Unassisted Switchable Dual‐Photoelectrode Devices Utilizing p‐n Carbon Quantum Dots as “Semiconductor Electrolytes”: Optimization Between H <sub>2</sub> O <sub>2</sub> and Solar Electricity Production
Huimin Duan, Chenguang Li, Liu‐Meng Mo, Jingshuang Dang, Xiaohui Jia, Jiacheng Yu, Yu‐Hang Mei, Anders Thapper, Hongyan Wang
Abstract
Abstract Switchable self‐driven photoelectrochemical (PEC) devices are developed to boost H 2 O 2 or electricity generation under visible‐light illumination, in which p‐n type carbon quantum dots (N‐CQDs) is applied as conceptually‐new “semiconductor electrolytes”. The N‐CQDs contains N‐dopants, and both negatively‐ and positively‐charged surface groups. This allows N‐CQDs to act as the electrolyte and to interact with both a BiVO 4 photoanode and a Cu 2 O photocathode. In a two‐compartment cell with a separating membrane, N‐CQDs can dynamically form p‐n heterojunctions with the photoanode or the photocathode, facilitating charge separation. In this setup, the fine‐tuned electronic structure of N‐CQDs promotes the two‐electron reactions with water or O 2 to produce H 2 O 2 , achieving a rate of 28 µ m min −1 and Faradic efficiency exceeding 80%. Switching into a one‐compartment cell, N‐CQDs promotes four‐electron charge transfer and stabilizes the photoelectrodes, giving electricity output for over 120 h. This control over electron transfer, selectivity, and durability cannot be achieved using traditional electrolytes.