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

Abstract

Copper-based catalysts, hallmarked by their ideal C–C coupling energy facilitated by the symbiotic presence of Cu+ and Cu0 active sites, are poised to revolutionize the selective electrochemical reduction of CO2 to C2H4. Regrettably, these catalysts are beleaguered by the unavoidable diminution of Cu+ to Cu0 during the reaction process, resulting in suboptimal C2H4 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 Cu2O, 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 Cu2O (Cuv-Cu2O). Empirically, Cuv-Cu2O has outperformed its pure Cu2O counterpart, exhibiting a prominent C2H4/CO ratio of 1.69 as opposed to 1.01, without conceding significant ground in C2H4 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

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