Photocatalytic reduction of nitrate pollutants by novel Z-scheme ZnSe/BiVO4 heterostructures with high N2 selectivity

Eliminating nitrate pollutants in water efficiently and environmentally friendly has attracted widespread attention. As a promising technology to solve problems of environmental pollution and energy shortage, photocatalysis also displayed great potential in nitrate removal. In this work, a novel Z-scheme ZnSe/BiVO4 heterostructures were synthesized by in-situ growth of ZnSe nanospheres on BiVO4, and employed for photocatalytic reduction of nitrate in water. Experiments demonstrated that ZnSe/BiVO4 composites obtained improved photocatalytic activity compared with pristine ZnSe and BiVO4, and an optimal performance with nitrate removal rate as 89.84% and N2 selectivity as 91.03% in 50 min was achieved when initial nitrate was 100 mgN/L. The enhancements may be due to the boosted light harvesting capability and stronger redox ability of photogenerated carriers provided by Z-scheme ZnSe/BiVO4 heterostructures. Moreover, HCOOH played a better role as hole scavenger than CH3COOH and C2H5OH. The HCOOH dosage and initial solution pH greatly affected the photocatalytic removal of nitrate. Effects of impurity anions in water such as Cl−, SO42− and CO32− on nitrate removal were also investigated. The charge transfer pathway as well as photocatalytic mechanism for nitrate removal over ZnSe/BiVO4 heterostructures were proposed at the end.