Dual Heterojunction Photocathode Synergy: Enabling Efficient Solar‐Assisted Oxygen Reduction for Next‐Gen Zn‐Air Batteries

Abstract The oxygen reduction reaction (ORR), as a pivotal cathodic process in energy conversion devices, suffers from intrinsically sluggish kinetics, which severely limits device performance. Integrating solar energy through photoelectrochemical (PEC) systems presents a promising strategy to overcome this limitation by enhancing ORR kinetics. Herein, a novel non‐noble metal photocathode (CuO/WO 3 /pTTh) is developed with optimized band alignment via dual heterojunction engineering. The design effectively suppresses electron‐hole recombination, enhances photovoltage generation, and significantly improves electrode stability. Owing to efficient charge transfer and accumulation at the outer layer, the optimized system achieves an exceptional ORR onset potential of 1.05 V vs. RHE (reversible hydrogen electrode) and catalytic efficiency (∼100%) under minimal applied bias. When integrated into a Zn‐air battery, this photoelectrocatalytic configuration delivers a high open‐circuit voltage of 1.5 V, surpassing conventional electrocatalytic systems. Moreover, the CuO/WO 3 /pTTh photocathode enables a higher discharge voltage in the solar‐assist ing Zn‐air battery than most reported systems. This work not only demonstrates the potential of dual heterojunction engineering in CuO‐based photocathodes for solar‐enhancing ORR but also provides fundamental insights for designing next‐generation PEC devices and photo‐assisting energy storage technologies.