LAUSR

Abstract Water oxidation with multielectron transfer is regarded as the crucial step in photocatalytic water splitting. However, a facile but efficient method to promote its slow kinetics is still highly demanding. This work demonstrates that Cl- surface modification drastically enhances photocatalytic water oxidation over BiVO4 as well as WO3. The optimal modified BiVO4 achieves a photocatalytic activity of 4.2 orders enhancement relative to the pristine BiVO4, giving up to an excellent apparent quantum efficiency of 34.6% at 420 nm. Cl--modified 30-facet BiVO4 with 2.6 times enhancement confirms that the surface reaction involved with photogenerated holes can be dramatically accelerated by Cl- modification in addition to enhanced charge carrier separation. Our results highlight the impact of Cl- modification on the reaction kinetics and pathway during the photocatalytic water oxidation process, which has been mostly overlooked. Systematic studies (DFT simulations, kinetic experiments) reveal that Cl- modification remarkably reduces the photocatalytic water oxidation energy barrier and alters reaction pathway, which is also manifested in facilitated H2O molecule activation in synchronous illumination XPS (SI-XPS) study. The EXAFS and angle-resolved XPS (AR-XPS) results show that Cl bonds to Bi and mainly concentrates on the surface of modified BiVO4. Our findings provide an effective and facile approach to exploring efficient O2 evolution semiconductors for photocatalytic water splitting.