Abstract <p>As known, the electrochemical conversion of CO₂ toward high-valued productions (such as C₂₊ products) strongly depend on accurate construction of Cu⁰/Cu⁺ interfaces, but the complex synthesis hinders practical application. In this work, we adopt a simple solid-state pyrolysis synthesis to construct CuO/Cu₂O, Cu/Cu₂O heterojunction electrocatalysts via altering the calcination temperature. The as-prepared CuO/Cu₂O catalyst demonstrates exceptional performance for CO₂ reduction reaction (CO₂RR), achieving a remarkable maximum C₂ Faradaic efficiency (FE) of 87.6% at a high current density of 1.0 A cm⁻² and even the FE of C₂ still reaches 73.0% at 1.2 A cm⁻². Moreover, the catalyst maintains excellent electrochemical stability for over &#xa0;95&#xa0;h at 1.0 A cm⁻² with negligible attenuation. XPS and XAFS characterizations reveal that the electroreduced CuO/Cu₂O catalyst retains abundant Cu⁰/Cu⁺ interfaces and thus accelerates the reaction kinetics of C–C coupling. Furthermore, in situ spectroscopic studies indicate that abundant Cu⁰/Cu⁺ interfaces significantly promote the activation of CO₂ to *CO, thereby facilitating the formation of multi-carbon products.</p> Graphical abstract <p></p>