Understanding the enhanced catalytic activity of bimetallic AuCu/TiO2 in CO2 adsorption and activation: a density functional theory study

Abstract

Photoreduction of CO₂ to hydrocarbons has lately attracted increased attention. Understanding the reaction mechanism of photocatalytic reduction of CO₂ is crucial for the development of CO₂ photocatalysts. CO₂ adsorption and activation are the first steps of CO₂ photoreduction. In this work, the adsorption and activation of CO₂ on TiO₂-supported Au and Au–Cu clusters were studied using density functional theory (DFT) calculations to identify the key factors for improving its adsorption and activation. The presence of Cu atoms was found to have great significance in the adsorption and activation of CO₂, and the Cu7 atom on the Au₇Cu₃/TiO₂(101) surface exhibited the strongest CO₂ adsorption ability. By analyzing the surface electronic structure, we found that the up-shift of the d-band center toward the Fermi level in the presence of Cu atoms increased the binding strength of CO₂. Additionally, the Cu atoms were positively charged on the Au₇Cu₃/TiO₂(101) surface and promoted the adsorption of CO₂ by increasing the electrostatic attraction between the O atom of CO₂ and the Cu atom. Therefore, compared to the Au₁₀/TiO₂(101) surface, the activity of the Au₇Cu₃/TiO₂(101) surface can be definitely improved. Our results can provide useful insights into the design and development of more efficient bimetallic cluster supported TiO₂ photocatalysts, which are used as catalysts for the synthesis of hydrocarbon fuels by CO₂ hydrogenation.