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

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 molH2 (molmetal)^-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.