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Novel p-n heterojunction of Bi2Sn2O7-Ag2CrO4 photocatalysts with various contents of Bi2Sn2O7 were in-situ synthesized at 25 °C. X-ray diffraction, transmission electron microscopy, UV–vis diffuse reflectance spectra, photoluminescence emission and electrochemical impedance spectra were employed to characterize the as-prepared samples. Experimental results showed that, under the visible light irradiation, with increasing the amount of Bi2Sn2O7, the degradation efficiency of the as-prepared hybrids was first increased and then decreased. It possessed the highest degradation efficiency of 97.5 % for rhodamine B in 120 min, which was obviously higher than that of 76.7 % of Ag2CrO4 and 11.8 % of Bi2Sn2O7, respectively. Moreover, it possessed the degradation efficiency of 90.4 % for methyl orange and 99.8 % for methylene blue. In addition, after it was circulated for 5 times, the as-prepared hybrids still possessed the degradation efficiency of 90.2 % for rhodamine B, which increased by 240.4 and 1950.0 % in comparison with Ag2CrO4 and Bi2Sn2O7, respectively. The enhanced photocatalytic activity could be attributed to the formation of the p-n heterojunction at the interface of p-Bi2Sn2O7 and n-Ag2CrO4.

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.