Beyond Local Coordination: How Global Structure Engineers the Selectivity of Single Atom Catalysts for CO₂ Reduction

The local structure of the active center is generally believed to determine the catalytic performance, but this rule fails in many situations. One of the representative cases is carbon-based single-atom catalysts (SACs), where Ndoped carbon (NC) and phthalocyanine (Pc) substrates usually endow the same active center (MN₄) with different performance. Herein, we unveiled an intrinsic global-local interplay mechanism, in which global structural engineering, coupled with local-site sensitivity, determines the catalytic performance of SACs. Specifically, the similar local active sites yield comparable d-band centers and reaction thermodynamics, while the distinct global structures induce markedly different potentials of zero charge (PZC). This disparity leads to the varying electron accommodation capacity and interfacial water orientation, altering the reaction energetics. Moreover, the degree of this global effect critically depends on the sensitivity of the local charge of the active site to the global structural variation. As a result, Co SACs, with greater sensitivity than Fe and Ni SACs, exhibit completely opposite selectivity between CoNC and CoPc. Our work transcends the conventional local-site paradigm and highlights the important role of global structure, in concert with local sensitivity, in governing catalytic performance.