Enhancement of CO2 reduction to C2+ products via local microenvironment modulation on Al2O3/Cu in neutral media

The electroreduction of carbon dioxide to multi-carbon products (C 2+ ) represents an effective pathway for achieving carbon cycling and high-density renewable energy storage. However, its practical implementation is challenged by excessively high C–C coupling reaction energy barriers and competitive hydrogen evolution reaction (HER). Modifications to the local microenvironment play a decisive role in the three-phase interface reaction of CO 2 electrocatalytic reduction. Therefore, this study employed an Al 2 O 3 -modified copper catalyst (Al 2 O 3 /Cu) to modulate the local reaction microenvironment, thereby promoting C 2+ formation. Notably, the optimized Al 2 O 3 /Cu catalyst achieved a remarkable C 2+ Faraday efficiency (FE) of 71.3% at −1.33 V vs. RHE (reversible hydrogen electrode; all potentials herein are referenced to RHE) in a neutral electrolyte using a flow cell, significantly outperforming unmodified Cu catalysts. This catalyst also demonstrated excellent catalytic stability, exceeding 56 h. Theoretical calculations and in situ spectroscopic characterization confirmed that introduced Al 2 O 3 species kinetically facilitate water dissociation and proton consumption, which is crucial for maintaining a transient localized high-pH environment under operating conditions. This alkaline microenvironment not only suppresses the HER but also stabilizes the critical Cu 2+ /Cu + active sites against over-reduction, while simultaneously lowering the energy barrier of C–C coupling reactions. This work underscores the critical role of dynamically modulating the localized chemical environment in neutral electrolytes for CO 2 reduction reactions (CO 2 RR), offering novel insights for designing such microenvironments.