First-principles energy band calculation and one step synthesis of N-doped BiPO₄

Highlights: • Nitrogen doped BiPO₄ was synthesized by one step hydrothermal method. • The valence and conduction bands, density of states and the band gap energy of BiPO₄ are calculated with first-principles. • The photocatalytic activity of BiPO₄ were enhanced after N-doping. • The reason for the enhancement of photocatalytic activity were investigated. - Abstract: N-doped BiPO₄ photocatalyst was synthesized by a simple one step hydrothermal method. The crystal structure, morphology, and photophysical properties of the samples were characterized by XRD, SEM, XPS, UV–Vis and Raman. The valence and conduction bands, density of states and the band gap energy of BiPO₄ are calculated with first-principles. The results showed that both BiPO₄ and N-doped BiPO₄ have same monoclinic structure. The substitution of O²⁻ by N³⁻ ions in BiPO₄ could not only cause the red-shift of the adsorption edge, but also change the morphology. The photocatalytic activity of BiPO₄ was enhanced about 50% under UV light irradiation when the molar ratio of N/Bi is 0.2, this can be ascribed to the N³⁻ introduced into BiPO₄ crystal lattice restrain the recombination of photogenerated electron–hole pairs. However, overdoping would decrease the photocatalytic activity of BiPO₄