Quaternary Oxide Photoanode Discovery Improves the Spectral Response and Photovoltage of Copper Vanadates

Copper vanadates are a promising class of solar fuel photoanodes with broad spectral response and excellent operational stability. The present performance limitations of these photoanodes are most evident in the rapid decrease in photoactivity with decrease in either photon energy or applied bias, the former limiting efficient utilization of the solar spectrum and the latter limiting photovoltage. We designed high-throughput photoelectrochemical screening to characterize these two aspects of improving Cu-V-based photoanodes in quaternary oxide composition spaces of the form Cu-V-X-O, where X = Mg, Ca, Sr, Fe. The results reveal that alloying of 2+ cations onto the Cu site of copper vanadates can improve photoelectrochemical properties, and Sr-alloyed Cu5V2O10 emerges as the most promising photoanode providing the best combination of photovoltage and spectral response. Six quaternary oxide phases are discovered as photoanodes with visible light activity below 1.23 V versus reversible hydrogen electrode, highlighting the high-throughput photoanode discovery.