Bifacial Modulation of Carrier Transport in BiVO4 Photoanode for Stable Photoelectrochemical Water Splitting via Interface Engineering

Abstract Monoclinic bismuth vanadate photoanodes promise high efficiency‐to‐cost ratios for photoelectrochemical (PEC) water splitting owing to their suitable band structure and ease of synthesis. However, inadequate charge separation and sluggish oxidation kinetics remain a fundamental challenge. This study investigates bifacially interface engineered BiVO 4 photoanodes by considering a seed‐layer and NiOOH oxygen evolution catalyst (OEC) over‐layer to regulate the charge carrier transport and improve the overall PEC water‐splitting performance. The modification of the BiVO 4 /FTO interface stimulates electron flow towards fluorine‐doped tin oxide (FTO) and a NiOOH over‐layer improves the facile hole transfer from BiVO 4 to the electrolyte. Compared to the moderate photocurrent density of a bare BiVO 4 photoanode (1.5 mA cm −2 ), the interface‐engineered Seed_BiVO 4 _NiOOH photoanode shows a remarkably high (≈3.4 times higher) photocurrent density of 5.10 mA cm −2 at 1.23 V vs reversible hydrogen electrode with impressive long‐term stability over 9 h under illumination. The optimally interface engineered Seed_BiVO 4 _NiOOH photoanode shows an excellent photoconversion efficiency (1.83%), with significant improvement in bulk charge separation efficiency. This work presents a promising strategy for the development of a highly stable PEC water‐splitting device and eliminates the intrinsic material shortcomings of the bare BiVO 4 photoanode by modulating the carrier transport via bifacial interface engineering.