High performance catalyst for metal catalysis coupled with photocatalysis and its catalytic ammonia borane methanolysis for hydrogen production

Abstract

In the study, the influence and mechanisms of metal and non-metal dopants on the photochemical properties of the semiconductor catalyst g-C3N4 are investigated. The results reveal that doping Ni, Ru, and B on g-C3N4 results in significant alterations to the energy band structure, the band gap value decreases to 0.78 eV (Ru@g-C3N4), 0.69 eV (Ni@g-C3N4), 0.5 eV (RuB@B-g-C3N4), and 0.1 eV (NiB@B-g-C3N4) from the original value of 1.139 eV. The doping of metal and non-metal atoms can significantly enhance the light absorption capability and photothermal conversion efficiency of B-g-C3N4. The mechanism of ammonia borane (AB) dehydrogenation follows the stepwise dehydrogenation principle. AB molecules adsorb onto the active metal centers, and with the assistance of the catalytic sites, CH3OH molecules activate and attack the B–N bond in AB molecules, leading to the initial breakage of the B–N bond, the interaction between O atoms in CH3OH and N atoms in AB continues, forming NH3BH2(OCH3). Interactions between H(B) and H(O) result in the production of H2, the energy barrier for this reaction is 34.14 kcal/mol. Compared to dark conditions, RuB@B-g-C3N4 exhibits higher catalytic activity under light irradiation, the reaction time from 9′20″ reduce to 8′. This shows that there is a synergistic effect between photocatalytic AB methanolysis and conventional metal catalyzed AB methanolysis in the RuB@B-g-C3N4 catalytic system. The study provides the novel way for the development of dual-function catalysts combining metal catalysis and photocatalysis through Ru and B modification of g-C3N4.