Enhanced photoelectrochemical water splitting using a cobalt-sulfide-decorated BiVO4 photoanode

Solar-driven water splitting is considered as a promising method to mitigate the energy crisis and various environmental issues. Bismuth vanadate (BiVO4) is photoanode material with tremendous potential for photoelectrochemical (PEC) water splitting. However, its PEC performance is severely hindered owing to poor surface charge transfer, surface recombination at the photoanode/electrolyte junction, and sluggish oxygen evolution reaction (OER) kinetics. In this regard, a novel solution was developed in this study to address these issues by decorating the surface of BiVO4 with cobalt sulfide, whose attractive features such as low cost, high conductivity, and rapid charge-transfer ability assisted in improving the PEC activity of the BiVO4 photoanode. The fabricated photoanode exhibited a significantly enhanced photocurrent density of 3.2 mA cm−2 under illumination at 1.23 V vs. a reversible hydrogen electrode, which is more than 2.5 times greater than that of pristine BiVO4. Moreover, the CoS/BiVO4 photoanode also exhibited considerable improvements in the charge injection yield (75.8% vs. 36.7% for the bare BiVO4 film) and charge separation efficiency (79.8% vs. 66.8% for the pristine BiVO4 film). These dramatic enhancements were primarily ascribed to rapid charge-transport kinetics and efficient reduction of the anodic overpotential for oxygen evolution enabled by the surface modification of BiVO4 by CoS. This study provides valuable suggestions for designing efficient photocatalysts via surface modification to improve the PEC performance.