A Dual-Function Design: Carbon-Encapsulated Cu/Al2O3-ZnO for Highly Active and Stable Hydrogen Production via Methanol/Water Reforming

Abstract

Hydrogen (H2) is a sustainable and carbon-neutral energy alternative. Practical H2 production via aqueous-phase reforming of methanol (APRM) requires high-performance catalysts. Herein, we report the design of a Cu-guar gum/Al2O3-ZnO (Cu-GG/AZ) catalyst and elucidate its structure–performance relationship using a combination of complementary characterization methods. At 240 °C, the catalyst achieves a H2 production rate of 249.2 μmol/gcat/s with 99.92% H2 selectivity and < 0.10% CO selectivity, and maintains good stability over five hydrothermal cycles. High efficiency arises from carbon encapsulation, which stabilizes Cu+/Cu0 sites and enhances diffusion/adsorption through better interfacial wettability. The APRM mechanism is identified as methanol dehydrogenation (MD) coupled with the water-gas shift (WGS) reaction. Density functional theory (DFT) calculations reveal that graphitic carbon supported Cu/Al2O3-ZnO lowers the Gibbs free energy of the rate-determining step for both MD and WGS processes through enhanced electron modulation. Weakening *H2 adsorption (from –0.09 to 0.15 eV) boosts H2 release. A key oxygen-containing species (*OH) is enriched and adsorbed at Cu+/Cu0 sites, which facilitates the formation of *CH2O and *HCOOH and promotes *CO conversion.