Surface engineering of Cu catalysts for electrochemical reduction of CO2 to value-added multi-carbon products

Copper (Cu) is the most efficient metal that can electrochemically convert CO 2 to various chemical feedstocks at reasonable efficiency. The activity and selectivity toward the CO 2 reduction reaction (CO 2 RR) largely depend on the surface sensitivity and electrokinetics of Cu catalysts. Surface engineering is achievable through tuning the structure and through crystal orientation. The Cu-surface modulation and tunings, e.g., controlled morphology, oxygen vacancies, and alloys on supports or substrates, propose different reaction tracks and intermediates, whereas common routes are ∗CO dimerization, C–C, and C 1 –C 2 coupling for the formation of C 2 and C 3 products. In this review, recent progress on the surface engineering of Cu-based catalysts is primarily recaptured and explained. The fragmentation, coalescence, and aggregation of Cu nanoparticles cause stability issues of Cu catalysts during the CO 2 RR, which has also been discussed. Finally, we summarize critical strategies and approaches to surface engineering of Cu-based catalysts for the efficient CO 2 RR. The continuous depletion of fossil fuels is the leading cause of global climate change due to the large accumulation of carbon dioxide (CO 2 ) in the atmosphere. Electrochemical CO 2 reduction into valuable products of fuels and chemicals would be a promising technical approach, and this relies on efficient electrocatalysts to accelerate CO 2 reduction reaction (CO 2 RR) and alleviate the energy crisis. As the most efficient metal, copper (Cu) has been widely explored for the CO 2 RR. However, a grand challenge for an ideal Cu-based catalyst is low faradaic efficiency (FE) for C 2+ products, and this highlights the CO 2 RR dependence and sensitivity to the surface of Cu catalysts. This review systematically summarizes the strategies for surface engineering of Cu catalysts and their effects on catalytic selectivity and activity for the CO 2 RR, which will have a substantial impact on the field to achieve the targets for commercial applications of CO 2 RR processes. Surface engineering is crucial to enhance the selectivity and activity for the efficient CO 2 reduction reaction (CO 2 RR) to a particular C 2+ product. This review recaptures recent progress on the surface engineering of Cu-based catalysts as the most extensively studied metal for the CO 2 RR, holding the great promise of neutralizing the carbon in the environment. Furthermore, how the optimized surface, phase effects, morphology, and configuration influence the catalytic performance and the reasons for Cu catalysts' instability are also discussed.