Emerging Postsynthetic Improvements of BiVO₄ Photoanodes for Solar Water Splitting

Solar-assisted water splitting with bismuth vanadate (BiVO₄) photoanodes has progressed significantly with many efforts devoted to improving charge separation and surface charge injection through synthetic methods, including dopants and catalytic layers. In contrast, postsynthetic treatments occur after the synthesis of electrodes. Recently, such postsynthetic treatments based upon illumination, chemistry, electrochemistry, or combinations thereof have led to dramatic improvements in the performance and efficiency of BiVO₄ photoanodes. This Perspective summarizes recent BiVO₄ postsynthetic treatments with mechanistic details and highlights important future directions. One broad challenge is that multiple interpretations of defect changes may be consistent with routine X-ray photoelectron spectroscopy data. Further experiments are suggested to better differentiate between the proposed defect changes. Also, performance changes are considered separately with respect to charge separation and charge injection efficiencies as well as within the context of known synthetic modifications. The emergence of postsynthetic treatments highlights new opportunities to understand and improve photoelectrodes. Similar mechanisms may be of further utility as researchers turn more focus toward the development of novel multinary metal oxide photoabsorbers for the production of solar fuels. Lastly, postsynthetic treatments also elucidate possible electrode changes under extended service and can provide new strategies to enable extended device performance.