Copper vacancies-driven tensile lattice strain accelerates oxygen reduction in photo-assisted Zn-air batteries cathodes

Abstract

Recently, photo-assisted Zn-air batteries (ZABs) have been confirmed to accelerate the kinetics of oxygen reduction reaction (ORR); however, challenges such as rapid charge carrier recombination and low light utilization efficiency still remain. Herein, lattice-distorted copper oxide was constructed by copper vacancies (CuO-0.9%V_Cu). Approximate 0.9% deficiency of Cu²⁺ (t_2g⁶e_g³) creats 2.16% tensile strain through the Jahn-Teller effect. This tensile strain allows strong chemisorption and activation of *OOH intermediates on active Cu atoms due to the upshift of d-band center, thus prompting fast O₂ reduction rate. Additionally, copper vacancies can act as hole traps to inhibit rapid electron-hole recombination, enabling the CuO-0.9%V_Cu photocathode to achieve a charge separation yield of 59% and a transfer yield of 70% in ORR reactions. Therefore, ZABs using CuO-0.9%V_Cu as photocathodes deliver a remarkable discharge voltage of 1.36 V, a high energy efficiency of 70.47%, and a cyclic durability of surpassing 100 h under 1-sun illumination. CuO-0.9%V_Cu provides a typical case for the usage of clean and readily available light energy, as well as offers a typical case to realize simultaneously harvesting, converting and storing of solar energy.