A Sequential Doping Strategy for Architecturally Controlled BiVO4 Photoanodes with Synergistic Co-Doping Enabled by BiOI Conversion for Water Splitting

Abstract

The fabrication of nanoporous bismuth vanadate (BiVO4) photoanode via bismuth oxyiodide (BiOI) template conversion represents a crucial approach for obtaining a high-quality, binder-free, and crack-free film with ideal morphology. However, this route is incompatible with conventional doping methods, resulting in BiVO₄ in its pristine state, where poor bulk charge transport severely limits performance. Herein, we introduce a novel, controlled, quantitative, precursor-state, sequential doping strategy to effectively co-dope this superior architecture with Barium (Ba) and Niobium (Nb) for the first time. The synergetic approach successfully resolves the bulk electronic limitation, yielding a charge separation efficiency of more than 95%. The optimized Nb/Ba co-doped BiVO4 photoanode decorated with nickel iron oxide (NiFeOx) co-catalyst exhibits a remarkable photocurrent density of 6.2 mA/cm2 at 1.23 V vs. RHE, a 4-fold increase compared to its original counterpart. This work represents a significant achievement in overcoming the traditional limitations of BiOI-templated BiVO4 photoanodes and sets a new standard for the rational design of high-performance solar fuel devices.