Photocatalytic Oxidative Coupling of Methane to Ethane Using CO2 as a Soft Oxidant Over the Au/TiO2‐Vo Nanosheets

Herein, we first report a photocatalytic OCM using CO2 as a soft oxidant for C2H6 production under mild conditions, where an efficient photocatalyst with unique interface sites is constructed to facilitate CO2 adsorption and activation, while concurrently boosting CH4 dissociation. As a prototype, the Au quantum dots anchored on oxygen‐deficient TiO2 nanosheets are fabricated, where the Au‐Vo‐Ti interface sites for CO2 adsorption and activation are collectively disclosed by in situ Kelvin probe force microscopy, quasi in situ X‐ray photoelectron spectroscopy and theoretical calculations. Compared with single metal site, the Au‐Vo‐Ti interface sites exhibit the lower CO2 adsorption energy and decrease the energy barrier of the *CO2 hydrogenation step from 1.05 to 0.77 eV via Au‐C and Ti‐O dual‐site bonding. The adsorbed CO2 reduces the energy barrier of *CH4 dissociation to *CH3 from 2.13 to 1.59 eV, contributing to CH4 oxidation. Additionally, in situ Fourier‐transform infrared spectroscopy unveils the Au site facilitates ethane production by engaging in *CH3‐Au interaction and accelerating CH3‐CH3 coupling. Thus, the photocatalyst demonstrates a high C2H6 evolution rate of 2.60 mmol g‐1 h‐1 for OCM using CO2 as the soft oxidant, surpassing most of previously reported photocatalysts regardless of OCM and nonoxidative coupling of methane.