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.