Scalable ambient conditions-based fabrication of flower-like bismuth vanadate (BiVO₄) film incorporating defects aimed at visible-light-induced water-splitting application

The scalable application of bismuth vanadate (BiVO₄) in photoelectrochemical water splitting is restricted by its low charge separation efficiency and slow water oxidation kinetics. Here, modified BiVO₄ photoanodes were fabricated at ambient conditions with polyethylene glycol (PEG) and potassium hydroxide (KOH) for improving the electron-hole generation rate and lowering the charge carrier recombination rate. Modification by PEG produced 3D flower-like BiVO₄ microspheres, along with Bi⁵⁺, Bi^(3−x)+, and V⁴⁺ species onto the PEG-BiVO₄ surface, which were accompanied by oxygen vacancies (OVs) working in tandem with these species and acting as surface-active intermediates, thereby facilitating hole transfer to the electrolyte. Under visible light irradiation (100 mW/cm²), 3D flower-like PEG-BiVO₄ microspheres produce the maximum photocurrent density of 5.75 mA/cm² in water splitting at 1.23 V against a reverse hydrogen electrode (RHE). The superior photoelectrochemical performance of PEG-BiVO₄ over its counterparts is attributed to the incorporation of 3D flower-like microspheres and band structure modulation by the O vacancies, Bi^(3−x)+, Bi⁵⁺, and V⁴⁺ species. The synthesized PEG-BiVO₄ is expected to attract attention as a scalable photocatalyst for oxidation of water because it is easy to synthesize at room temperature and it exhibits superb photocatalytic performance.