Self-Assembled Controllable Cu-Based Perovskite/Calcium Oxide Hybrids with Strong Interfacial Interactions for Enhanced CH4 Electrosynthesis

Cu-based perovskite oxide catalysts show promise for CO₂ electromethanation, but suffer from unsatisfactory CH₄ selectivity and poor stability. Here, we report self-assembled, controllable Cu-based perovskite/calcium oxide hybrids with strongly interacting interfaces for high-performance CH₄ electrosynthesis. As proof-of-concept catalysts, the La₂CuO₄/(CaO)_x (x from 0.2 to 1.2) series has tunable CaO phase concentrations and thus controllable interface sizes. The La₂CuO₄ and CaO components are intimately connected at the interface, leading to strong interfacial interactions mainly manifested by marked electron transfer from Ca²⁺ to Cu²⁺. In CH₄ electrosynthesis, their activity and selectivity show a volcano-type dependence on the CaO phase concentrations and are positively correlated with the interface sizes. Among them, the La₂CuO₄/(CaO)_0.8 delivers the optimal activity and selectivity for CH₄, together with good stability, much better than those of a physical-mixture counterpart and most reported Cu-based perovskite oxides. Moreover, La₂CuO₄/(CaO)_0.8 stands out as one of the most effective Cu-based catalysts for CH₄ electrosynthesis, achieving a high CH₄ selectivity of 77.6% at 300 mA cm^–2. Our experiments and theoretical calculations highlight the significant role of self-assembly-induced strong interfacial interactions in promoting *CO adsorption/hydrogenation, intensifying resistance to structural degradation, and consequently underpinning the achievement of such optimized performance.