Boosting Charge Transport in BiVO4 Photoanode for Solar Water Oxidation

The ability to regulate charge separation is pivotal for obtaining high efficiency of any photoelectrode used for solar fuel production. Vacancy engineering for metal oxide semiconductor photoelectrode is a major strategy but has faced a formidable challenge in bulk charge transport because of the elusive charge self-trapping site. In this work, a new deep eutectic solvent to engineer bismuth vacancies (Bi-vac) of BiVO4 photoanode is reported; the novel Bi-vac can remarkably increase the charge diffusion coefficient by 5.8 times (from 1.82 x 10(-7) to 1.06 x 10(-6) cm(2) s(-1)), which boosts the charge transport efficiency. Through further loading CoBi cocatalyst to enhance charge transfer efficiency, the photocurrent density of BiVO4 photoanode with optimal Bi-vac concentration reaches 4.5 mA cm(-2) at 1.23 V vs reversible hydrogen electrode under AM 1.5 G illumination, which is higher than that of previously reported O-vac engineered BiVO4 photoanode where the BiVO4 photoanode is synthesized by a similar procedure. This work perfects a cation defect engineering that enables the potential capability to equate the charge transport properties in different types of semiconductor materials for solar fuel conversion.