In Situ Formed Metal Oxide/Metal Interface Enhanced C–C Coupling in CO2 Reduction into CH3COOH over Hexagonal Closed-Packed Cobalt

Conversion of CO2 into value-added chemicals and fuels is one promising method for mitigating global warming and fossil fuel depletion. However, hindered by the dual barriers of CO2 activation and selective catalytic C–C coupling, hydrogenation of CO2 into multicarbon products, especially for organic acids, still remains a great challenge. In this work, an acetate yield of 9.5% from direct CO2 reduction was obtained via a specific hexagonal closed-packed cobalt (HCP-Co) catalyst under hydrothermal conditions. Results showed that the in situ formed CoO/Co interface was the key for the CO2 activation and subsequent C–C coupling. The unique properties of hydrothermal reactions were found to modulate the proportion of metal oxide/metal on the catalyst surface, which then gave a stable formation of CoO/Co interface. A plausible reaction pathway is also proposed based on the time-dependent experiments and DFT calculation, in which *CH2 and HCOO as the intermediates were combined to form CH3COO– through the carbene reaction. This study provides a robust approach for C–C coupling in CO2 hydrogenation without noble metal catalysts, which is essential for the practical application.