Elastic strain controlling the activity and selectivity of CO₂electroreduction on Cu overlayers

Cu could reduce CO₂ into considerable amounts of hydrocarbons, the relative low efficiency and poor selectivity of which should be improved. Engineering the surface strain is a powerful method to improve the catalytic performance, however, generally clouded by the ensemble effect and ligand effect. In this research, we show how the elastic strain in Cu nanofilms varies the activity and selectivity of CO₂RR by virtue of the two-way shape memory effect of the NiTi substrate. For a 32 nm Cu overlayer, tensile strain improved the total CO₂RR faradaic efficiency from 65.02% to 76.48% and favored CH₄ generation. For a 5 nm Cu overlayer, strain impacted both HER and CO₂RR activities, where compressive strain induced more available active sites for CO₂ adsorption and resulted in 27% higher faradaic efficiency toward the CO₂RR. Based on DFT calculations and the derived positive correlation between free energy change and the energy barrier, the mechanism of strain-controlled electrocatalytic performance was also revealed.