A modular calcination method to prepare modified N-doped TiO2 nanoparticle with high photocatalytic activity

•A modular calcination method to prepare high efficiently visible light driven photocatalyst is presented.•The effect of calcination order on photocatalytic activity is firstly reported.•The phenol is an important intermediate product in degradation process of benzene.•The paramagnetic centers existed in NV-TiO2 promote electrons transfer and migrate.

In this paper, a highly active modified N-doped TiO2 nanoparticle is prepared by a novel modular calcination method. The combination among ammonia, hydrogen, air and vacuum module is investigated comprehensively. Moreover, the effect of calcination order on photocatalytic activity is also studied. The photocatalytic property of sample annealed in ammonia firstly is better than that of the sample annealed in ammonia last. NV-TiO2 sample which is prepared by combination between ammonia and vacuum module possesses the highest photocatalytic activity towards benzene. The photodegradation result shows that 300 ppm benzene can be decomposed completely during four hour visible light illumination. The excellent photocatalytic performance is attributed to the improvement of light harvesting, charge separation and increased surface electron scavenger, simultaneously. Besides, the photocatalytic degradation reaction path of benzene demonstrates that phenol is an important intermediate product. The faster decomposition of phenol is corresponded to higher photocatalytic reaction rate. In fact, the effect of calcination order on the photocatalytic activity is embodied in differences of the amount of oxygen vacancy and surface cleanliness. These findings aid us to prepare highly efficient visible light active photocatalyst by using a simple method and deepen the understanding on the mechanism of decomposing benzene.

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