Deciphering the Stability Mechanism of Cu Active Sites in CO 2 Electroreduction via Suppression of Antibonding Orbital Occupancy in the O 2p-Cu 3d Hybridization

Copper-based catalysts, hallmarked by their ideal C–C coupling energy facilitated by the symbiotic presence of Cu + and Cu 0 active sites, are poised to revolutionize the selective electrochemical reduction of CO 2 to C 2 H 4 . Regrettably, these catalysts are beleaguered by the unavoidable diminution of Cu + to Cu 0 during the reaction process, resulting in suboptimal C 2 H 4 yields. To circumvent this limitation, we have judiciously mitigated the antibonding orbital occupancy in the O 2p and Cu + 3d hybridization by introducing Cu defects into Cu 2 O, thereby augmenting the Cu–O bond strength to stabilize Cu + sites and further decipher the stabilization mechanism of Cu + . This structural refinement, illuminated by meticulous DFT calculations, fosters a heightened free energy threshold for the hydrogen evolution reaction (HER), while orchestrating a thermodynamically favorable milieu for enhanced C–C coupling within the Cu-deficient Cu 2 O (Cu v -Cu 2 O). Empirically, Cu v -Cu 2 O has outperformed its pure Cu 2 O counterpart, exhibiting a prominent C 2 H 4 /CO ratio of 1.69 as opposed to 1.01, without conceding significant ground in C 2 H 4 production over an 8 h span at −1.3 V vs RHE. This endeavor not only delineates the critical influence of antibonding orbital occupancy on bond strength and reveals the deep mechanism about Cu + sites but also charts a pioneering pathway in the realm of advanced materials design.