Confinement-stabilized Cu0-Cu+ redox pair on silica and its catalytic role in Water–Gas Shift Reaction

Abstract

The construction and stabilization of Cu–O–Si interfaces in copper-based catalysts remain critical yet challenging for the water-gas shift reaction (WGSR), as conventional strategies fail to mitigate copper nanoparticle (NP) aggregation and interfacial instability. This study innovatively proposes a spatial confinement strategy by anchoring Cu NPs inside (Cu_in/SBA-15) or outside (Cu_out/SBA-15) the mesoporous channels of SBA-15, leveraging nanoscale confinement to optimize Cu–O–Si interfaces. The confined Cuin/SBA-15 catalyst demonstrated exceptional WGSR performance, achieving a reaction rate of 5.4 μmol_CO·g_cat⁻¹·s⁻¹, significantly surpassing conventional Cu/SBA-15 (3.1 μmol_CO·g_cat⁻¹·s⁻¹) and surface-loaded Cu_out/SBA-15 (2.8 μmol_CO·g_cat⁻¹·s⁻¹), along with remarkable stability. This enhancement originates from the SBA-15 channels enabling the in situ formation of stable Cu–O–Si interfaces, which regulate the dynamic equilibrium between Cu⁰ (active for H₂O dissociation) and Cu⁺ (critical for CO adsorption) species. In situ studies revealed their synergistic dynamic interconversion during WGSR, while domain confinement effects suppressed sintering by maintaining interfacial integrity. Kinetic and mechanistic analyses further identified the associative pathway, with HCOO* intermediate dissociation as the rate-determining step, facilitated by the stabilized Cu–O–Si interfaces. By resolving interfacial instability through confinement engineering, this work provides a paradigm for designing robust Cu-based catalysts, advancing both fundamental understanding and practical applications in WGSR and related heterogeneous catalysis.