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PdxRu1-X, electro-catalyst in direct alkaline ethanol fuel cells Alixia Farrell; Evans Monyoncho[1]; Elena A. Baranova[1]
[1] Department of Chemical and Biological Engineering, Center for Catalysis Research and Innovation (CCRI) University of Ottawa, Ottawa, ON K1N 6N5, Canada
Direct Ethanol fuel cells (DEFCs) are promising candidates. They have a higher energy density, their materials are more available and their handling is easier than the hydrogen based fuel cells. This technology is not yet perfected due to the inef?icient electro-‐oxidation of the ethanol. The factors addressed by this research is the choice of electro-‐catalyst and the concentration of ethanol provided to the reaction. The development of a catalyst that can fully decompose ethanol into water and CO2 to release the maximum of energy will permit the ethanol-‐based fuel cell to be a viable and ef?icient source of energy in the future.
Abstract
Objective Increase the current density produced by the reaction while reducing the onset potential by testing certain ratios of Pd and Ru as electro-‐catalyst and various concentrations of ethanol to be oxidized.
Methodology
Results
Catalyst Mass of Pd on electrode
(mg) ESCA (cm2)
Anodic E (V) Anodic I (mA cm-‐2)
E Onset Ep1 Ep2 Ip I at -‐0.96 V Pd/C 0.00461 0.153714 -‐0.97 -‐0.659 -‐-‐-‐-‐-‐ 2.279 0.018834 PdRu/C 50-‐50 0.00237 0.648762 -‐1.28 -‐0.676 -‐0.897 0.201 0.12142 PdRu/C 80-‐20 0.00394 0.581447 -‐1.23 -‐0.793 -‐1.066 0.626 0.228561 PdRu/C 90-‐10 0.00498 0.916623 -‐1.19 -‐0.623 -‐-‐-‐-‐-‐ 1.263 0.21276 PdRu/C 95-‐5 0.00440 0.19611 -‐1.21 -‐0.635 -‐-‐-‐-‐-‐ 0.568 0.022922 PdRu/C 99-‐1 0.00455 0.539421 -‐1.19 -‐0.65 -‐-‐-‐-‐-‐ 3.028 0.154533
Fig. 1: Method of synthesis
Discussion
Future Work
Acknowledgments
References
• Electrochemical Surface Area (ECSA) varies on the preparation and application of the catalyst
• Electrochemical activity is optimal at a set potential of -‐0.96 V. Any lower potential (-‐1.06 V) reduces the activity to almost no current in the long term.
• Presence of Ru as catalyst enhancer increases current intensity overall. Higher ratios of Ru decrease onset potential.
• Current intensity is optimized at a PdRu atomic ratio of 90:10 but PdRu 50:50 has the lowest onset potential.
• Ethanol concentration increases electrochemical activity up to a peak of 1 M EtOH. Any higher concentration of EtOH decreases current intensity.
Conclusion
0 1000 2000 3000 4000 5000 6000
0.00
0.05
0.10
0.15
0.20
C A s for P dxR u
1-‐x/C s amples in 1M K O H+1M E tO H
I/mA cm
-‐2
time/s
P d P dR u 50-‐50 P dR u 80-‐20 P dR u 90-‐10 P dR u 95-‐5 P dR u 99-‐1I/mA cm-‐2 at 3000 s
P d -‐0.018399:1 0.014595:5 0.013590:10 0.023980:20 0.019750:50 0.0171
E = -‐0.96 V
0 1000 2000 3000 4000
0.0
0.2
C A s for va rious [E tO H ] in 1M K O H us ing P d95R u
5/C a t E = -‐0.96V
I/mA cm
-‐2
time/s
0 .1 M 0.4M 0.6 M 0.8 M 1M 1.5 M 2 M 3 M
I/mAcm2 at 3000s0.1 M 0.002750.4 M 0.02510.6 M 0.04150.8 M 0.03911.0 M 0.06851.5 M 0.06132.0 M 0.04643.0 M 0.0477
-‐1.6 -‐1.4 -‐1.2 -‐1.0 -‐0.8 -‐0.6 -‐0.4
-‐0.20
-‐0.15
-‐0.10
-‐0.05
0.00
0.05
0.10
0.15
0.20
0.25
-‐1.6 -‐1.4 -‐1.2 -‐1.0 -‐0.8 -‐0.6 -‐0.4
-‐0.4
-‐0.3
-‐0.2
-‐0.1
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
-‐1.6 -‐1.4 -‐1.2 -‐1.0 -‐0.8 -‐0.6 -‐0.4-‐0.5
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
I/mA cm
-‐2
E we/V vs . MS E (V )
K O H 1M E tO H IM K O H 1M
P d50R u50/C
-‐1.28 V
I/mA cm
-‐2
E we/V vs . MS E (V )
K O H 1M E tO H IM K O H 1M
-‐1.23 V
P d80R u
20/C
I/mA cm
-‐2
E we/V vs . MS E (V )
K O H 1M E tO H IM K O H 1M
P d90R u
10/C
-‐1.19 V
-‐1.6 -‐1.4 -‐1.2 -‐1.0 -‐0.8 -‐0.6 -‐0.4
-‐0.15
-‐0.10
-‐0.05
0.00
0.05
0.10
0.15
-‐1.6 -‐1.4 -‐1.2 -‐1.0 -‐0.8 -‐0.6 -‐0.4-‐0.6
-‐0.4
-‐0.2
0.0
0.2
0.4
0.6
-‐1.6 -‐1.4 -‐1.2 -‐1.0 -‐0.8 -‐0.6 -‐0.4-‐1.5
-‐1.0
-‐0.5
0.0
0.5
1.0
1.5
P d95R u
5
I/mA cm
-‐2
E we/V vs MS E (V )
C yc le1 C yc le3 0.110 V
P d90R u
10
I/mA cm
-‐2
E we/V vs MS E (V )
C yc le1 C yc le3 0.561 V
P d80R u
20
I/mA cm
-‐2
E we/V vs MS E (V )
C yc le1 C yc le3
1.196 V
Fig. 6: CAs for PdxRu1-x/C samples in 1M KOH+1M EtOH at E=-0.96V
Fig. 7: CAs for various [EtOH] in 1M KOH using Pd95Ru5/C at E=-0.96V
• With highest consistent current intensity at a potential of -‐0.96 V and a low onset potential, Pd90Ru10/C proves to be one of the most effective combination. Pd80Ru20/C presents with a high intensity, a lower onset potential and a smaller loading of Pd which makes it cheaper than the Pd90Ru10/C and an equally viable option.
• 1M is the optimal concentration of ethanol in the electrolyte solution.
The next experiments will consist of testing the impact of ionic conductibility of the electrolyte by varying the KOH concentration. Also, spectroscopy will be used during the experiment in order to identify the intermediates products and understand their impact on the kinetics of the electrochemical reaction.
Fig. 8 : Direct Alkaline Methanol Fuel Cell1
Fig. 3 : Two-‐compartment-‐cell made of Te?lon used for experimentation
Experimentations: • Cyclicvoltammetry • Chronoamperommetry • CO Stripping
Fig 5: CVs of PdxRu1-x/C in 1M KOH (black curve) and 1M KOH+1M EtOH (red curve)
Fig. 4: CO stripping of PdxRu1-x/C in 1M KOH
Table 1: Electrochemical potentials and current intensities of PdxRu1-‐x catalysts measured by CV and CO Stripping
Fig. 2: Method of electrode preparation
(1)Yu, E. H.; Krewer, U.; Scott, K. Energies 2010, 3, 1499–1528. (2)Kamarudin, M. Z. F.; Kamarudin, S. K.; Masdar, M. S.; Daud, W. R. W. Int. J. Hydrog. Energy 2013, 38, 9438–9453. (3) Antolini, E.; Gonzalez, E. R. J. Power Sources 2010, 195, 3431–3450. (4) Ribadeneira, E.; Hoyos, B. A. J. Power Sources 2008, 180, 238–242. (5) Evans M. et al. Effect of Surface Structure on Catalytic Activity of PdxRu1- x/C Nanoparticles for Ethanol Electrooxidation, (To be submitted). 1 “Direct Methanol Alkaline Fuel Cell Simple”, 2011, http://vector.me/search/ engineering, viewed on January 21st 2014.
This research was supported by the University of Ottawa’s Undergraduate Research Opportunity Program (UROP).
Electrolyte
W.E C.E
NO2 CO
Excess Gas
R.E
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