How Strain Alters CO2 Electroreduction on Model Cu(001) Surfaces

Carbon dioxide electrolysis powered by renewable energy is a potentially attractive approach to close the carbon cycle and produce key chemical feedstocks. Here, we demonstrate the substantial influence of tensile strain on the selectivity of CO2 reduction toward higher value-added, multicarbon products by modulating the residual mismatch strain of Cu(001) thin film catalysts grown epitaxially on single-crystal Si substrates. By decreasing film thickness from 100 to 20 nm, up to 0.22% tensile strain is introduced in-plane, shifting the measured Cu d-band center at the surface upward, in good agreement with theory. CO2 electrolysis at moderate overpotential (-0.9 V vs reversible hydrogen electrode (RHE)) in 0.1 M KHCO3 electrolyte reveals that the shift in d-band center results in the suppression of single-carbon products, while activity for multicarbon products is maintained. Examination of the ratio of partial current densities for multicarbon products relative to CO and CH4 suggests increased CO insertion and hydrogenation on the tensile-strained Cu(001) surface, driven by a change in the adsorbate bonding because of an increased interaction with the upshifted d-band. This work provides direct experimental evidence on model thin film CO2 catalysts that strain can be systematically manipulated as a valuable tool, independent of catalyst composition, for the design of efficient CO2 electrocatalysts toward energy-dense products.