Visible-light-induced unbalanced charge on NiCoP/TiO2 sensitized system for rapid H2 generation from hydrolysis of ammonia borane

Abstract

Hydrolysis of ammonia borane is promising for instantaneously supplying hydrogen with moderate temperatures. Herein, we utilize NiCoP/TiO2 sensitized system to construct a highly unbalanced charge distribution for rapid H2 generation under visible light. The key point is optimizing the band structure to ensure electron injection from NiCoP to TiO2 because Ni2P and CoP cannot form this structure. Under visible light NiCoP is excited and inject electron to TiO2, generating a highly unbalanced but stable charge distribution. The positively and negatively charged NiCoP and TiO2 serve as activation sites for NH3BH3 and H2O, respectively. The H2 generation rate is increased from 0.18 mL/s in darkness to 0.36 mL/s under visible light, with Ea reduced from 52.76 kJ/mol to 25.89 kJ/mol. After modifying TiO2 with 2.5%Pt, the reaction is further increased to 0.55 mL/s. Full visible light can promote the reaction, with each photon trigger two NH3BH3 molecules for reaction.