Efficient bismuth vanadate homojunction with zinc and tungsten doping via simple successive spin-coating process for photoelectrochemical catalyzing water oxidation

BiVO₄ is one of the promising photocatalysts for water oxidation due to its suitable band positions and narrow band gap. Doping heteroatoms in BiVO₄ can increase charge concentration and develop efficient charge-transfer path via shifting conduction or valance band edges. Spin-coating method is simple and cost-effective for depositing photocatalyst on conductive substrate. It is the first time to use the simple spin-coating method for fabricating multi-layered Zn-doped and W-doped BiVO₄ homojunction as photocatalyst for water oxidation. The pristine BiVO₄ and single metal-doped BiVO₄ electrodes are also fabricated for comparison. The charge concentration is enhanced by doping tungsten in BiVO₄. The preferable type II homojunction electrode composed of Zn-doped BiVO₄ bottom layer and W-doped BiVO₄ top layer (W:BVO/Zn:BVO) shows the highest photocurrent density of 2.85 mA/cm² at 1.23 V_RHE under air mass 1.5 global and the smallest charge-transfer resistance of 238.34 Ω. The pristine BiVO₄ electrode only shows a photocurrent density of 1.88 mA/cm² measured at the same condition. The excellent long-term stability with the photocurrent retention of 100% under continuous light illumination for 4000 s is also achieved for the optimized W:BVO/Zn:BVO electrode. This work provides a simple way to attain highly improved electrochemical performance for BiVO₄ toward photoelectrochemical catalysis.