Fe−N Co‐Doped BiVO₄ Photoanode with Record Photocurrent for Water Oxidation

Abstract

Bismuth vanadate ranks among the most promising photoanodes for photoelectrochemical water splitting. Nonetheless, slow charge separation and transport are key barriers to its photoefficiency. Here, we present a co‐doping strategy that significantly improves the charge separation performance of BVO. Under standard one sun illumination, the Fe‐N co‐doped BVO photoanode (Fe‐N‐BVO) by N‐coordinated Fe precursor reaches a record photocurrent density of 7.01 mA cm‐2 at 1.23 V vs RHE after modified a surface co‐catalyst. By contrast, much lower photocurrent density is obtained for the N‐doped and Fe‐doped BVO with separated N and Fe precursors. The detailed characterizations show that the high activity of the Fe‐N‐BVO is attributed to the enhanced photo‐induced bulk charge separation and the accelerated surface water oxidation kinetics. XPS, EXAFS and DFT calculations clearly show that, instead of formation of deep trapping state in the individually doped BVO, the co‐doping of Fe‐N into BVO generates Fe‐based electronic states just below the bottom of conduction band and N‐derived states just above the top of valence band. Such modulations in electronic structure enable the efficient trap of the electrons and holes to enhance the separation of photo‐induced carriers, but hinder the charge recombination originated from the deep trapping sites.