Rational Design of <scp>C</scp> d <scp>S QD</scp> s/ <scp>C</scp> e <scp>O</scp> ₂ Nanocube S‐Scheme Heterojunctions for Highly Efficient <scp>C</scp> ₂ <scp>H</scp> ₄ Scavenging in Fresh Produce Preservation

Effectively eliminating ethylene (C 2 H 4 ) 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 CeO 2 nanocubes was first rationally designed and was innovatively constructed for the first time, leveraging the oxygen‐affinitive characteristics of CeO 2 and guided by DFT calculations to enhance interfacial charge transfer and oxygen activation. The optimized 10‐CdS–CeO 2 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 CeO 2 , 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 O 2 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.