The halogen atoms induced different oxygen vacancies in RbNa2B6O10X (X = Cl, Br) for the enhanced photo-dechlorination properties

Abstract

The halogen (X = Cl, Br) atom-substituted oxyhalide borate crystal materials RbNa2B6O10Cl (RNBC) and RbNa2B6O10Br (RNBB) with different oxygen vacancies were successfully prepared by high-temperature solid-phase method. Due to the Cl atom has a larger electronegative property can bring a greater deformation compared with Br atom, resulting in a larger oxygen vacancies concentration in the crystal. ESR tests also confirmed that the oxygen vacancy concentration of RNBC was higher than that of RNBB. The different alignment of B6O13 groups in two materials cause a non-central symmetric for RNBC and central symmetric for RNBB, this brought a built –in electric field existing in the RNBC which facilitate the electrons and holes separation when the light irradiation on the surface of the material. The photocatalytic activity of 2-CP under UV light irradiation showed that the degradation efficiency of RNBC was superior to RNBB, and the reaction rate constants of RNBC and RNBB were 0.1577 and 0.1257 min−1 respectively. Active radical experiments confirmed that in the photo-degradation of 2-CP, the O2– was the main active species and followed by e−, h+, OH.