An improved CO coverage-dependent electrochemical interface model with an explicit solvent effect on Cu(100) is presented in this paper, by which theoretical insights into the potential-dependent C–C bond formation pathways occurring in CO₂ electrochemical reduction to C₂ products can be obtained. Our present studies indicate that CHO is a crucial intermediate toward C₁ products on Cu(111), and dimer OCCO is found to not be a viable species for the production of C₂ products on Cu(100). The reaction pathway of CHO with CO and CHO dimerization into dimers COCHO and CHOCHO may be C–C bond formation mechanisms at low overpotential. However, at medium overpotential, C–C bond coupling takes place preferentially through the reaction of COH with CO species and COH dimerization into dimers COCOH and COHCOH. The formed dimers COCHO, CHOCOH, and CHOCHO via reactions of CHO with CO, COH, and CHO species may lead to C₂ products, which are regarded as C–C bond formation mechanisms at high overpotential. The difference of obtained adsorption isotherms of CO on Cu(100) with that of Cu(111) may be able to explain the effect of the crystal face of Cu on product selectivity. The excellent consistencies between our present obtained conclusions and the available experimental reports and partial theoretical studies validate the reasonability of the present employed methodology, which can be also used to systematically study potential-dependent CO₂ electroreduction pathways toward C₂ products on Cu(100) or other metal catalysts.