Free-standing BiOI@MWCNTs photoelectrodes for photo-rechargeable zinc-ion batteries

Photo-rechargeable batteries can implement solar energy harvesting and storage simultaneously and have attracted strong interest from researchers. The development of photoactive electrodes is the key to promoting the development of high-performance photocells. Herein, a free-standing BiOI@MWCNTs film is developed as photoelectrode to achieve the effective separation of photogenerated electron-hole pairs for high-efficiency solar-electric-chemical energy conversion. Light can charge up photocells with a photoconversion efficiency of ∼1.3%, as well as accelerate charge transfer without requiring any external bias voltage. Ex situ XRD and XPS tests prove that the enhanced electrochemical reaction kinetics can improve the chemical-electric energy conversion efficiency under illumination. The capacity of the proposed photocell can be increased by 10.6% (from 195 mA h g−1 to 216 mA h g−1 at 0.2 A g−1) and 57.9% (from 76 mA h g−1 to 120 mA h g−1 at 5.0 A g−1) in light condition, while exhibiting a cyclic life of up to 600 cycles. This work can help to deepen the understanding of photo-rechargeable batteries.