Oxygen vacancy engineering of WO3 toward largely enhanced photoelectrochemical water splitting

Photoelectrochemical (PEC) water splitting plays a crucial role in clean and renewable energy production, in which solar-to-chemical energy conversion efficiency is definitively dependent on the charge carrier generation and transfer ability. Here we report a facile and effective method to largely enhance the transfer ability of charge carriers via fabrication of an oxygen vacancy-rich WOx modulated WO3 photoanode (WO3-OV). Experimental studies show that the oxygen vacancies significantly increase the charge carrier density of WO3-OV (similar to 6.89 times larger than that of pristine WO3). Moreover, density functional theory calculations reveal that a WO3/WOx heterojunction is formed due to the energy difference between WO3 and oxygen vacancy-rich layer, which improves the build-in electronic field and reduces the charge recombination. As a result, the WO3-OV photoanode gives largely improved charge separation efficiency (67.2%) and a high photocurrent density of 1.35 mA cm(-2) at 1.23 V vs. RHE, among the highest level in WO3-based materials. It is expected that the surface modulation by oxygen vacancy can be extended to other semiconductor systems for advanced performance in the fields of energy conversion and storage. (c) 2018 Published by Elsevier Ltd.