Mg-doped SrTiO3 photocatalyst with Ag-Co cocatalyst for enhanced selective conversion of CO2 to CO using H2O as the electron donor

Photocatalytic conversion of CO2 by H2O is a promising method for solving energy and environmental problems. In this context, efficient photocatalysts that facilitate the selective conversion of CO2 to the value-added chemical CO are essential. In this study, for the first time in the literature, we used an Mg-doped SrTiO3 photocatalyst (Mg-SrTiO3) for the photocatalytic conversion of CO2 to CO using H2O as the electron donor under monochromatic UV-light irradiation at 365 nm. Compared to pristine SrTiO3, Mg-SrTiO3, which was prepared via a flux method, exhibited dramatically enhanced conversion of CO2 to CO in the presence of an Ag-Co cocatalyst. Moreover, the selectivity toward CO evolution was >99%, which indicates suppression of the unnecessary and competitive H-2 evolution. Scanning electron microscopy of Mg-SrTiO3 revealed edge-shaved cubic particles, which were correlated to the anisotropic distribution of photogenerated electrons and holes and the consequent enhancement of photocatalytic activity. Furthermore, the Mg-doping temperature and amount used to prepare Mg-SrTiO3 influenced the substitution of Ti4+ sites by Mg2+ in the bulk of SrTiO3, thereby affecting the CO evolution. The apparent quantum efficiency of optimal Mg-SrTiO3 in the photocatalytic conversion of CO2 was determined to be 0.05%.