Modulating the Reaction Configuration by Breaking the Structural Symmetry of Active Sites for Efficient Photocatalytic Reduction of Low-concentration CO2

Abstract

Photocatalytic conversion of low-concentration CO₂ is considered as a promising way to simultaneously mitigate the environmental and energy issues. However, the weak CO₂ adsorption and tough CO₂ activation process seriously compromise the CO production, due to the chemical inertness of CO₂ molecule and the formed fragile metal-C/O bond. Herein, we designed and fabricated oxygen vacancy contained Co₃ O₄ hollow nanoparticles on ordered macroporous N-doped carbon framework (Vo-HCo₃ O₄ /OMNC) towards photoreduction of low-concentration CO₂ . In situ spectra and ab initio molecular dynamics simulations reveal that the constructed oxygen vacancy is able to break the local structural symmetry of Co-O-Co sites. The formation of asymmetric active site switches the CO₂ configuration from a single-site linear model to a multiple-sites bending one with a highly stable configuration, enhancing the binding and structural polarization of CO₂ molecules. As a result, Vo-HCo₃ O₄ /OMNC shows unprecedent activity in the photocatalytic conversion of low-concentration CO₂ (10 % CO₂ /Ar) under laboratory light source or even natural sunlight, affording a syngas yield of 337.8 or 95.2 mmol g^-1 h^-1 , respectively, with an apparent quantum yield up to 4.2 %.

Keywords: CO2 Reduction; Metal-Organic Frameworks; Oxygen Vacancy; Photocatalysis; Synthesis Gas.