Facile Synthesis of Co@TiO2/C Hybrid Catalyst and Its Application to Photocatalytic Reduction of CO2 under Visible-Light Irradiation

Solar-light-driven reduction of CO₂ into energy-rich carbon-based products has attracted wide attention, with specific importance attached to the development of highly efficient catalysts and the establishing new photocataytic systems. Herein, we develop a facile approach to embed Co nanoparticles to hollow TiO₂ nanorods (HTONR) to form a hybrid catalyst (Co/HTONR) by one-step calcination of a self-assembly of cobalt(II) and tetrabutyl titanate. After coating with a carbon nanolayer, the photocatalytic activity of the material towards CO₂-to-CO conversion was boosted, CO generation rate of up to 54,000 μmol h^-1 g^-1 was observed in the first hour of reaction. The average production rate of 28,500 μmol h^-1 g^-1 with a selectivity of 78.1% for the transformation can be achieved even though the irradiation time was prolonged to 3 h. The excellent efficiency was partially attributed to the carbon nanolayer improving the electron transmission properties and accordingly enhanced the catalytic activities comparison to that of Co@TiO₂. Additionally, the introduction of hollow TiO₂ nanorods increases the local CO₂ concentration owing to its adsorption. And existence of -OH group on the surface of TiO₂ facilitated the key kinetic step of proton transfer during CO₂ photoreduction, which is further confirmed by an investigation of catalytic efficiencies as a function of amount of H₂O.