N-p heterojunction composites Bi20TiO32-Bi2S3: Fabrication and efficient photocatalytic NO removal.

To efficiently remove nitrogen oxides at ppb level, a series of Bi20TiO32-Bi2S3 (BBS) composites were successfully crafted for the first time through a one-pot anion-exchange protocol and systematically characterized. It was confirmed that the in-situ grown Bi2S3 phase was anchored on surface of Bi20TiO32 and n-p heterojunction structures were established. The combination of high visible-adsorption Bi2S3 and formation of n-p heterojunction composites simultaneously strengthened the visible light harvesting, accelerated transfer and spatial segregation of charge carriers, and enriched the generation of oxidative species ·O2- and 1O2. Under visible irradiation, these as-synthesized BBS composites exhibited the significantly improved NO removal efficiency. In particular, the best candidate BBS-6 exhibited the highest NO removal efficiency of 35.4 % and the largest apparent rate constant (Kapp) of around 0.42 min-1, which were 2.36 and 2.64 times those of pristine Bi20TiO32, respectively. Besides, it possessed the lowest NO2 selectivity of 4.83 % and delivered the highest DeNOx index of 81.91 among all tested samples. This study provides valuable insights into the design and development of vulcanized Bi20TiO32 composites for effective NO removal at ppb levels under visible light irradiation.