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

Abstract

Solar-driven water splitting is considered as a promising method to mitigate the energy crisis and various environmental issues. Bismuth vanadate (BiVO 4 ) 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 BiVO 4 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 BiVO 4 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 BiVO 4 . Moreover, the CoS/BiVO 4 photoanode also exhibited considerable improvements in the charge injection yield (75.8% vs . 36.7% for the bare BiVO 4 film) and charge separation efficiency (79.8% vs . 66.8% for the pristine BiVO 4 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 BiVO 4 by CoS. This study provides valuable suggestions for designing efficient photocatalysts via surface modification to improve the PEC performance. An excellent CoS/BiVO 4 photoanode was prepared by decorating CoS onto the surface of BiVO 4 . The resulting CoS/BiVO 4 photoanode exhibited a significantly enhanced photocurrent density with considerably enhanced charge injection and separation efficiencies compared to those of pure BiVO 4 . This study provides valuable instructions for surface-modification-based design and decoration of photoanodes for efficient photoelectrochemical water splitting.