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Multi-proton-coupled electron transfer, multitudinous intermediates, and unavoidable competing hydrogen evolution reaction during CO2 electroreduction make it tricky to control high selectivity for specific products. Here, we present spatial confinement of Fe single atoms (FeN2S2) by adjacent FeS clusters (Fe4S4) to orientate the transition of CO2 adsorption configuration from C,O-side to O-end, which triggers a shift of activated CO2 from first-step protonation to C–C coupling, thus switching the target product from HCOOH in high Faraday efficiency (FE: 90.6%) on FeN2S2 to CH3COOH (FE: 82.3%) on Fe4S4/FeN2S2. The adsorption strength of *OCHO upon the solitary FeN2S2 site is linearly related to the coordination number of Fe–S, with HCOOH predominantly produced over single-atom FeN2S2 (ortho-substituted S atoms). Fe4S4 cluster functions as a switch for a specific reduction product, which can not only optimize the spatial and electronic structure of the neighboring FeN2S2 but also impel complete reduction of CO2 to the hydrocarbon intermediate *CH3, followed by coupling of CO2* and *CH3 via the single-atom cluster synergistic catalysis of Fe4S4/FeN2S2. This spatial confinement strategy provides a new avenue to modulate the reactant adsorption model for desirable reaction pathways, with potential applications in diverse multistep electrochemical processes of controlled selectivity.
Wang et al. (Wed,) studied this question.