Selectively Adsorbed Mercaptoethanesulfonic Acid on Au/TiO2 Enhances the Yield and Selectivity of Photocatalytic Reduction of Carbon Dioxide

The photocatalytic reduction of carbon dioxide (CO2RR) is of paramount importance in the energy industry and environmental protection. Developing highly efficient catalysts plays a central role in advancing CO2RR for practical applications, and a Au/TiO2 heterostructure has emerged as a prominent photocatalyst in CO2RR. However, there is still a need to improve the reaction efficiency and selectivity of this heterostructure to realize its full potential in practical applications. Herein, a significant enhancement in the total gas-production rate on the Au/TiO2 heterostructure is achieved by selectively adsorbing thiol molecules, specifically mercaptoethanesulfonic acid, onto the gold surface. Remarkably, the selectivity toward carbon monoxide has also improved from 62.3 to 79.3%. Notably, the reaction rate and selectivity are strongly influenced by the choice of thiol molecules, their concentration, and the wavelength of light used for illumination. The improved reaction efficiency and selectivity can be attributed to the promotion of charge transfer at the Au–TiO2 interface induced by molecular adsorption of thiols. This phenomenon leads to enhanced performance in the photocatalytic CO2RR process. Importantly, this work presents a simple, convenient, cost-effective, and controllable strategy to improve the reaction efficiency and selectivity of photocatalytic CO2RR on the Au/TiO2 heterostructure. Furthermore, this strategy holds promise for application in various other heterogeneous photocatalytic systems in the near future.