(281d) Experimental Performance of Water-Splitting Photo-Electrodes Under High Solar Concentration

There have been few experimental reports of photo-electrochemical water splitting under high solar irradiance [1,2]. For hematite, it has been shown that illumination dependant charge transfer dynamics lead to the formation of long-lived holes and faster water oxidation kinetics with increasing photon flux [3], but these charge transfer dynamics have not yet been studied at higher concentrations (>30 suns). Here, we present an experimental setup for the testing of photo-electrochemical materials under high concentration (>100 suns peak) in EPFL’s high flux solar simulator. The key challenges of this novel experimental system are outlined, particularly on the issues related to thermal management and higher current densities. Sufficient heat transfer from the illuminated sample was achieved via forced convection and the design of a custom flow cell. Multiphysics modelling was conducted and compared to the experimental thermal performance of the cell. Finally, preliminary experimental results are shown with hematite samples due to their high stability and well-studied synthesis methods, and mechanisms for observed phenomena proposed. This experimental setup will facilitate the rapid testing of an array of photo-electrode materials (e.g. BiVO₄, LTON, etc.) allowing examination of the underlying physical phenomena under higher solar irradiance than previously achievable.

[1] Segev, G.; Dotan, H.; Malviya, K. D.; Kay, A.; Mayer, M. T.; Grätzel, M.; Rothschild, A. High Solar Flux Concentration Water Splitting with Hematite (α-Fe₂O₃) Photoanodes. Advanced Energy Materials 2016, 6 (1), 1500817. https://doi.org/10.1002/aenm.201500817.

[2] Vilanova, A.; Dias, P.; Azevedo, J.; Wullenkord, M.; Spenke, C.; Lopes, T.; Mendes, A. Solar Water Splitting under Natural Concentrated Sunlight Using a 200 cm² Photoelectrochemical-Photovoltaic Device. Journal of Power Sources 2020, 454, 227890. https://doi.org/10.1016/j.jpowsour.2020.227890.

[3] Le Formal, F.; Pastor, E.; Tilley, S. D.; Mesa, C. A.; Pendlebury, S. R.; Grätzel, M.; Durrant, J. R. Rate Law Analysis of Water Oxidation on a Hematite Surface. Journal of the American Chemical Society 2015, 137 (20), 6629–6637. https://doi.org/10.1021/jacs.5b02576.