Dramatic enhancement of photocurrent for BiVO4/TiO2 heterojunction photoanode with suitable band-match via in-situ band regulation using Ta

Abstract

Low efficiency separation of photogenerated electron-hole pairs in semiconductors are still the main bottlenecks to high photoelectrochemical (PEC) water splitting. In this work, a dramatic enhancement of photocurrent was performed for a BiVO4/TiO2 nanoporous groves (NGs) heterojunction photoanode via in-situ band regulation of TiO2 using Ta. A convenient band-match between BiVO4 and TiO2 was obtained. Electrochemical and spectroscopic measurements indicate that doping of Ta in TiO2 positively affects the shifts in the conduction band potential and increases the electron density via an alteration of the band alignment from type I to type II at the BiVO4/TiO2 NGs heterojunction. Combined with the benefit of a short carrier diffusion length in TiO2 NGs, which improves charge collection/transportation efficiency, a significant improvement in photocurrent density, up to 1.77 mA cm−2 at 1.23 V vs RHE under visible light illumination, was obtained in the BiVO4/TiO2 NGs heterojunction. This is an increase of more than 250% compared to that of pure BiVO4 (0.7 mA/cm2). Such an efficient energy band design and the integration of high-performance nanomaterial indicate the advantages of this technique for potential implementation in solar driven water splitting.