(87k) Electrode Development in Alkaline Direct Ethanol Fuel Cells

Climate change and electricity consumption of the population have led to increasing interest in technologies that generate electricity from renewable sources. The use of sustainable ethanol in alkaline direct ethanol fuel cells (ADEFC) offers the advantages of easy storage and transport of the liquid fuel, low toxicity, environmental friendliness and robustness of these cells. Moreover, the alkaline environment in the ADEFC promotes the electrochemical reactions at the cathode and anode, and allows the use of platinum-free catalysts and low-cost anion exchange membranes. Besides challenges such as the incomplete conversion of ethanol (C-C cleavage issues), mixed potentials due to ethanol crossover and the durability of membranes, a high catalyst layer utilization of the electrodes needs to be achieved before commercialization.[1-4]

In this study, the effect of metal/carbon ratio of the anode catalyst and the influence of the layer thickness of both electrodes, anode and cathode, were investigated. Hence, thin-film rotating disk electrode (RDE) and half-cell gas diffusion electrode (GDE) experiments, as well as single cell tests were performed. Therefore, catalyst with different active material contents, electrodes with different layer thicknesses, and membrane electrode assemblies consisting of different catalysts and loadings were fabricated. The half-cell GDE and single-cell tests were conducted at different operating temperatures and conditions to determine the influence. Moreover, the produced electrodes were analysed with scanning electron microscopy. The reduction of metal content of the anodic catalysts resulted in more accessible metal particles and thus in a higher activity and performance and moreover in a cost reduction.[1] Furthermore, it could be shown that with half-cell GDE measurements, realistic reaction conditions, such as higher currents for the oxygen reduction reaction in comparison to RDE experiments, can be realized. The layer thickness influences the crossover through the membrane, as well as the catalyst layer utilization. High maximum power densities of 120 mW cm^-2 were obtained by determining the optimum layer thicknesses for the cathodic and anodic electrodes with Pt-free catalysts.[4] In addition, the investigations show potential further improvements of the electrodes for the commercialisation of the ADEFC.

The financial support from the Austrian Science Fund (FWF I 3871-N37) is acknowledged.

References

1. Roschger, S. Wolf, B. Genorio, V. Hacker. Effect of PdNiBi Metal Content: Cost Reduction in Alkaline Direct Ethanol Fuel Cells, Sustainability 14 (2022) 15485 (https://doi.org/https://doi.org/10.3390/su142215485)

2. Wolf, M. Roschger, B. Genorio, M. Kolar, D. Garstenauer, B. Bitschnau, V. Hacker. Ag-MnxOy on Graphene Oxide Derivatives as Oxygen Reduction Reaction Catalyst in Alkaline Direct Ethanol Fuel Cells, Catalysts 12 (2022) 780 (https://doi.org/10.3390/catal12070780)

3. Gorgieva, A. Osmić, S. Hribernik, M. Božič, J. Svete, V. Hacker, S. Wolf, B. Genorio. Efficient chitosan/nitrogen-doped reduced graphene oxide composite membranes for direct alkaline ethanol fuel cells, International Journal of Molecular Sciences 22 (2021) 1740 (https://doi.org/10.3390/ijms22041740)

4. Roschger, S. Wolf, K. Mayer, A. Billiani, B. Genorio, S. Gorgieva, V. Hacker. Influence of the electrocatalyst layer thickness on alkaline DEFC performance, Sustainable Energy and Fuels 7 (2023) 1093–1106 (https://doi.org/10.1039/d2se01729f)