Abstract:

Electrocatalytic reduction of CO₂ (CO₂RR) to multicarbon products is an efficient approach for addressing the energy crisis and achieving carbon neutrality. In H-cells, achieving high-current C₂ products is challenging because of the inefficient mass transfer of the catalyst and the presence of the hydrogen evolution reaction (HER). In this study, dendritic Cu/Cu₂O with abundant Cu⁰/Cu⁺ interfaces and numerous dendritic curves was synthesized in a CO₂ atmosphere, resulting in the high selectivity and current density of the C₂ products. Dendritic Cu/Cu₂O achieved a C₂ Faradaic efficiency of 69.8% and a C₂ partial current density of 129.5 mA cm^‒2 in an H-cell. Finite element simulations showed that a dendritic structure with a high curvature generates a strong electric field, leading to a localized CO₂ concentration. Additionally, DRT analysis showed that a dendritic structure with a high curvature actively adsorbed the surrounding high concentration of CO₂, enhancing the mass transfer rate and achieving a high current density. During the experiment, the impact of the electronic structure on the performance of the catalyst was investigated by varying the atomic ratio of Cu⁰/Cu⁺ on the catalyst surface, which resulted in improved ethylene selectivity. Under the optimal atomic ratio of Cu⁰/Cu⁺, the charge transfer resistance was minimized, and the desorption rate of the intermediates was low, favoring C₂ generation. Density functional theory calculations indicated that the Cu⁰/Cu⁺ interfaces exhibited a lower Gibbs free energy for the rate-determining step, enhancing C₂H₄ formation. The Cu/Cu₂O catalyst also exhibited a low Cu d-band center, which enhanced the adsorption stability of *CO on the surface and facilitated C₂ formation. This observation explained the higher yield of C₂ products at the Cu⁰/Cu⁺ interface than that of H₂ under rapid mass transfer. The results of the net present value model showed that the H-cell holds promising industrial prospects, contingent upon it being a catalyst with both high selectivity and high current density. This approach of integrating the structure and composition provides new insights for advancing the CO₂RR towards high-current C₂ products.

Key words: Reduction of CO₂, High current, Dendritic structure, Cu/Cu₂O, H-cell