Unveiling Ni-In alloy effect of Ni-based catalysts to boost hydrogen production in methanol steam reforming.

The advancement of highly efficient, selective catalysts stands as a pivotal challenge in methanol steam reforming (MSR) for hydrogen production. In conventional Ni-based catalysts, metallic Ni0 acts as the active site, synergizing with abundant surface oxygen vacancies of the oxide support and generating the intermediate *OCH₂ tends to directly decompose into CO, which further reacts with *H generated from H₂O activation to form CH₄, resulting in poor product selectivity. Herein, we propose a novel Ni/In₂O₃ catalyst that significantly enhances the selectivity of CO₂, increasing it from less than 10% to 90%. Comprehensive characterizations including XRD, XPS, H₂-TPR, UV-vis and TPSR reveal that, unlike conventional Ni0-based catalysts, the Ni/In₂O₃ catalyst forms a very active and selective Ni₂In₃ alloy phase that enables highly dispersed Ni species while endowing the catalyst with excellent capability for H₂O activation. Combined with further theoretical calculations, the catalytic reaction mechanisms of the CH₃OH and CH₃OH-H₂O systems on the catalyst surface are elucidated in detail. Density functional theory (DFT) calculations demonstrate that the d-p orbital hybridization in the Ni₂In₃ alloy effectively alters the electronic structure of Ni species and tunes the adsorption strength of reaction intermediates and balances the surface coverage of CH₂O* and *OH species, facilitating the critical HO-CH₂O* coupling step for CO₂ generation during methanol steam reforming and thereby improving the CO₂ selectivity of the Ni/In₂O₃ catalyst. The study presented in this work indicates that the formation of Ni-In active alloy phase may effectively overcome the inherent product selectivity issue of conventional Ni-based catalysts by regulating the surface coverage of the critical intermediate and therefore reaction pathway during methanol steam reforming.