Photo-driven Oxygen Vacancies Extends Charge Carrier Lifetime for Efficient Solar Water Splitting.

Excessive surface oxygen vacancies would decrease the charge carrier lifetime and cause the serious recombination at the semiconductor/electrolyte interface. In this context, a"photocharge/discharge"strategy exposure to AM 1.5G sunlight is proposed to initiate the WO 3 photoelectrode and suppress the main charge recombination, which remarkably improves the photoelectrochemical (PEC) perormance. The photocharged WO 3 surrounded by a 8-10 nm overlayer and oxygen vacancies could be operated more than 25 cycles with 50 h durability without significant decay on PEC activity. Further heterojuncted with the CuO, the photocharged WO 3 /CuO photpanode exhibits an outstanding photocurrent of 3.2 mA cm -2 at 1.23 V RHE with a low onset potential of 0.6 V RHE , which is one of the best performance of p-n heterojunction structure. Importantly, using the nonadiabatic molecular dynamics combined with time-domain density functional theory, we clarify the prolonged charge carrier lifetime of photocharged WO 3 , as well as how electronic systems of photocharged WO 3 /CuO semiconductors enable the effective photoinduced electrons transfer from WO 3 into CuO. This work provides a feasible route to address excessive defects existed  in photoelectrodes whilst without causing the extra recombination, further enhancing the carrier lifetime and boosting PEC water oxidation.