Upload
others
View
4
Download
0
Embed Size (px)
Citation preview
S-1
Supporting Information
Self-supported Ni(OH)2/MnO2 on CFP as a Flexible Anode
towards Electrocatalytic Urea Conversion: the Role of
Composition on Activity, Redox States and Reaction
Dynamics
Jianfang Menga, Petko Chernev
b, Mohammad Reza Mohammadi
b, Katharina Klingan
b, Stefan
Loosb,d
, Chiara Pasquinib, Paul Kubella
b, Shan Jiang
b, Xianjin Yang
a,c, Zhenduo Cui
a, Shengli
Zhua,c
, Zhaoyang Lia,c
, Yanqin Lianga,c
,Holger Daub
aSchool of Materials Science and Engineering, Tianjin University, Tianjin 300072, China
bDepartment of Physics, Free University of Berlin, Arnimallee 14, 14195, Berlin, Germany
cTianjin Key Laboratory of Composite and Functional Materials, Tianjin 300072, China
dFraunhofer Institute for Manufacturing Technology and Advanced Materials (IFAM)
Winterbergstraße 28, 01277 Dresden, Germany
*Corresponding author. E-mail: [email protected] (Y. Q. Liang), [email protected]
(H. Dau)
S-2
Fig. S1 SEM images of (a) CFP-NiMn1.4 and (b) CFP-NiMn4.0.
Fig.S2 XRD patterns of MnO2 powder and CFP-NiMn2.4.
S-3
Fig.S3 (a) XPS spectrum of CFP-NiMn2.4. High resolution spectra of (b) O 1s, (c) Ni
2p, (d) Mn 2p, and (e) XPS spectrum of CFP-Mn2 and high resolution spectra of (f)
Mn 2p, the inset in (d) is the enlarged spectra of Mn 2p2/3 of CFP-NiMn2.4 (black) and
CFP-Mn2 (red).
X-ray photoelectron spectra detect signals from Mn, Ni, C and O elements. The
elemental manganese and nickel are generated from MnO2 and the Ni(OH)2,
respectively. The two signals at 642.4 eV for Mn 2p3/2 and 653.9 eV for Mn 2p1/2
observed in CFP-Mn2, are characteristic of MnO2. Moreover, the small shift of Mn
2p3/2 peak to lower binding energy (642.2 eV) is observed after Ni deposition, most
possibly caused by the electrochemical reduction of Mn species, which is accordance
with XAS result. But due to the susceptibility of Mn-oxide materials, we cannot rule
S-4
out the possibility of other forms of charging path inducing to the tiny shift in binding
energy.1-2
The Ni(OH)2 state is confirmed by principal peaks at 855.5 eV in high-
resolution Ni 2p XPS spectrum. The spectra of O 1s further confirm the existence of
MnO2 (530.0 eV) and Ni(OH)2 (531.2 eV).
Fig. S4 Cyclic voltammogram of CFP-Mn1, CFP-Mn2, and CFP-Mn3 recorded in 1 M
KOH (a) and 1 M KOH&0.5 M urea (b).
Fig. S5 Tafel slopes obtained from quasi stationary measurements for OER in 1 M
KOH (a) and UOR in 1 M KOH&0.5 M urea (b)
S-5
Fig.S6 Nyquist plots of different catalysts for OER process at 1.70 V vs. RHE (a) and
for UOR process at 1.45 V vs. RHE (b).
Fig. S7 UOR stability performance for CFP-NiMn2.4. Galvanostation (V-t)
measurement performed at a constant current density of 10 mA cm-2
in 1M KOH and
0.5 M urea electrolyte over 10000 s.
S-6
Fig. S8 SEM image of CFP-NiMN2.4 catalyst after UOR glavanostation tests.
Fig. S9 Concentration of metals obtained from TXRF analysis before and after CV
electrochemical measurement.
S-7
Fig. S10 Relation between catalytic TOF value and one electron oxidation equivalent
(nred/(nNi+nMn) in percent) for CFP-Ni(OH)2, CFP-NiMn1.4, CFP-NiMn2.4, and CFP-
NiMn4.0 after operation in KOH (a) and KOH&urea (b). Catalyst loadings (nNi+nMn)
were determined by TXRF analysis after measurements. Turnover frequency (TOF)
of CFP-NiMn catalysts based on the total metal loading of Ni+Mn extracted from
steady state current densities in KOH at 1.65 V vs. RHE, and in KOH&urea at 1.51 V
vs. RHE (only based on Ni metal loading molar quantity).
S-8
Fig. S11 (a) The schematic diagram of direct urea/O2 fuel cell configuration, (b) the
open circuit voltage of the cell tested by the multimeter.
S-9
Fig. S12 Extended X-ray absorption fine structure (EXAFS), (a) Mn K-edge of as-
prepared catalysts before and after conditioning in KOH and KOH&urea, (b) Ni K-
edge of as-prepared catalysts before and after conditioning in KOH and KOH&urea.
Catalysts were frozen under applied potential after conditioning at 1.627 V vs RHE
for 2 min.
S-10
Table S1. Parameters obtained by simulation of the k3-weighted EXAFS spectra for
Mn. The simulated spectra correspond to the Fourier-transformed EXAFS spectra
shown in Figure 3f, in which σ values for Mn-Mn shells are fixed. The errors
represent the 68% confidence interval of the respective fit parameter (N, coordination
number; R, absorber-backscatter distance; σ, Debye-Waller parameter; an amplitude-
reduction factor, S02=0.7)
N R [Å] σ [Å]
Mn2 Mn-O 5.6± 0.3 1.888±0.004 0.054±0.001
Mn-Mn, di-μ-
oxo
5.0± 0.3 2.868±0.004 0.059
Mn2-oper in
KOH
Mn-O 5.8± 0.3 1.897±0.004 0.059±0.001
Mn-Mn, di-μ-
oxo
5.8± 0.3 2.888±0.004 0.059
Mn2-oper in
KOH&urea
Mn-O 5.7± 0.3 1.892±0.004 0.051±0.001
Mn-Mn, di-μ-
oxo
5.6± 0.3 2.885±0.004 0.059
NiMn2.4 Mn-O 5.2± 0.3 1.896±0.004 0.051±0.001
Mn-Mn, di-μ-
oxo
5.0± 0.3 2.878±0.004 0.059
NiMn2.4-
oper in
KOH
Mn-O 5.8± 0.3 1.903±0.003 0.056±0.001
Mn-Mn, di-μ-
oxo
6.0± 0.3 2.892±0.002 0.059
NiMn2.4-
oper in
KOH&urea
Mn-O 5.8± 0.3 1.900±0.004 0.060±0.001
Mn-Mn, di-μ-
oxo
5.9± 0.3 2.898±0.004 0.059
S-11
References
(1) Kochur A. G., Kozakov A. T., Googlev K. A., Nikolskii A. V., Journal of Electron
Spectroscopy and Related Phenomena 2014, 195, 1-7.
(2) Ilton E. S., Post J. E., Heaney P. J., Ling F. T., Kerisit S. N., Applied Surface Science 2016,
366, 475-485.