Coordination Competition Couples Oxygen Vacancy‐Rich SnO x With Isolated Cu–N Sites for CO 2 ‐to‐formate Electroreduction

Abstract

ABSTRACT Selective CO 2 ‐to‐formate electroreduction requires oxygen‐deficient SnO x sites that stabilize O‐bound * OCHO intermediates while resisting cathodic over‐reduction. Here, we use a precursor‐level coordination competition strategy to construct an oxygen vacancy (O v )‐rich SnO x catalyst coupled with isolated Cu–N sites through controlled conversion of amino‐functionalized Cu/Sn metal‐organic frameworks. Competitive coordination of Cu and Sn with 2‐aminoterephthalic acid (H 2 BDC‐NH 2 ) is associated with altered precursor growth and a heterogeneous local environment, favoring the formation of defective SnO x domains during thermal conversion while enabling ligand‐derived nitrogen sites to anchor redistributed Cu species. Spectroscopic investigations reveal that the optimized Cu‐SnO x /NC catalyst contains abundant vacancy‐related SnO x environments and predominantly isolated Cu–N configurations, which are associated with stabilized O‐bound * OCHO intermediates and mitigated cathodic reconstruction of SnO x . Operando Raman spectroscopy further indicates persistent formate‐related intermediates and comparatively lower bicarbonate accumulation during CO 2 electroreduction. Consequently, Cu‐SnO x /NC achieves a formate Faradaic efficiency (FE) of 96% at −100 mA cm −2 and maintains efficiencies above 85% over a moderate current density range in both alkaline and neutral electrolytes. Half‐cell and full‐cell energy efficiencies (EE) of 65% and 54%, respectively, were achieved in the flow cell and membrane electrode assembly (MEA). This work provides a coordination‐competition strategy for durable high‐rate CO 2 electroreduction.