Oxygen vacancies and p-n heterojunction modified BiOBr for enhancing donor density and separation efficiency under visible-light irradiation

It remains a great challenge to overcome the problems of poor conductivity and rapid charge recombination in bismuth oxybromide (BiOBr). Herein, for the first time we report the synergistic effect of oxygen vacancies (Ov) and p-n heterojunction to improve photoelectrochemical performance of BiOBr. Benefitting from the new electron donor level caused by oxygen vacancies, the visible-light absorption region, carrier concentration and exposure of {001} facets of BiOBr are all increased. In the meantime, the 2D p-n heterojunction between BiOBr and BiOI leads to a built-in electric field and thus significantly accelerating the charge separation and transfer. Upon visible light irradiation, the resulted BiOBr-Ov/BiOI photoanode presents robust photoelectrochemical performance, achieving a photocurrent density of 1.33 mA/cm2 at 1.23 V vs. RHE. This work not only provides new insight for designing efficient photoelectrodes but also highlights the importance of oxygen defect-engineering strategy in photoelectrochemical water splitting.