Interfacial Charge Asymmetry in Ni-Doped CdZnS/MnWO4 S-Scheme Heterojunction Drives Photoreforming of Microplastics to Hydrogen and Pyruvic Acid

Abstract Solar-driven photocatalytic water splitting represents a promising route for sustainable hydrogen production. However, the practical application of single-component photocatalysts is severely constrained by rapid bulk charge-carrier recombination. CdZnS (CZS) solid solutions have garnered significant interest as visible-light-active photocatalysts due to their compositionally tunable band structures. However, photocorrosion and sluggish interfacial charge transfer critically hinder their practical application. To address these limitations, we herein report an S-scheme heterojunction photocatalyst (Ni-CZS/MW), constructed by integrating Ni-doped CZS (Ni-CZS) with MnWO4 (MW). Ni-doping markedly diminishes the work function of Ni-CZS, creating a substantial work-function difference with MW that induces interfacial charge asymmetry. An internal electric field generated by the intimate contact at the Ni-CZS/MW interface directs the migration of photoexcited electrons from MW to Ni-CZS through an S-scheme charge-transfer pathway, thereby significantly enhancing charge-carrier separation efficiency. Under visible-light irradiation, the optimized Ni-CZS/MW heterostructure produces 882 μmol of hydrogen. Furthermore, this catalyst demonstrates a strong ability to catalytically reform microplastics, the hybrid system simultaneously generates 331 μmol of hydrogen and upcycles PLA into pyruvic acid (PA). Collectively, these findings elucidate the synergistic roles of S-scheme heterojunction engineering and Ni-doping in modulating charge-carrier dynamics, and provide a strategic framework for designing photocatalysts tailored for plastic waste valorization.