Lattice Oxygen-Mediated Electrochemical Carbon Dioxide Reduction

Despite extensive studies on CO₂ electroreduction, the specific roles of lattice oxygen atoms and hydroxyl groups in the catalytic process are not yet well established. A critical challenge remains in determining whether these lattice oxygen species actively participate in the reaction pathway. Here, we report a lattice oxygen-mediated CO₂RR using Sn₃O₂(OH)₂ as a model catalyst for formate electrosynthesis. Employing operando ¹⁷O nuclear magnetic resonance (NMR) spectroscopy, we provide direct experimental evidence that formate products (HC¹⁷OO^– or HC¹⁷O¹⁷O^–) on isotopically labeled Sn₃¹⁷O₂(¹⁷OH)₂ originate from lattice ¹⁷O atoms via the lattice oxygen mechanism (LOM). Complementary density functional theory calculations further support the feasibility of a LOM route, which is fundamentally different from the conventional adsorbate evolution mechanism in the CO₂RR. The comprehensive operando XAFS analysis and XRD characterizations reveal that the Sn₃O₂(OH)₂ structure is stabilized by chelation with C₂O₄^2– ligands. These findings provide new mechanistic insights and design principles for developing highly active and stable oxide catalysts for CO₂RR via lattice oxygen participation.