Molecular‐Level Insight Into CO Dimerization on Cu(100) Through Explicit Consideration of Surface Diffusion

Electrochemical reduction of CO 2 to multicarbon products is widely regarded as pivotal to the sustainable production of fuels and value‐added chemicals. A detailed understanding of the CO dimerization mechanism on Cu‐based metal catalysts is indispensable for developing highly active reaction systems; however, most previous studies have focused exclusively on the CC bond formation step. Herein, we comprehensively investigate the CO dimerization process by explicitly accounting for the surface diffusion of CO molecules using first‐principles calculations. The activation barriers for CO migration from an atop site to a bridge site and from a bridge site to a hollow site are 0.040 and 0.061 eV, respectively, at the Cu(100) surface. These values are approximately one order of magnitude smaller than the activation barrier for the CC bond formation step (0.469 eV), indicating that surface diffusion is energetically facile. Therefore, surface diffusion is required to generate neighboring CO species prior to CC coupling, but it does not appreciably contribute to the reaction activation energy. Additional calculations on heterometal‐doped Cu surfaces showed that the CO migration barriers remained much smaller than the CC bond‐formation barriers, indicating that the reaction activation energy is also governed mainly by CC bond formation in Cu‐alloy systems.