Acid-modulated Ni/MCM-41 catalysts enhance metal–support interactions for efficient perhydro-N-ethylcarbazole-based hydrogen storage and effective impurity gas suppression

Abstract

The rational design of cost-effective catalysts with tailored metal–support interactions (MSIs) is pivotal for advancing liquid organic hydrogen carrier (LOHC) technologies. Herein, we report a novel strategy to modulate the acidity of Ni/MCM-41 catalysts by tuning Si/Al ratios, which enhances MSIs via the formation of Si–OH–Al Brønsted acid sites. Systematic characterization, including NH₃-TPD, in situ Py-FTIR and HRTEM, reveals that reduced Si/Al ratios strengthen Ni–MCM-41 interactions, leading to highly dispersed Ni nanoparticles (4 nm vs. 6 nm for pristine Ni/MCM-41). Combined with DFT calculations, this also improves the H₂ dissociation kinetics. The optimized Ni–30-MCM-41 catalyst delivers markedly enhanced performance, exhibiting 1.7-fold higher hydrogenation activity than unmodified Ni/MCM-41 and achieving full hydrogen storage capacity (5.8 wt%, 100%) within 120 min at 443 K. This catalyst achieves full hydrogen storage capacity, matching the conversion activity of a commercial 3 wt% Pd/Al₂O₃ catalyst under the same conditions. Crucially, the acid-modulated interface suppresses impurity gas generation (CH₄: <100 ppm vs. 400 ppm for Pd) by weakening C–C bond cleavage while maintaining high H₂ purity. This work establishes a structure–activity relationship between Brønsted acidity, MSI, and catalytic performance, offering a sustainable, noble metal-free paradigm for LOHC systems. The findings underscore the transformative potential of acidity-driven MSI engineering in designing next-generation catalysts for hydrogen energy applications.