Promoting photon-generated carrier separation via a type-II Cu₂O@MOF heterojunction cathode for photo-rechargeable...

Photo-rechargeable zinc-ion batteries (PR-ZIBs) represent an emerging renewable energy technology that offers a compact and efficient paradigm for direct solar energy conversion and storage. However, the development of high-performance photocathodes is hindered by challenges such as severe charge recombination and low photoelectric conversion efficiency. Herein, a photocathode composed of a Cu₂O@Cu₃(BTC)₂ heterojunction on carbon cloth (CC) was constructed via a surfactant-free topological transformation strategy. Benefiting from the structural design, the close interface contact and ideal II-type band alignment within the heterojunction provide an advantageous pathway for the effective interfacial charge separation. Consequently, this not only accelerates electron transfer at the cathode to facilitate the photo-oxidation reaction during charging but also reduces the charge transfer resistance and Zn²⁺ migration barrier, thereby promoting Zn²⁺ intercalation during discharge. The optimized Cu₂O@Cu₃(BTC)₂/CC photocathode delivers a 53.6% higher discharge capacity under illumination at 0.1 A g^-1 compared to that in the dark. Furthermore, it enables PR-ZIBs to achieve self-sustained photo-charging without an external power source. The open-circuit voltage rapidly increases from 0.4 V to 0.94 V within 1 h under illumination, yielding a photoelectric conversion efficiency of 0.79%. This work demonstrates an effective strategy of constructing MOF-semiconductor heterostructures to advance photo-rechargeable battery technology for sustainable energy storage.