The electrochemical carbon dioxide reduction reaction (CO2RR) to formate is of great interest in the field of electrochemical energy. Cu-based material is an appealing electrocatalyst for the CO2RR. However, retaining Cu2+ under the high cathodic potential of CO2RR remains a great challenge, leading to low electrocatalytic selectivity, activity, and stability. Herein, inspired by corrosion science, a sacrificial protection strategy to stabilize interfacial crystalline CuO through embedding of active amorphous SnO2 (c-CuO/a-SnO2) is reported, which greatly boosts the electrocatalytic sensitivity, activity, and stability for CO2RR to formate. The as-made hybrid catalyst can achieve superior high selectivity for CO2RR to formate with a remarkable Faradaic efficiency (FE) of 96.7%, and a superhigh current density of over 1 A cm−2 that far outperforms industrial benchmarks (FE > 90%, current density > 300 mA cm−2). In situ X-ray absorption spectroscopy (XAS) and X-ray diffractionexperimental and theoretical calculation results reveal that the broadened s-orbital in interfacial a-SnO2 offers the lower orbital for extra electrons than Cu2+, which can effectively retain nearby Cu2+, and the high active interface significantly lowers the energy barrier of the limited step (*CO2 → *HCOO) and enhances the selectivity and activity for CO2RR to formate.