Inverse NiO_x-Ag Interface to Decouple Reactant Activation for Ag-Ni/SiO₂-Catalyzed Ester Hydrogenation

Achieving simultaneous high activity, selectivity, and stability in ester hydrogenation remains a persistent challenge, largely due to the competitive adsorption of reactants at active sites. Here, we introduce an inverse NiO_x-Ag interface as a general design platform to spatially decouple the activation of H₂ and ester, exemplified with dimethyl oxalate (DMO). The catalyst (Ag-Ni/SiO₂), synthesized via controlled partial reduction of Ni phyllosilicate followed by Ag deposition, features electron-rich Ag sites and electron-deficient interfacial Ni sites arising from interfacial electron transfer. Comprehensive characterizations reveal abundant NiO_x-Ag interfaces with modified coordination and electronic structures. In situ Fourier-transform infrared spectroscopy, temperature programmed desorption/surface reaction, and H₂-D₂ isotope exchange experiments demonstrate that H₂ is preferentially dissociated at Ag sites, while DMO adsorbs and activates on NiO_x sites, effectively mitigating competitive adsorption. Theoretical calculations confirm the cooperative nature of the interface, showing low barriers for H₂ dissociation and favorable desorption energetics for methyl glycolate (MG), suppressing over-hydrogenation. Accordingly, the Ag-Ni/SiO₂ catalyst delivers a turnover frequency of 944.4 h^-1 with ∼99% selectivity to MG over 500 h of continuous operation, among the highest reported for DMO hydrogenation. This work establishes interfacial inversion engineering as a versatile approach to optimize site complementarity in multi-step catalytic transformations.