A gradient Sn4+@Sn2+core@shell structure induced by a strong metal oxide–support interaction for enhanced CO2electroreduction

Oxidation states of Sn in tin oxides are hard to regulate due to the uncontrollable evolution during the electrochemical CO₂ reduction reaction (CO₂RR), thus limiting the adsorption capabilities and reaction kinetics. Herein, we propose a metal oxide-support interaction-mediated strategy to modify the electronic properties of tin oxides. A gradient Sn⁴⁺@Sn²⁺ core@shell structure was formed as a result of electron transfer from g-C₃N₄ to anchored SnO₂, unlike reduced graphene oxide (rGO)-supported SnO₂ with Sn⁴⁺-rich surfaces. Such unique structures were revealed by the depth profiles of X-ray photoelectron spectra, and they enhanced the adsorption and stabilization of the *CO₂˙^- intermediate and accelerated the reaction kinetics. Consequently, SnO₂/g-C₃N₄ delivered a faradaic efficiency of 95.1% for the C1 products at -1.06 V, exceeding those of SnO₂/rGO and most reported catalysts. Moreover, the performances were sustained for 70 h without obvious degradation. This work offers an alternative route to efficient catalyst design by combining oxidation state regulation and metal oxide-support interaction and contributes to the development of sustainable technologies for achieving carbon neutrality.