Photocatalytic degradation of atrazine by boron-doped TiO₂ with a tunable rutile/anatase ratio

Atrazine is a widely used herbicide and a typical toxic pollutant. TiO₂-mediated photocatalysis is an efficient way to degrade such a refractory contaminate. In a photocatalyic process, great charge separation and efficient interparticle electron transfer are highly desired and are usually achieved through element doping and phase-junction optimization. However, in the traditional methods for synthesizing phase-junction TiO₂, high phase transition temperature and appropriate adjustors are always needed. In this work, boron-doped (B-doped) TiO₂ with a tunable anatase/rutile ratio is successfully synthesized for efficient atrazine degradation by using a simple one-step calcination method, which is conducted below phase transition temperature with as-prepared Ti and B mixture as a precursor. The formation of the surface-phase junctions between anatase and rutile nanoparticles enables effective interparticle electron transfer and results in more efficient charge separation. Also, the B-doping serves as charge traps, which are able to mediate oxidative electron transfer. The prepared B-doped TiO₂ exhibits a higher photocatalytic activity for the degradation of atrazine, with a reaction rate of 4 times faster than that of the non-doped counterpart. The photogenerated reactive species and degradation intermediates of atrazine are identified, and the photocatalytic atrazine degradation mechanism is elucidated. This study provides a new approach to prepare phase-junction photocatalysts and demonstrates that the anatase/rutile ratio can be tuned by doping element. Such a "killing two birds with one arrow" strategy could be extended for preparing other photocatalysts for the degradation of various pollutants.