Enriching the Local Concentration of CO Intermediates on Cu Cavities for the Electrocatalytic Reduction of CO 2 to C 2+ Products.

The electrochemical carbon-dioxide reduction reaction (CO 2 RR) to high-value multi-carbon (C 2+ ) chemicals provides a hopeful approach to store renewable energy and close the carbon cycle. Although copper-based catalysts with a porous architecture are considered potential electrocatalysts for CO 2 reduction to C 2+ chemicals, challenges remain in achieving high selectivity and partial current density simultaneously for practical application. Here, the porous Cu catalysts with a cavity structure by in situ electrochemical-reducing Cu 2 O cavities are developed for high-performance conversion of CO 2 to C 2+ fuels. The as-described catalysts exhibit a high C 2+ Faradaic efficiency and partial current density of 75.6 ± 1.8% and 605 ± 14 mA cm -2 , respectively, at a low applied potential (-0.59 V vs RHE) in a microfluidic flow cell. Furthermore, in situ Raman tests and finite element simulation indicated that the cavity structure can enrich the local concentration of CO intermediates, thus promoting the C-C coupling process. More importantly, the C-C coupling should be major through the *CO-*CHO pathway as demonstrated by the electrochemical Raman spectra and density functional theory calculations. This work can provide ideas and insights into designing high-performance electrocatalysts for producing C 2+ compounds and highlight the important effect of in situ characterization for uncovering the reaction mechanism.