Vacancy pair induced surface chemistry reconstruction of Cs2AgBiBr6/ Bi2WO6 heterojunction to enhance photocatalytic CO2 reduction

Cs 2 AgBiBr 6 /Bi-O vacancy pair Bi 2 WO 6 (Cs 2 AgBiBr 6 /V Bi-O Bi 2 WO 6 ) heterojunction was synthesised for photocatalytic CO 2 reduction under visible light irradiation. The characterisation results show that the Bi -O vacancy pairs can reconstruct the surface electronic states of the heterojunction. The optimal 10%Cs 2 AgBiBr 6 /V Bi- O Bi 2 WO 6 heterojunction exhibited a substantial CO yield of 48.5 mu mol/g, approximately 22 times higher than that of Bi 2 WO 6 , exceeding the performance of most of the Bi-based photocatalysts reported to date. The enhanced activity of 10%Cs 2 AgBiBr 6 /V Bi-O Bi 2 WO 6 was due to exposed Bi sites that facilitate the chemisorption and activation of CO 2 and the lower reaction energy barrier for the protonation of CO 2 to CO via the formation of COOH* intermediates with the cooperation of surface four-coordinated H 2 O molecules. Furthermore, charge migration from Cs 2 AgBiBr 6 to V Bi-O Bi 2 WO 6 and space-charge distribution in the heterojunction under visible light irradiation were demonstrated. This work reveals defective heterojunction catalysts that facilitate the transformation of reactive molecules in surface/interfacial reactions.