Synergistic promotion of proton relay and *CO hydrogenation in Cu-Zn tandem catalysts for highly efficient electrocatalytic CO₂-to-CH₄ conversion

The eight-electron transfer pathway required for CH₄ formation in electrocatalytic carbon dioxide reduction reaction (eCO₂RR) is kinetically slow, which leads to poor reaction selectivity. In this work, a CuZn-BDC-NH₂ precursor was synthesized via a facile solvothermal method, and a series of CuZn@C materials were prepared by calcination under varying temperature conditions (700, 800, and 900 °C) utilizing the high-temperature volatility of Zn. Among them, the CuZn800@C sample demonstrates the best CH₄ electro-reduction performance, achieving a methane Faradaic efficiency (FE) of 64.5% and a partial current density of −429.1 mA·cm⁻² at a potential of −1.7 V vs. reversible hydrogen electrode (RHE), along with excellent stability, showing only a slight performance decline after a 24-h test. Through in situ infrared spectroscopy and density functional theory (DFT) calculations, electrocatalytic mechanism investigations reveal that Zn and Cu form a tandem reaction system. Zn sites promote water splitting to provide protons, while Cu sites reduce the energy barrier for *CO hydrogenation. Moreover, Zn and Cu can constitute dual active sites that enhance CO₂ adsorption, thereby boosting subsequent reactions. This work develops a new strategy for designing high performance Cu-based methanation catalysts.