Synergistic catalysis and Mn doping effects in Ni-based catalysts for directional hydrogen production from lignin supercritical water gasification

This work elucidated the support-dependent catalytic mechanisms of Ni-based catalysts and the promotional effects of Mn modification in lignin SCWG via ReaxFF MD simulations, aiming to guide catalyst design through comparative analysis of support properties, metal dispersion, adsorption behavior, and product selectivity. The Ni/γ-Al 2 O 3 catalyst exhibited the highest metal dispersion (33.3%) and strongest interfacial adsorption energy, resulting in optimal hydrogen yield and selectivity (73.54%). The synergistic effect between surface defects of γ-Al 2 O 3 and Ni active sites initiated a sequence of reactions: C α /C γ dihydroxylation, β-O-4 homolytic reaction, benzene ring-opening, and carbon chain shortening. Mn doping further optimizes performance via two routes: Ni-Mn/γ-Al 2 O 3 enhanced the hydrogen yield and selectivity by improving metal dispersion (to 45.0%) and optimizing C/H/O adsorption energy, while Ni/Mn-Al 2 O 3 promoted the hydrogenation of CO 2 to CH 4 by enhancing surface acidity and oxygen vacancy concentration. This work provides new insights into designing high-efficiency Ni-based catalysts for lignin gasification.