The performance improvement method of g-C3N4 based catalyst for hydrogen production from ammonia borane: A DFT investigation

In the study, based on the purpose of efficient catalytic AB for hydrogen production, the photochemical properties influence of metal(Ru, Ni) and nonmetal(B,P) elements doping on the g-C3N4 are studied systematacially. The design method of high performance bifunctional catalyst of photocatalysis and metal catalysis are provided. The results have proved that both non-metals B, P and metal Ru, Ni have an efficient regulatory effect on the band structure of g-C3N4, which make the band gap of the clean monolayer g-C3N4(001) decrease from 1.175 eV to 0.261eV(B-g-C3N4(001)) and 0.671eV(P-g-C3N4(001)), 0.164 eV(Ni-g-C3N4(001)) and 0.260 eV(Ru-gC3N4(001)), respectively. B element have the better modification effect compared with the P element. The reduction of band gap is attributed to the electronic orbit modification effect of impurity element B, P, Ni, Ru in g-C3N4. Ru metal doped g-C3N4 is reduces the barrier of O-H bond breakage of CH3OH(reduced from 4.551 eV to 1.530 eV), which is beneficial to the hydrogen-producing reaction of AB alcoholysis. The construction and design of a new bifunctional catalyst(photocatalysis and metal catalysis) RuNiB@g-C3N4 is an efficient route in catalyze AB for hydrogen production. The process of molecule NH3BH3, CH3OH and H2O adsorbed on the B-gC3N4 are exothermic process, the adsorption energy are -1.562 eV, -1.392 eV and -1.443 eV, respectively. AB is preferentially adsorbed on the B-g-C3N4 catalyst, increasing the adsorption energy of CH3OH and H2O on B-gC3N4-based catalysts is beneficial to the hydrogen production from AB. The study provides a theoretical method for the research on the technology of the coupling of metal catalysis/photocatalysis ammonia borane to produce hydrogen.