Disruption Symmetric Crystal Structure Favoring Photocatalytic CO2 Reduction: Reduced *COOH Formation Energy Barrier on Al Doped CuS/TiO2

Abstract

How to break the C═O bond and reduce the energy barrier of *COOH formation is the key to triggering the photocatalytic CO2 reduction (PCR) reaction and subsequent proton-electron processes, which is as important as overcoming high recombination rate of photocarriers. In order to solve this issue, the symmetric structure of CuS/TiO2 is destroyed by S vacancy and Al doping (denoted as Al-CuS/TiO2), which significantly expands the electron localization range and promotes the cis-coordination splitting of Cu 3d orbits. The experimental results show that the CO yield selectivity of ≈90.68% and yield of ≈335.68 µmol·g−1·h−1 on Al-CuS/TiO2. The redistribution of Cu electron states in specific d/s/p orbitals increases the adsorption of CO2 and reduces the reaction energy barrier of *COOH intermediates, while effectively breaking the C═O bond. Doped Al atoms also serve as adsorption sites for H2O molecules, effectively interleaving the competition with photocatalytic CO2 reduction at the Cu sites is effectively staggered. This study provides a new approach to reduce the energy barrier of *COOH formation and to accelerate the photocarrier migration by destroying local symmetry to adjust the crystal structure, which is important for further improving the activity and selectivity of PCR.