Engineering Migration Pathway for Effective Separation of Photogenerated Carriers on Multicomponent Heterojunctions Coated with Nitrogen-Doped Carbon.

Abstract

Multicomponent NiTiO3 /A-TiO2 /R-TiO2 photocatalysts coated with nitrogen-doped carbon (N-C/NiTiO3 /A-TiO2 /R-TiO2 ) for efficient H2 production were fabricated by directly pyrolyzing NH2 -MIL-125(Ni/Ti) metal-organic framework microrods. Owing to the synergistic effect of the N-doped carbon coating layer and multicomponent heterojunctions, the H2 production rate of N-C/NiTiO3 /A-TiO2 /R-TiO2 was even higher than that of its Pt-containing counterpart (Pt/NiTiO3 /A-TiO2 /R-TiO2 ). N-C/NiTiO3 /A-TiO2 and N-C/NiTiO3 /R-TiO2 as control photocatalysts were also prepared by simply adjusting the calcination temperature of NH2 -MIL-125(Ni/Ti) in air atmosphere. The H2 production rate followed the order of N-C/NiTiO3 /A-TiO2 /R-TiO2 >N-C/NiTiO3 /A-TiO2 >N-C/NiTiO3 >R-TiO2 , which indicates that the multicomponent heterojunction plays a key role in photocatalytic H2 generation. The mechanism for the influence of the multicomponent heterojunction on photocatalytic activity was investigated in combination with molecular simulations, which showed that N-C/NiTiO3 /A-TiO2 /R-TiO2 has a so-called double type II heterojunction providing a perfect step-by-step migration pathway for effective separation of photogenerated electrons and holes. This work presents a simple and effective method for synthesizing efficient multicomponent photocatalysts.