Z-scheme heterojunction engineering and hole-extraction layer enable efficient photoelectrochemical water splitting on BiVO4 photoanode

Abstract

This study presents a novel Z-scheme heterostructure that was developed by integrating three-dimensional CoFe2O4 nanospheres with Mo and W co-doped BiVO4 (MW:BVO). Subsequently, ultra-thin hydroxides (NiOOH-FeOOH) were grown on the surface of the MW:BVO@CFO photoanode in the presence of tannic acid (TA), resulting in the formation of MW:BVO@CFO/TANF photoanodes. Notably, TANF served as a hole extraction layer. Compared to pristine MW:BVO, the photocurrent density of MW:BVO@CFO/TANF photoanodes exhibited a significant enhancement from 0.96 mA/cm2 to 6.03 mA/cm2 at 1.23 VRHE with a charge separation efficiency of 90.2 % due to the synergistic effect of the Z-scheme structure and hole extraction layer. Notably, the Z-scheme architecture facilitates the effective separation and transfer of electron-hole pairs, thereby retaining electrons and holes with high redox capacity. Meanwhile, the hole extraction layer quickly exports and aggregates the photo-generated holes, thereby further improving the separation efficiency of electron-hole pairs.