Sci. Inst. 88, 085111, (2017). [2] T. Fujita et al., J. Supercrit. Fulids., 147, 172-178, (2019) .

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Creation of Unique Structures and Functions by Utilizing Coordination Bonds

Tatsuya Nabeshima1,2

1Department of Chemistry, University of Tsukuba, Tsukuba, Ibaraki 305-8571, Japan

2Tsukuba Research Center for Energy Materials Science, University of Tsukuba

E-Mail: nabesima@chem.tsukuba.ac.jp

Pseudomacrocycles and pseudmacrobicycles, whose frameworks are maintained by coordination

bonding, were synthesized for unique structures and functions.[1,2] A tripodal compound bearing a

bipyridine unit at the end of each chain reacted with Fe(II) as an effector to give the corresponding

bicyclic helical metallohost as a pseudocryptand. This helical molecules exhibited allosteric effects

on ion recognition. In addition, this helical structural motif can be used as a building block for the

construction of more sophisticated self-assembled molecular architectures on the basis of a

hierarchical strategy. Next, we discuss various derivatives of salamo (1,2-

bis(salicylideneaminooxy)ethane), saloph and salen ligands.[3-6] Not only a stable macrocyclic

trisalamo ligand but also acyclic oligosalamo derivatives were isolated as a stable species. The

acyclic bissalomo ligands exhibited very cooperative complexation ability toward Zn(II) to give C-

shaped helical homotrinuclear Zn complexes, which can be quantitatively converted to

heterotrinuclear Zn2•M (M=La, Ca, etc.) complexes. The helical sense of C-shaped multi-nuclear

salamo complexes was successfully controlled by external stimuli. We also created a multi-step-

helicity-switching system by using different metal ions for the complexation of a chiral salamo

derivative.

[1] T. Nabeshima, Synergy in Supramolecular Chemistry: T. Nabeshima, Ed.; CRC Press: New York, pp 1-

19 (2015).

[2] T. Nakamura, H. Kimura, T. Okuhara, M. Yamamura, T. Nabeshima, J. Am. Chem. Soc. 138, 794–797

(2016).

[3] S. Akine, T. Matsumoto, T. Nabeshima, Angew. Chem. Int. Ed. 55, 960-964 (2016).

[4] T. Nakamura, Y. Kaneko, E. Nishibori, T. Nabeshima, Nature Commun. 8, 129 (2017). [5] S. Sairenji, S. Akine, T. Nabeshima, Sci. Rep. 8, 137 (2018). [6] T. Nakamura, S. Tsukuda, T. Nabeshima, J. Am. Chem. Soc. 141, 6462-6467 (2019).

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Ultrafast structural dynamics for energy materials

Masaki Hada

Tsukuba Research Center for Interdisciplinary Materials Science (TREMS), Faculty of Pure and Applied

Sciences, University of Tsukuba, Tennodai 1-1-1, Tsukuba, 305-8573, Japan.

E-Mail: hada.masaki.fm@u.tsukuba.ac.jp

Ultrafast time-resolved electron diffraction provides structural information about the atomic

rearrangements during the phase transitions of materials or chemical reactions between molecules,

making it an ideal methodology for investigating photoinduced molecular motions. In this joint

symposium, our latest results [1,2] of ultrafast time-resolved electron diffraction measurements will

be given.

One of our latest achievements is the photo-reduction mechanism of graphene oxide revealed by

ultrafast time-resolved electron diffraction. Graphene oxide exhibits a broad range of potential

applications in view of the fact that the atomic structure and physical properties of its reduced form

resemble those of graphene, as well as it is dispersible in water and functionalized by chemical

methods. However, the structure of pristine graphene oxide and the nature of processes occurring

during its reduction have remained elusive. Herein, we employ ultrafast time-resolved electron

diffraction, ultrafast time-resolved spectroscopy, and time-dependent density functional theory

calculations to simultaneously elucidate the average structure of graphene oxide and observe its

reduction, precisely determining the relative contents and types of functional groups in the basal

plane. Our findings suggest that the oxygen atoms of epoxy groups are selectively removed from

the basal plane of graphene oxide by ultraviolet photoexcitation, in stark contrast to the behavior

observed for thermal excitation-based reduction.

[1] M. Hada, et al., Selective Reduction Mechanism of Graphene Oxide Driven by the Photon Mode versus

the Thermal Mode. ACS Nano 13, 10103-10112 (2019).

[2] M. Hada, et al., Ultrafast isomerization-induced cooperative motions to higher molecular orientation in

smectic liquid-crystalline azobenzene molecules. Nature Communications 10, 4159 (2019).

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Nonlinear Electron Emission from Strong Surface Plasmon Polaritons

Frank Meyer zu Heringdorf

Faculty of Physics and CENIDE, University of Duisburg-Essen, Duisburg, Germany

Email: meyerzh@uni-due.de

Surface plasmon polaritons (SPPs) are collective oscillations of electrons at an interface between a noble metal surface and a dielectric material. SPPs can be excited by light, and by using focused ion beam milling for structuring of grating couplers, it is possible to control the starting location of SPPs with sub-wavelength precision and thus manipulate the shape of SPP phase-fronts at the nanoscale. A normal-incidence time-resolved photoemission electron microscopy (PEEM) experiment with <15 fs short laser pulses produces a direct conceptual visualization of the excited fs SPP pulses and provides for imaging of propagating and interfering SPP pulses in space and time. In transient standing-wave SPP fields, an unexpected time-signature of the nonlinear photoemission yield is observed. By employing a transit-time separation of the exciting laser pulse from the SPP, the electron emission must be explained exclusively with the SPP field (plasmoemission). Using circular grating couplers, small SPP focus spots can be formed, from which highly nonlinear above threshold (plasmo)electron emission is observed. SPPs with angular orbital momentum can create even stronger fields in a SPP focus. The analytical solutions for SPPs excited at an Archimedean spiral show that for a total angular momentum of J=0 a defined focus spot with a transverse SPP field is obtained. In such focus spots, the plasmoemission mechanism is gradually driven into the strong-field regime.

TALKS 48

POSTERS 49

List of poster presentations

(1) Steven Angel, Michael Braun, Corina Andronescu, Christof Schulz, Hartmut Wiggers

Spray-flame synthesis of LaFexCo1−xO3 (x = 0.1, 0.2, and 0.3) perovskites made from

metal acetate and nitrate solutions for OER

(2) Aswin Asaithambi, Roland Kozubek, Guenther Prinz, Francesso Reale, Cecelia

Mattevi, Marika Schleberger, and Axel Lorke

Defect engineering in WS2 monolayers

(3) Gereon Behrendt, Jil Gieser, Andreas Huttner, Klaus Friedel Ortega, Malte Behrens

Malachite-based catalyst precursors for methanol synthesis from CO2-rich synthesis

gas

(4) Michael Braun, Andreas Hüttner, João Junqueira, Jonas Weidner, Wolfgang

Schuhmann, Malte Behrens, Corina Andronescu

Selective Electrooxidation of Glycerol on mixed Nickel Cobalt Hydoxy-Carbonates

(5) Yuya Fukuzumi, Yoyo Hinuma, Yutaka Moritomo

3d-electron configuration entropy effect on temperature coefficient of redox potential

of Prussian blue analogues

(6) Kohei Iwai, Hiroshi Yamagishi, Hayato Tsuji, Ken Albrecht, Fumio Sasaki, Hiroyasu

Sato, Yohei Yamamoto

Single-crystal optical microcavities from luminescent dendrimers

(7) Hiroki Iwaizumi, Yuya Fukuzumi, Yusuke Fujiwara, Yutaka Moritomo

Configuration entropy effect on temperature coefficient of redox potential of P2-

NaxCoO2

(8) Anna Rabe, Klaus Friedel Ortega und Malte Behrens

Impact of Microemulsion-assisted Co-precipitation at Constant pH on the

Electrocatalytic Efficiency of Layered Double Hydroxides

(9) Simon Schumacher, Tsvetan Tarnev, Michael Braun, Alan Savan, Lukas Madauß,

Alfred Ludwig, Marika Schleberger, Wolfgang Schuhmann, Corina Andronescu

Scanning Electrochemical Cell Microscopy – Investigation of the Hydrogen Evolution

Reaction on non-noble based electrocatalysts

(10) Ioannis Spanos, Marc F. Tesch, Mingquan Yu, Harun Tüysüz, Jian Zhang, Xinliang

Feng, Klaus Müllen, Robert Schlögl, Anna K. Mechler

A Facile Protocol for Alkaline Electrolyte Purification and Its Influence on a Ni−Co

Oxide Catalyst for the Oxygen Evolution Reaction

(11) Sebastian Tigges, Nicolas Wöhrl, Ivan Radev, Ulrich Hagemann, Markus

Heidelmann, Thai Binh Nguyen, Stanislav Gorelkov, Stephan Schulz, Axel Lorke

Scalable, Single-source, One-step Synthesis of Electrocatalysts

(12) Swen Zerebecki, Eko Budiyanto, Harun Tüysüz, Friedrich Waag, Stephan

Barcikowski, Sven Reichenberger

Catalytic activity improvement of Co3O4 by continuous Pulsed Laser Post Processing

(PLPP) in a flat-jet setup

Contact

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