Highly efficient and selective NO photocatalytic abatement by tuning charge separation in multi-walled carbon nanotubes and Bi2WO6 microsphere heterojunction

Abstract

Carbon nanotubes can be used as good electron acceptors in heterojunctions. We designed a heterojunction structure of Bi2WO6 microspheres containing multi-walled carbon nanotubes (CNTs) to achieve highly efficient and selective photocatalytic NO oxidation. The heterojunctions CNTs/Bi2WO6 were synthesized successfully through using hydrothermal method, which was confirmed by SEM, TEM, Raman spectroscopy and other characterizations. Compared to the photocatalytic NO conversion efficiency of pure Bi2WO6, the NO conversion efficiency of CNTs/Bi2WO6 composite samples can reach 40% more than twice that of pure Bi2WO6 samples. More than 80% of the products were nitrate, just a little products were NO2, indicating that heterojunctions promoted the deep oxidation of NO and achieved highly selective NO oxidation in particularly. This promising performance is attributed to a unique mechanism. The designed unique structure stimulates the segregate of photo-generated electrons and holes effectively, enabling their respective participation in the production of ‧O2− and ‧OH intermediate species, which leads to effective NO oxidation. Among all the different mass ratios of CNTs/Bi2WO6 samples, the composite photocatalyst containing 1wt% CNTs/Bi2WO6 exhibited the best NO conversion efficiency and the highest selectivity. This work delineates a unique strategy for constructing a Bi2WO6-based heterojunction catalyst, and showcasing its effectiveness in NOX abatement applications.