An Electron Transfer Mediated Mechanism for Efficient Photoreforming of Waste Plastics Using a Ni₃S₄/ZnCdS Heterojunction

Abstract

The oxidative degradation of plastics in conjunction with the production of clean hydrogen (H₂) represents a significant challenge. Herein, a Ni₃S₄/ZnCdS heterojunction is rationally synthesized and employed for the efficient production of H₂ and high-selectivity value-added chemicals from waste plastic. By integrating spectroscopic analysis techniques with density functional theory (DFT) calculations, a solely electron transfer-mediated reaction mechanism is confirmed, wherein Ni₃S₄ extracts electrons from ZnCdS (ZCS) to promote the spatial segregation of photogenerated electrons and holes, which not only facilitates H₂ production but also maintains the high oxidation potential of holes on the ZCS surface, favoring hole-dominated plastic oxidation. Notably, the catalyst exhibited efficient H₂ production rates as high as 27.9 and 17.4 mmol g^-1 h^-1, along with a selectivity of 94.2% and 78.3% in the liquid product toward pyruvate and acetate production from polylactic acid (PLA) and polyethylene terephthalate (PET), respectively. Additionally, carbon yields of 26.5% for pyruvate and 2.2% for acetate are measured after 9 h of photoreforming, representing the highest values reported to date. Overall, this research presents a promising approach for converting plastic waste into H₂ fuel and high-selectivity valuable chemical products, offering a potential solution to the growing issue of "White Pollution".