Electrochemical Reduction of Carbon Dioxide at TiO₂/Au Nanocomposites

Herein, we report on the facile synthesis of nanocomposite consisting of TiO₂ and Au nanoparticles (NPs) via a tailored galvanic replacement reaction (GRR). The electrocatalytic activity of the synthesized TiO₂/Au nanocomposites for CO₂ reduction was investigated in an aqueous solution using various electrochemical methods. Our results demonstrated that the TiO₂/Au nanocomposites formed through the GRR process exhibited improved catalytic activities for CO₂ reduction, while generating more hydrocarbon molecules than the typical formation of CO in contrast to polycrystalline Au. GC analysis and NMR spectroscopy revealed that CO and CH₄ were the gas products, whereas HCOO^-, CH₃COO^-, CH₃OH, and CH₃CH₂OH were the liquid products from the CO₂ reduction at different cathodic potentials. This remarkable change was further studied using the density functional theory (DFT) calculations, showing that the TiO₂/Au nanocomposites may increase the binding energy of the formed ^·CO intermediate and reduce the free energy compared to Au, thus favoring the downstream generation of multicarbon products. The TiO₂/Au nanocomposites have high catalytic activity and excellent stability and are easy to fabricate, indicating that the developed catalyst has potential application in the electrochemical reduction of CO₂ to value-added products.