Boron-incorporation-mediated interfacial water orientation for boosting CO2 electroreduction to CH4

Precisely regulating interfacial water orientation to optimize proton supply and intermediate stabilization remains a critical challenge for efficient and selective electrochemical CO 2 reduction to CH 4 , a high-value energy carrier with complex eight-proton-coupled electron transfer kinetics. Herein, we address this challenge by developing a boron (B) incorporation strategy to engineer the interfacial water microenvironment of Cu-doped CeO 2 catalysts, where heteroatom B doping reorients interfacial water from an O-down to H-down configuration. The optimized 1.25BC-Cu catalyst achieves a maximum Faradaic efficiency (FE) of 74.9% for CH 4 at −1.7 V vs . reversible hydrogen electrode (RHE), accompanied by a high partial current density of −582.4 mA cm –2 , outperforming most previous CO 2 -to-CH 4 catalysts. This catalyst also exhibits exceptional long-term stability, with negligible current decay and well-retained CH 4 FE after 30 h of continuous electrolysis. Systematic experimental characterizations, including in-situ attenuated total reflection infrared spectroscopy, in-situ Raman spectroscopy, and electrochemical measurements, confirm that the H-down water alignment accelerates water dissociation for efficient *H generation and facilitates key CO 2 RR intermediates hydrogenation. Ab initio molecular dynamics and density functional theory calculations further reveal that B and Cu co-doping modulates the electronic structure of CeO 2 , upshifting the d -band center to enhance intermediate adsorption affinity, and reduces the free energy barrier of the rate-determining step for CH 4 formation. The B incorporation drives ordered H-down water arrangement, optimizing proton transfer kinetics and suppressing competitive side reactions. Our findings establish heteroatom-mediated interfacial water orientation as a pivotal design principle for tailoring CO 2 RR selectivity, providing a new avenue for the rational synthesis of high-performance electrocatalysts for efficient CO 2 methanation and energy storage.