Stabilizing Cu2+ in perovskite via A-site modulation for efficient CO2 electrocatalysis to CH4

Cu²⁺ in copper-based catalysts can facilitate the hydrogenation of the CH₄ production pathway via the electrochemical carbon dioxide reduction reaction (ECRR). However, Cu²⁺ species in copper oxides are unstable and have been revealed to reduce to Cu⁰ under the applied cathodic potential. In this work, we reported an A-site modulation strategy to stabilize Cu²⁺ in perovskite for efficient ECRR to CH₄. After the introduction of Ca²⁺ in La₂CuO₄, the obtained LaCa_0.4CuO_3-δ is stable during ECRR. We achieved a 59.6 % ± 3.8 % CH₄ faradaic efficiency at -1.30 V versus reversible hydrogen electrode in H-cell and a partial current density of 155.0 mA/cm² in membrane electrode assembly. DFT calculations and in situ Raman spectroscopy show that Cu²⁺ facilitates the hydrogenation of *CH₂O to *CH₃O and the further production of CH₄. This work introduces an efficient strategy to stabilize Cu²⁺ and provides an understanding of Cu²⁺ in promoting ECRR to CH₄.