Discovery of Fe-Ce Oxide/BiVO₄ Photoanodes through Combinatorial Exploration of Ni-Fe-Co-Ce Oxide Coatings

An efficient photoanode is a prerequisite for a viable solar fuels technology. The challenges to realizing an efficient photoanode include the integration of a semiconductor light absorber and a metal oxide electrocatalyst to optimize corrosion protection, light trapping, hole transport, and photocarrier recombination sites. To efficiently explore metal oxide coatings, we employ a high-throughput methodology wherein a uniform BiVO₄ film is coated with 858 unique metal oxide coatings covering a range of metal oxide loadings and the full (Ni-Fe-Co-Ce)O_x pseudoquaternary composition space. Photoelectrochemical characterization of the photoanodes reveals that specific combinations of metal oxide composition and loading provide up to a 13-fold increase in the maximum photoelectrochemical power generation for oxygen evolution in pH 13 electrolyte. Through mining of the high-throughput data we identify composition regions that form improved interfaces with BiVO₄. Of particular note, integrated photoanodes with catalyst compositions in the range Fe_(0.4-0.6)Ce_(0.6-0.4)O_x exhibit high interface quality and excellent photoelectrochemical power conversion. Scaled-up inkjet-printed electrodes and photoanodic electrodeposition of this composition on BiVO₄ confirms the discovery and the synthesis-independent interface improvement of (Fe-Ce)O_x coatings on BiVO₄.