Plasmonic RuO2 Coupled with Work Function-Tuned Cu(OH)2 as Cathodes for Enhanced Visible Light-Responsive Zn-Air Batteries

Abstract

Photo-assisted Zn-air batteries (ZABs) can enhance the kinetics of oxygen reduction and oxygen evolution reactions (ORR/OER); however, issues like rapid charge carrier recombination and limited output voltage persist. Herein, a sandwich-structured photo-assisted ZABs is constructed, in which RuO₂ is respectively coupled with a hole transport layer (HTL) (RuO₂-HTL) and an electron transport layer (ETL) (RuO₂-ETL) as the cathodes, with Zn serving as the anode in the middle. Specifically, HTL and ETL are achieved by interfacial dipoles modulating the work function of Cu(OH)₂, whereas photogenerated electrons and holes are originated from the plasmonic effect of RuO₂. In the photo-assisted discharge process, the plasmonic-excited holes are pumped by HTL to neutralize the electrons from the Zn anode side, thereby enhancing charge separation. The retained electrons in RuO₂ facilitate the ORR process. On the contrary, ETL pumps the plasmon-excited electrons to participate in the reduction of ZnO at the anode, while the holes retained by the extracted RuO₂ accelerate the OER. This approach breaks the overpotential barrier in RuO₂-based ZABs, achieving a record-high discharge voltage of 1.80 V and an unprecedented low charge voltage of 0.83 V. This novel cathode structure design provides an untapped pathway to obtain the high-performance photo-assisted batteries.