Photocatalytic properties of BiFeO 3 powders synthesized by mixture of CTAB and Glycine

Abstract

Highly pure BiFeO3 (BFO) powders were prepared by solution combustion synthesis method using cetyltrimethylammonium bromide (CTAB) and glycine as fuels at various fuel to oxidant (φ) ratios.Microstructural characteristics, morphology, optical properties, and thermal analysis were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), diffuse reflectance spectroscopy (DRS), and differential thermal/thermogravimetry (DTA/TGA), respectively. The combusted powders prepared at different fuel content contained some impurity phases such as Bi24Fe2O39 and Bi2Fe4O9. During the calcination of BFO powders at 600 °C for 1 hour, nearly pure BFO phase was produced. About 80% of methylene blue dye was photodegraded by combusted powders at φ=2 through 90 minutes of visible light irradiation.Developing simple, environmentally safe, and energy-efficient methods are of great interest to synthesize a pure BFO powder. Solution combustion synthesis (SCS) is a simple, relatively cheap, and fast chemical process to produce various nanomaterials [21]. A self-propagating exothermic reaction takes place between the mixture of metal nitrates and different organic fuels (e.g., glycine, citric acid, urea, etc.), releasing an enormous amount of gaseous products [20].Among organic fuels, glycine is an amino acid that facilitates the formation of metal ion complex in the solution owing to its carboxylic acid and amino groups at opposite ends of the molecule [22]. BFO has been synthesized by glycine fuel thru microwave-assisted solution combustion with some portion of impurity phases such as Bi 2 Fe 4 O 9 and Bi 24 Fe 2 O 39 [23]. Likewise, Cetyltrimethylammonium bromide (CTAB) is a cationic surfactant with high decomposition temperature that is extensively used to control particle shapes, size, and microstructure via minimizing the precursor's surface tension [24].Nevertheless, combining different fuels might be more effectual than that of individual fuels via improved control over the reaction temperature, the type, and the amount of gaseous products released. Therefore, in this project, glycine and CTAB were mixed in the uni-molar ratio to synthesize nearly pure and single-phase BFO. Experimental Procedure Synthesis RouteAnalytical grades Fe(NO 3 ) 3 .9H 2 O, Bi(NO 3 ) 2 .5H 2 O, CTAB [(C 16 H 33 )N(CH 3 ) 3 ]Br (> 99%), glycine (C 2 H 5 NO 2 ), were purchased from Merk Co. without any further purification. Whereby HNO 3 (68 wt %) was added to dissolve bismuth nitrate.The required amount of Bi(NO 3 ).5H 2 O and Fe(NO 3 ).9H 2 O, cetyltrimethylammonium bromide ([(C 16 H 33 )N(CH 3 ) 3 ]Br), and glycine (C 2 H 5 NO 2 ) were prepared by dissolving 15 mL of 3 mol L -1 of HNO 3 in various fuel to oxidant ratios of (φ = 0.5, 0.75, 1 and 2). H 2 O, CO 2 , Br 2 , and N 2 are assumed to be the gaseous products of combustion reaction where the type of gaseous products and adiabatic temperature are controlled by the fuel to oxidant ratio (φ).