Hydrothermal Synthesis of Li₉Fe₃(P₂O₇)₃(PO₄)₂ Nanoparticles and Their Photocatalytic Properties under Visible-Light Illumination

A visible-light-driven photocatalyst, Li(9)Fe(3)(P(2)O(7))(3)(PO(4))(2), prepared by a hydrothermal method was studied. The as-prepared catalyst exhibited efficient photocatalytic activity in the degradation of methylene blue (MB) under visible-light irradiation (lambda > 400 nm). Besides decoloring, the decomposition of phenol was also observed, further demonstrating the photocatalytic performance of Li(9)Fe(3)(P(2)O(7))(3)(PO(4))(2). It was found that hexadecyltrimethylammonium bromide (CTAB) affected the geometry, crystallinity, optical property, surface area, and photocatalytic activity of the material significantly. The sample obtained with CTAB addition during synthesis procedure showed the higher photocatalytic activity. 70% of MB could be photodegraded under visible-light irradiation after 3 h, showing the excellent photocatalytic activity of Li(9)Fe(3)(P(2)O(7))(3)(PO(4))(2). Furthermore, with I(-) as electron donor, 19 micromol/g of hydrogen was photocatalytically evolved from aqueous solutions after 5 h. According to experimental results, a possible photocatalytic mechanism of Li(9)Fe(3)(P(2)O(7))(3)(PO(4))(2) was proposed.