A2V2O7 (A = Co, Ni, Cu and Zn) for CO2 reduction under visible-light irradiation: Effects of A site replacement

Electronic structure and surface character are two important factors of materials for photocatalytic CO 2 reduction. Herein, the simultaneous regulation of electronic structure and surface basicity of pyrovanadate A 2 V 2 O 7 (A = Co, Ni, Cu, Zn) were realized by changing the A-site element. The density functional theory (DFT) results suggested that Ni 2 V 2 O 7 had the strongest crystal field and the greatest splitting of V 3d, resulting in the largest mobility of photogenerated electrons. Moreover, the Tanabe hypothesis predicted that the A-site cation was a basic surface site, and the CO 2 -TPD results revealed that Ni 2+ has the strongest surface basicity. Ni 2 V 2 O 7 exhibited much higher CO yield of 33.1 μmol/g, compared to Co 2 V 2 O 7 (16.7 μmol/g) and Zn 2 V 2 O 7 (12.9 μmol/g). Cu 2 V 2 O 7 was not suitable for CO 2 reduction due to its positive conduction band position caused by splitting the Cu 3d orbital. Altogether, this study contributes to deeply understanding metal vanadates for photocatalytic CO 2 reduction. The substitution of A-site cations not only changed the band structure and electronic structure of vanadate, affecting the occurrence of photocatalytic CO 2 reduction in the aspect thermodynamics, but also adjust the catalyst surface basicity, facilitating the adsorption and activation of CO 2 in the aspect of kinetics. The present research provides useful information for designing a new photocatalyst for CO 2 reduction under visible light. • A-site replacement of A 2 V 2 O 7 (A = Co, Ni, Cu, Zn) could turn both electronic structure and surface basicity. • Based on Tanabe hypothesis and TPD results, Ni 2 V 2 O 7 had the strongest surface basicity among the samples. • Ni 2 V 2 O 7 exhibits much higher activities for photocatalytic CO 2 reduction than Co 2 V 2 O 7 and Zn 2 V 2 O 7 under visible light illumination.