Janus Carbon Shells with Inner-Outer Functional Asymmetry Enables Local Proton Enrichment for Promoting CO 2 Methanation

Exploring non-copper-based electrocatalysts is important for CO2-to-CH4 electrosynthesis, as it reduces overreliance on copper and broadens the catalyst landscape. Herein, we report a strategy that enables CH4 formation on cobalt phthalocyanine (CoPc) by regulating the local reaction microenvironment through catalyst architecture. Hollow carbon nanospheres (HCNs) with uniform size and ultrathin carbon shells are synthesized and employed as supports for CoPc, forming "Janus carbon shells" with inner-outer functional asymmetry. The resulting CoPc/HCNs hybrid achieves a maximum CO2-to-CH4 selectivity of 15.1%, breaking the conventional CO-selective behavior of CoPc. Mechanistic studies show that the hollow carbon architecture induces local proton enrichment through an inner-outer surface synergy. The inner carbon surface promotes the hydrogen evolution reaction (HER) and supplies protons to the CoPc-active outer surface, creating a proton-rich environment that enables CO2 methanation. This work highlights the critical role of catalyst architecture in overcoming intrinsic selectivity limits of molecular catalysts.