MgO and Au nanoparticle Co-modified g-C3N4 photocatalysts for enhanced photoreduction of CO2 with H2O

The photoreduction of CO2 to achieve high-value-added hydrocarbons under simulated sunlight irradiation is advantageous, but challenging. In this study, a series of MgO and Au nanoparticle-co-modified g-C3N4 photocatalysts were synthesized and subsequently applied for the photocatalytic reduction of CO2 with H2O under simulated solar irradiation. The best photocatalytic performance was demonstrated by the Au and 3% MgO-co-modified g-C3N4 photocatalysts with CO, CH4, CH3OH, and CH3CHO yields of 423.9, 83.2, 47.2, and 130.4 μmol/g, respectively, in a 3-h reaction. We investigated the effects of MgO and Au as cocatalysts on photocatalytic behaviors, respectively. The characterizations and experimental results showed that the enhanced photocatalytic activity was due to the synergistic effect among the components of the ternary photocatalyst. The cocatalyst MgO can activate CO2 (adsorbed at the interface between the MgO and Au particles), and the Mg-N bonds formed in the MgO-CN nanosheets played an important role in the charge transfer. Meanwhile, the Au particles that were modified into MgO/g-C3N4 can increase the absorption of visible light via the surface plasmon resonance effect and further reduce the activation energies of the photoreduction of CO2 using H2O. This study provided an effective method for the modification of traditional primary photocatalysts with promising performance for photocatalytic CO2 reduction.