Can a PbCrO4 Photoanode Perform as Well as Isoelectronic BiVO4?

Oxide-based photoelectrodes recently have been at the forefront of research for photoelectrochemical water splitting. While most oxide-based photoanodes suffer from severe electron-hole recombination, BiVO4 photoanodes are known to achieve exceptionally high electron-hole separation efficiencies. However, an understanding of what features of BiVO4 lead to this desired property is currently lacking. In this study, we sought to elucidate these features by investigating PbCrO4, which has electronic and structural similarities to BiVO4. For this goal, we prepared PbCrO4 as a high-quality photoanode and compared its photoelectrochemical properties and stability with those of BiVO4. Our results showed that the electron-hole separation efficiency for PbCrO4 at 1.23 V vs the reversible hydrogen electrode (RHE) was similar to 67%, which is considerably higher than most oxide photoanodes and approaches that of state-of-the-art BiVO4. The photoelectrochemical similarities and differences between PbCrO4 and BiVO4 were discussed in detail, and the origins for their similarities and differences were investigated via combined experimental and computational studies, which include the computation of electronic band structures, band edge alignments, and the formation energies of oxygen vacancies of PbCrO4 and BiVO4. The shared electronic and structural features of PbCrO4 and BiVO4 elucidated in this study provide useful guidelines to develop high-performance oxide-based photoanodes.