Enhancing C-C bond formation by surface strain: a computational investigation for C2 and C3 intermediate formation on strained Cu surfaces

In this study, 121 copper(100) models with surface strain are used for simulating C-C bond formation by CO2 electrochemical reduction. Its catalytic properties have been characterized by considering the formation energies of various C1 and C2 intermediates, and critical reaction steps along the CO2/CO reduction reaction paths. It turns out that the surface strain with one compressed axis and one elongated axis is geometrically beneficial for C2 product formation. The surface strain stabilizes the CO binding on the bridge sites (*CObridge) and the C2 intermediates - *OCCOH and *OCCO, and maintains a low activation energy of CO-CO coupling at around 0.57 to 0.69 eV. The surface strain also suppresses *H formation, which would allow more *CO formation leading to a higher CO2/CO reduction efficiency. Furthermore, the displaced copper models only exist under high compressing strain and were found to have great potential to activate CO2/CO into C3 products under a mild condition during the electrochemical reduction process. The activation energies for the third carbon atom coupling with C2 intermediates are 0.45-0.63 eV subject to the condition of the surface strain. The atomic arrangement with an adjacent rectangle and parallelogram is found to play an important role in producing C3 products. The selectivity of C-C bond formation induced by surface strain is demonstrated by this computational study.