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

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 mu mol of hydrogen. Furthermore, this catalyst demonstrates a strong ability to catalytically reform microplastics, the hybrid system simultaneously generates 331 mu mol 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.