The Polymerization Effect on Synthesis and Visible-Light Photocatalytic Properties of Low-Temperature β-BiNbO4 Using Nb-Citrate Precursor

Low-temperature beta-BiNbO4 powders (denoted as Low-beta) were prepared by citrate and Pechini methods using homemade water-soluble niobium precursors. The addition of ethylene glycol and the resultant polymerization effect on the synthesis and visible-light photocatalytic performance of beta-BiNbO4 powders were fully investigated. The polymerization effect is beneficial to lower the phase formation temperature and obtain smaller particle catalysts. Both methods can synthesize catalysts with excellent performance of visible-light degradation of methyl violet (MV). The Low-beta BiNbO4 powder prepared by citrate method shows better degradation rate of about 1 h to decompose 80 % of MV and also displays good photocatalytic stability. The photodegradation of MV under the visible-light irradiation followed the pseudo-first-order kinetics according to the Langmuir-Hinshelwood model, and the obtained first-order rate constant and half-time are 2.85 x 10(-2) min(-1) and 24.3 min, respectively. The better photocatalytic performance of BiNbO4 powders prepared by citrate method can be attributed to its smaller band gap and better crystallinity.