Multiphysics Modeling of Gas Diffusion Electrodes for CO2 Reduction

One of the main challenges towards achieving high efficiency solar fuel generators performing carbon dioxide reduction is the mass transport limitations in traditional aqueous systems. Typically, the current density for liquid phase carbon dioxide reduction is limited to approximately 10 mA/cm 2 due to concentration polarization near the cathode surface. 1 This can be overcome by introducing a gas diffusion electrode, which allows vapor phase carbon dioxide to be fed directly to the catalyst, significantly decreasing the diffusion length. Experiments have shown almost two orders of magnitude improvement in efficiency for vapor-fed devices compared to traditional aqueous systems. 2,3 This improvement is most likely due to a higher surface area in the porous electrode and an increased diffusivity of gas phase CO 2 . For this work, we have developed a multiphysics model for gas diffusion electrodes that simulates species transport in gas phase, liquid phase and solid phase, charge transport, and (electro)chemical reaction kinetics. The model will focus on understanding transport of species in and out of the catalyst layer, and investigate the effects of gas diffusion electrode properties such as thickness, porosity and hydrophobicity on cell performance. Acknowledgements This material is based upon work performed by the Joint Center for Artificial Photosynthesis, a DOE Energy Innovation Hub, supported through the Office of Science of the U.S. Department of Energy under Award Number DE-SC0004993. References Singh, M. R.; Clark, E. L.; Bell, A. T., Physical Chemistry Chemical Physics , 2015 , 17(29), 18924-36. Verma, S.; Lu, X.; Ma, S.; Masel, R. I.; Kenis, P. J. A., Physical Chemistry Chemical Physics , 2015 , 18, 7075-7084. Kim, B.; Hillman, F.; Ariyoshi, M.; Fujikawa, S.; Kenis, P. J. A., Journal of Power Sources , 2016 , 312, 192-198.