Deciphering the Stability Mechanism of Cu Active Sites in CO₂ 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 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.

Insights into the Origin of Activity Enhancement via Tuning Electronic Structure of Cu2O towards Electrocatalytic Ammonia Synthesis

“…The concentration of each halogen in the Cu2O-halogen catalysts was also made by XPS (Table S1). In Figure 3b, the Cu 2p fine spectrum shows two peaks with binding energies of 932.3 eV and 952.6 eV, attributed to Cu 0 /Cu + 2p3/2 and Cu 0 /Cu + 2p1/2, respectively, typical XPS binding energy peak positions of Cu + , with vibrationally excited companion peaks belonging to Cu 2+ seen at 942.5 eV and 962.0 eV, indicating the presence of copper oxide on the surface [24][25][26][27]. The presence of CuO in the materials may be due to two reasons: firstly, the samples were stored for a long time before the test, leading to surface oxidation of Cu2O to CuO; secondly, residual particulate impurities on the surface of Cu2O contained a small amount of Cu 2+ substances.…”

Enhancing CO2 Electroreduction Performance through Si-Doped CuO: Stabilization of Cu+/Cu0 Sites and Improved C2 Product Selectivity

“…The electrochemical reduction of CO 2 (CO 2 RR) represents a pivotal advancement toward achieving sustainable carbon neutrality, − facilitating the transformation of greenhouse gases into valuable fuels and chemical precursors. − Among the array of products, multicarbon (C 2 ) products stand out due to their high energy densities and significant economic value, marking them as prime targets for industrial utilization. − Currently, copper-based (Cu) catalysts are distinguished for their unique ability to promote C–C coupling, making them the sole class of materials proficient in selectively converting CO 2 to valuable C 2 products such as ethylene and ethanol. ,,− However, these materials often undergo uncontrollable structural changes during CO 2 RR, jeopardizing the integrity of active sites and leading to diminished catalytic efficiency or complete activity loss. , Interestingly, the CuO x catalysts have demonstrated robust performance, benefiting from certain restructuring effects. ,, Notably, the coexistence of Cu + and Cu 0 states has been identified as crucial for enhancing the selectivity to C 2 products. ,− However, the thermodynamic instability of Cu + predisposes it to reduction to Cu 0 under operational conditions, posing significant stability challenges. To address these challenges, approaches including the deployment of organic ligands, the integration of auxiliary metals, and the utilization of Cu-based catalyst have been explored. ,,− However, these methods frequently encounter limitations in catalytic performance, stability, and capacity to scale up.…”