Photocatalytic dehydrogenation of ammonia borane over Ti3C2/MOF-supported Pd-doped Co nanoparticles

Abstract

Hydrogen storage in chemicals is regarded as one of the sustainable techniques for tackling the energy-related challenges. However, hydrogen production from ammonia borane (NH₃BH₃, AB) is restricted by the inherent activity of metallic catalysts, which may be boosted by light irradiation. Herein, Pd-doped Co nanoparticles (NPs) were incorporated into a Zr-MOF composite composed of MXene-derived Ti₃C₂ nanosheets and UiO-66-NH₂ (denoted as TUNS) by a double-solvent approach, obtaining a CoPd@TUNS composite. The optimized Co₃₀Pd@TUNS composite exhibited outstanding catalytic activity for the complete dehydrogenation of AB within 0.6 min under 300 W Xe lamp light, with a high turnover frequency of 130.37 mol_H2 (mol_metal)⁻¹ min⁻¹ at 298 K. The activity of Co₃₀Pd@TUNS increased 10-fold under light irradiation as compared to that in the dark. For photocatalytic dehydrogenation, Co₃₀Pd@TUNS was more active than Co₃₀Pd@UiO-66-NH₂ and Co₃₀Pd/Ti₃C₂. Its excellent performance might be attributed to multiple factors including the photo-harvesting MOF generating electron–hole pairs, Ti₃C₂ nanosheets promoting the charge separation, and the Schottky effect facilitating electron migration to metal NPs for activating the substrate via an electron-deficient BH₃ moiety, along with the attack of photogenerated hydroxyl radicals and water molecules. Moreover, the kinetic study manifested that AB dehydrogenation is a zero-order reaction with regard to the substrate. The great stability and recyclability of Co₃₀Pd@TUNS was also confirmed after 5 runs. This study would widen a pathway for the design of an efficient MOF-based catalyst for hydrogen generation in the energy-related field.