Rational Design of CdS QDs/CeO2 Nanocube S-Scheme Heterojunctions for Highly Efficient C2H4 Scavenging in Fresh Produce Preservation

Effectively eliminating ethylene (C2H4) during postharvest phase and distribution of fruits and vegetables continues to pose a significant technical hurdle. Although S-scheme heterojunctions have shown promise in optimizing charge carrier separation and redox capacity for ethylene degradation, their catalytic efficiency is still limited by insufficient oxygen activation kinetics. Herein, a novel S-scheme heterojunction composed of CdS quantum dots and CeO2 nanocubes was first rationally designed and was innovatively constructed for the first time, leveraging the oxygen-affinitive characteristics of CeO2 and guided by DFT calculations to enhance interfacial charge transfer and oxygen activation. The optimized 10-CdS–CeO2 composite exhibited superior photocatalytic activity under visible light exposure, exhibited a quasi-first-order reaction rate reaching 1.72 min−1, 35 and 297 times higher than CdS and CeO2, respectively. Even under low-intensity illumination (50 mW·cm−2), complete ethylene degradation was observed within 4 min, surpassing all previous literature known to the authors. Mechanistic investigations via in situ irradiated XPS, UPS, PL, TRPL, and ESR confirmed strong interfacial interactions, efficient S-scheme charge separation, and accelerated O2 activation. The findings establish a reliable theoretical and experimental basis for guiding the development of next-generation high-performance photocatalysts for ethylene scavenging, providing a promising strategy for postharvest preservation of fruits and vegetables.