Compressive strain in Cu catalysts: Enhancing generation of C products in electrochemical CO reduction.

Elastic strain in Cu catalysts enhances their selectivity for the electrochemical CO reduction reaction (eCORR), particularly toward the formation of multicarbon (C) products. However, the reasons for this selectivity and the effect of catalyst precursors have not yet been clarified. Hence, we employed a redox strategy to induce strain on the surface of Cu nanocrystals. Oxidative transformation was employed to convert Cu nanocrystals to CuO nanocrystals; these were subsequently electrochemically reduced to form Cu catalysts, while maintaining their compressive strain. Using a flow cell configuration, a current density of 1 A/cm and Faradaic efficiency exceeding 80% were realized for the C products. The selectivity ratio of C/C1 was also remarkable at 9.9, surpassing that observed for the Cu catalyst under tensile strain by approximately 7.6 times. In-situ Raman and infrared spectroscopy revealed a decrease in the coverage of K ion-hydrated water (K·HO) on the compressively strained Cu catalysts, consistent with molecular dynamics simulations and density functional theory calculations. Finite element method simulations confirmed that reducing the coverage of coordinated K·HO water increased the probability of intermediate reactants interacting with the surface, thereby promoting efficient C-C coupling and enhancing the yield of C products. These findings provide valuable insights into targeted design strategies for Cu catalysts used in the eCORR.