Addressing phase instability and charge recombination in pyrolysis-synthesized BiVO4 via DFT-guided Mo doping for enhanced performance

Abstract Preparation of transparent bismuth vanadate (BiVO4, BVO) photoanode via a scalable metal-organic decomposition (MOD) method has been long-term plagued by severe charge recombination and phase instability, preventing its application in solar-to-chemical energy conversion. Here, we employ density functional theory (DFT) calculations to screen dopants by evaluating their carrier transport properties and thermodynamic effects on phase stability. On the basis, Mo is identified and experimentally confirmed as a dual-role dopant that suppresses the formation of the inactive zircon-type tetragonal (z-t) while simultaneously enhancing charge-transport properties of BVO. Consequently, phase-pure monoclinic scheelite (m-s) Mo-doped BVO films prepared by the MOD method yield an optimized transparent photoanode (denoted 3Mo-BVO), exhibiting a remarkable charge separation efficiency of 96.2% at 1.23 V vs. reversible hydrogen electrode. Together with modification of NiFeOx cocatalyst, the 3Mo-BVO photoanode was used for assembly of a tandem device with a photovoltaic (PV) solar cell to achieve overall water splitting with a benchmarking solar-to-hydrogen (STH) efficiency of 4.7%.