Optimized catalytic properties and reactant adsorption energy play a crucial role in promoting CO2 electrocatalysis. Herein, Cu7S4/Cu undergoes in situ dynamic restructuring to generate S-Cu2O/Cu hybrid catalyst for effective electrochemical CO2 reduction to formate that outperforms Cu2O/Cu and Cu7S4. Thermodynamic and experimental analyses reveal that the optimized adsorption of the HCOO* intermediate on S-Cu2O/Cu is regulated and the H2 pathway (surface H) is suppressed by S-doping. Meanwhile, Cu7S4/Cu nanoflowers create abundant grain boundaries for ECR and strengthen the CO2 adsorption by inducing Cu. These findings provide a new perspective on synthetic methods for various electrocatalytic reduction processes.