Nitrogen-doped cobalt-iron oxide cocatalyst boosting photoelectrochemical water splitting of BiVO4 photoanodes

Photoelectrochemical water splitting using bismuth vanadate (BiVO4) photoanodes is of special interest for solar energy utilization. However, its solar-to-hydrogen conversion efficiency is hindered by unfavorable surface reaction kinetics, which requires the development of efficient cocatalysts. Here, a nitrogen-doped cobalt-iron oxide (N-CFO) cocatalyst layer is designed on the BiVO4 (BVO) by using Prussian blue analogue (PBA) precursor. The N-CFO/BVO photoanode exhibits an improved photocurrent density of 4.83 mA/cm2 at 1.23 V vs. reversible hydrogen electrode under AM 1.5 G illumination, which is 4.13-fold that of pure BVO photoanode and surpasses that of CFO/BVO with oxygen vacancies. Mechanism studies reveal that compared with oxygen vacancies, nitrogen dopants greatly enhance electrical conductivity and boost reaction activity of cobalt-iron oxide. Owing to the diverse composition of PBAs, this work provides a novel insight into the effects of nitrogen dopants, as well as a general strategy to design efficient and cheap cocatalysts for photoanodes.