The Co/CoO Interface Catalyzes the Synthesis of Acetic Acid from CO2: A Combined Experimental and Density Functional Theory Study

The selective conversion of CO2 into multicarbon products, particularly for the oxygen-containing compound acetic acid, is critical for sustainable chemical synthesis, yet achieving high selectivity remains a challenge. Here, we demonstrate that a Co/CoO heterointerface serves as a highly active site for the selective synthesis of acetic acid from CO2 by experimental and density functional theory (DFT) study. Experimental results show that the Co/CoO interface achieves 61.67% selectivity for acetic acid, which is higher than the values of 0% and 24.39% for single-phase face-centered cubic (FCC) Co and hexagonal close-packed (HCP) Co, respectively. DFT calculations reveal that interfacial lattice oxygen in Co/CoO induces a geometric reconfiguration of CO2 adsorption, shifting the adsorbed CO2 configuration from a "side-on" to a "face-on" orientation with an interfacial angle of 45°. This transition enhances orbital hybridization in the xy plane, stabilizes CO2 adsorption, and lowers the energy barrier for C─C coupling. Crystal orbital Hamiltonian population analysis quantifies the strengthened O─C bonding (─ICOHP = 9.97 eV) and highlights the dominance of xy-directional orbitals, establishing the interfacial angle as a descriptor for the selective production of acetic acid from CO2. This study reveals, at the electronic levels, how the Co/CoO interface promotes CO2 reduction toward oxygenated C2+ products (e.g., acetic acid), thereby offering a fundament for the rational design of catalysts targeting valuable acetic acid.