Cooperative catalytic behavior of CoS and Bi₂S₃ nanoparticles on Zr:BiVO₄ photoanodes for enhanced photoelectrochemical sulfite oxidation coupled with pharmaceutical pollution degradation

Photoelectrocatalysis is a promising advancing technology that converts energy into electricity and purifies the environment. A photoelectrochemical (PEC) reaction that splits water and degrades pharmaceutical pollutants can be achieved using bismuth vanadate (BiVO₄). The water oxidation dynamics of BiVO₄ photoanodes are sluggish owing to poor charge separation. In this paper, we demonstrate that bismuth sulfide (Bi₂S₃) and cobalt sulfide (CoS) nanoparticles have a cooperative effect on Zr-doped BiVO₄ electrodes (Zr:BiVO₄) fabricated via PEC techniques. PEC water splitting results reveal that optimal Zr:BiVO₄@Bi₂S₃-CoS films have a photocurrent response of 3.09 mA cm⁻² at 1.23 V vs. the RHE, which is three times better than Zr:BiVO₄ films. As a result of combining the above features, Zr:BiVO₄@Bi₂S₃/CoS electrodes achieved 1.53% applied bias photon-to-current efficiency (ABPE), with a substantial reduction in photocurrent onset potential. Additionally, the composite photoanode demonstrated superior performance in the PEC degradation of tetracycline hydrochloride (TCH) to previously reported photonanodes. In the PEC reaction, Zr:BiVO₄@Bi₂S₃/CoS yielded the most efficient degradation of TCH (94%), which was six times more than Zr:BiVO₄ and EC (55%). The present study presents a visible light-responsive, efficient, sustainable water-splitting technique for producing hydrogen and provides new insights into wastewater treatment.