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High photoinduced charge recombination process and indolent water oxidation kinetics are major drawbacks of the bismuth vanadate (BiVO4) photoanode in photoelectrocatalytic (PEC) water splitting. To address these issues, a bismuth vanadate/copper oxide (BiVO4/CuO) p–n junction electrode was fabricated via the electrodeposition method, and its PEC performance was studied using 0.1 M potassium phosphate (KPi) as an electrolyte under AM 1.5G (100 mW cm–2) irradiation. At an optimized condition, the BiVO4/CuO p–n junction electrode showed improvement in the current density of 2.05 mA cm–2 at +1.23 VRHE, which was ∼2-fold higher than the BiVO4 electrode (0.99 mA cm–2). The applied bias photon-to-current efficiency (ABPE) of the BiVO4/CuO electrode was also ∼2.5-fold higher than the BiVO4 electrode. Loading of CuO over the BiVO4 surface improved the light absorption ability of the electrode in the entire UV–vis region, leading to generation of a greater number of photoinduced charge carriers, and it also enhanced the reactive sites for water oxidation as per the calculation of double-layer capacitance (Cdl). The formation of inner electric field (IEF) at the interface between BiVO4 and CuO offered well-separated electron–hole pairs in association with improvement in the lifetime of charge carriers, and as a consequence, the BiVO4/CuO electrode showed a transient decay time of 4.45 s, which was ∼1.6-fold higher than the BiVO4 electrode (2.81 s). The formation of p–n junction between BiVO4 and CuO significantly reduced the charge transfer resistance (Rct) at the electrode/electrolyte interface (EEI), and as a result, the BiVO4 and BiVO4/CuO electrodes show Rct values of 454.4 and 201.9 Ω, respectively, under light illumination. Moreover, the Bode phase analysis confirmed quick hole consumption in the presence of the BiVO4/CuO electrode over the pristine BiVO4 electrode during water oxidation process. Overall, the formation of a p–n junction facilitated well-separated electron–hole pairs and improved the hole transfer at the EEI for an efficient PEC water oxidation process.
Murugan et al. (Mon,) studied this question.