Sodium Aluminate as a Water-Soluble Interfacial Modifier Coupling High-Temperature CO2 Retention and Ni Stabilization in Methane Dry Reforming

Abstract

Dry reforming of methane (DRM) demands catalysts that simultaneously resist coking and sintering at high temperature. Here, we show that sodium aluminate (NaAlO2) acts as a highly effective interfacial modifier, creating a functional Ni−NaAlO2 metal−support contact that couples reaction-relevant CO2 retention with robust Ni stabilization. Temperature-programmed desorption reveals that NaAlO2 retains CO2-derived species up to 700 °C, driven by the strong basicity of its ionic Na−Al−O lattice, while structural analysis confirms strong interfacial metal−support coupling that preserves the size of metallic Ni. In situ spectroscopy reveals a bifunctional perimeter pathway under DRM conditions, where these CO2-derived oxygen-containing species hosted on NaAlO2 efficiently oxidize CHx intermediates generated on adjacent metallic Ni sites. These coupled interfacial functions enable stable, near-coke-free DRM operation with suppressed Ni sintering for 110 h on stream, drastically outperforming a reference Ni/Al2O3 catalyst that deactivates via severe sintering, coking, and reactor blockage within 24 h. Crucially, NaAlO2 dissolves in water and undergoes reversible hydration/dehydration, enabling uniform post-synthetic deposition onto pre-formed Ni catalysts via a simple aqueous impregnation−drying step. We demonstrate that this modular interface incorporation successfully upgrades both a commercial Ni reforming catalyst and a reference Ni/Al2O3 catalyst without rebuilding the parent catalyst structures, significantly improving their coke and sintering resistance. Overall, this work establishes NaAlO2 as a deployable interfacial modifier for coupled CO2 handling and metal stabilization in practical reforming applications.