Highly Efficient Recovery of H₂ from Industrial Waste by Sunlight-Driven Photoelectrocatalysis over a ZnS/Bi₂S₃/ZnO Photoelectrode

Hydrogen (H2) fuel production from hazardous contaminants is not only of economic importance but also of significance for the environment and health. Hydrogen production is exemplified in this work by using bismuth sulfide (Bi2S3) sandwiched in between zinc sulfide (ZnS) and zinc oxide (ZnO) as dual-heterojunction photoelectrode to photoelectrochemically extract H2 from sulfide- and sulfite-containing wastewater, which is emitted in enormous quantities from the petrochemical industries. The H2 evolution rate over the ZnS/Bi2S3/ZnO photoelectrode under solar illumination amounts to 112.8 μmol cm–2 h–1, of which the photocurrent density in the meantime reaches 10.7 mA cm–2, by far exceeding those reported for additional Bi2S3-based counterparts in the literature. Such superior performance is ascribed on one hand to the broadband sunlight-harvesting ability of Bi2S3 that gives rise to respectable photoexcited electron–hole pairs. These photogenerated charge carriers are subsequently rectified by the built-in electric field at the ZnS/Bi2S3 and Bi2S3/ZnO heterojunctions to flow in the opposite directions to well circumvent the recombination losses and, most importantly, in turn contribute substantially to the H2 evolution reaction.