Looping metal-support interaction in heterogeneous catalysts during redox reactions

Metal-support interfaces fundamentally govern the catalytic performance of heterogeneous systems through complex interactions. Here, utilizing operando transmission electron microscopy, we uncover a looping metal-support interaction in NiFe-Fe3O4 catalysts during the hydrogen oxidation reaction. At the NiFe-Fe3O4 interfaces, lattice oxygens react with NiFe-activated H atoms, gradually sacrificing themselves and resulting in dynamically migrating interfaces. Meanwhile, reduced iron atoms migrate to the {111} surface of Fe3O4 support and react with oxygen molecules. Consequently, the hydrogen oxidation reaction separates spatially on a single nanoparticle and is intrinsically coupled with the redox reaction of the Fe3O4 support through the dynamic migration of metal-support interfaces. Our work provides previously unidentified mechanistic insight into metal-support interactions and underscores the transformative potential of operando methodologies for studying atomic-scale dynamics. Metal–support interfaces play a crucial role in dictating the catalytic behavior of heterogeneous systems. Here, the authors reveal a unique looping metal–support interaction in NiFe–Fe₃O₄ catalysts, where spatially separated yet coupled redox cycles boost hydrogen oxidation, providing new insights for the design of efficient heterogeneous catalysts.