Boosting CO₂ Electroreduction to C₂H₄ via Unconventional Hybridization: High-Order Ce⁴⁺ 4f and O 2p Interaction in Ce-Cu₂O for Stabilizing Cu⁺

Abstract

Efficient conversion of carbon dioxide (CO 2 ) into value-added materials and feedstocks, powered by renewable electricity, presents a promising strategy to reduce greenhouse gas emissions and close the anthropogenic carbon loop. Recently, there has been intense interest in Cu 2 O-based catalysts for the CO 2 reduction reaction (CO 2 RR), owing to their capabilities in enhancing C−C coupling. However, the electrochemical instability of Cu + in Cu 2 O leads to its inevitable reduction to Cu 0 , resulting in poor selectivity for C 2+ products. Herein, we propose an unconventional and feasible strategy for stabilizing Cu + through the construction of a Ce 4+ 4f−O 2p− Cu + 3d network structure in Ce-Cu 2 O. Experimental results and theoretical calculations confirm that the unconventional orbital hybridization near E f based on the high-order Ce 4+ 4f and 2p can more effectively inhibit the leaching of lattice oxygen, thereby stabilizing Cu + in Ce-Cu 2 O, compared with traditional d−p hybridization. Compared to pure Cu 2 O, the Ce-Cu 2 O catalyst increased the ratio of C 2 H 4 /CO by 1.69-fold during the CO 2 RR at −1.3 V. Furthermore, in situ and ex situ spectroscopic techniques were utilized to track the oxidation valency of copper under CO 2 RR conditions with time resolution, identifying the well-maintained Cu + species in the Ce-Cu 2 O catalyst. This work not only presents an avenue to CO 2 RR catalyst design involving the high-order 4f and 2p orbital hybridization but also provides deep insights into the metal-oxidation-statedependent selectivity of catalysts.

Core–shell structures of Cu2O constructed by carbon quantum dots as high-performance zinc-ion battery cathodes

“…As shown in Fig. 2b, the characteristic peak of Cu 2 O is located at 220 cm −1 in the Raman spectra, 34 and its intensity decreases with the increase in CDs content. The peak of Cu 2 O in Cu 2 O-CDs-30 largely disappears, which is attributed to the thicker shells and agglomerated clumps formed by the excess CDs masking the surface Raman effect of Cu 2 O.…”

Deciphering the Stability Mechanism of Cu Active Sites in CO2 Electroreduction via Suppression of Antibonding Orbital Occupancy in the O 2p-Cu 3d Hybridization

“…As a result, these surface defects are likely responsible for the pronounced differences observed in surface-adsorbed oxygen between Cu v -Cu 2 O and pure Cu 2 O. Notably, the lattice O desorption temperature for Cu v -Cu 2 O (534.9 °C) markedly exceeds that of the pure Cu 2 O (424.2 °C), indicating a more robust Cu–O bond in the former . A minor temperature peak observed for pure Cu 2 O at 333.6 °C seems to be machine noise.…”

“…Moreover, E o for Cu v -Cu 2 O is higher by 0.1–0.3 eV than that for pure Cu 2 O when one or two O atoms are removed from the bulk surface (Figure g). This hints at a more challenging generation of oxygen defects in Cu v -Cu 2 O, further indicating the higher stability of Cu–O bond in Cu v -Cu 2 O. , The specific configurations of the O defects are detailed in Figure S7. The findings suggest that the uplifted energy level of 2p of O due to Cu defects curtails the leaching of lattice O.…”

“…In the wake of stringent greenhouse gas emission standards, the electroreduction of CO 2 has garnered substantial attention. Beyond the environmental impetus, the conversion of CO 2 through renewable electricity offers a promising avenue to produce high-value chemicals, presenting both an economic and sustainability incentive. − Among the gamut of CO 2 reduction reaction (CO 2 RR) products, ethylene stands out due to its pronounced demand and its seamless integration potential within the existing industrial infrastructure. , Currently, Cu-based catalysts are lauded for their exceptional ability to produce ethylene, which should be attributed to their optimal C–C coupling energy. − In addition, both density functional theory (DFT) studies and experimental data highlight that the concurrent presence of Cu 0 and Cu + critically enhances the selectivity toward C 2 H 4 . , Despite the critical role of Cu + species in CO 2 RR, its thermodynamic instability predisposes it to reduction to Cu 0 . ,− To address this, strategies such as elemental doping, , microenvironmental regulation, , and organic ligand stabilization have emerged. However, the quest for a robust and advanced stabilization mechanism for Cu + during the CO 2 RR remains ongoing, beckoning further exploration and innovation in this vital area.…”

“…The amplification of O 2p and Cu + 3d orbital hybridization emerges as a potent mechanism to bolster the Cu–O bond, thereby stabilizing Cu + sites. ,,, This hybridization yields a fully occupied bonding orbital at the low energy level, while also manifesting a partially occupied antibonding orbital at the high energy level . Intriguingly, the antibonding orbital occupancy state at active sites is pivotal in modulating bonding strength. − For instance, Yu et al have demonstrated that diminishing the antibonding orbital occupancy of Se 4p and H 1s orbitals augments hydrogen adsorption, thereby enhancing the H 2 evolution reaction .…”