Preparation of Ba<sub>3</sub>In<sub>2</sub>(OH)<sub>12 </sub> and its Photocatalytic Performance
Authors: Zhang Qin Ku , Yao Bing Hua 
Published: April 2016

Hydrogarnet Ba3In2(OH)12 was synthesized by hydrothermal method from raw materials Ba(NO3)2 and In(OH)3. The obtained sample was characterized by X-ray diffraction (XRD), scanning electron microscope(SEM), UV-visible diffuse reflectance spectroscopy (UV-vis DRS) and N2 adsorption-desorption isotherms (BET). Photocatalyitc activity was tested via rhodamine B(RhB) degradation as the modle pollutant. The influence of hydrothermal reaction temperature (T), hydrothermal reaction time (t), Ba/In molar ratio(Ba/In), and NaOH concentration(Cg) on the photocatalytic activity of Ba3In2(OH)12 were investigated. The results showed that the synthetic Ba3In2(OH)12 exhibited highest photocatalytic activity under the optimum hydrothermal reaction conditions of T=200°C, t=14 h, Ba/In=2:1 and Cg=7 mol/L. RhB can be completely mineralized by Ba3In2(OH)12 under 125 W mercury light irradiation for 3 hours.
There are many scholars and experts engaged in the research of various types of photocatalytic materials and applied in the degradation of environmental pollutants in the last 40 years. Such as, the oxide of In2O3[1], ZnO, TiO2 et al. The ternary oxide of indium, molybdate, tungstate and vanadate et al. New type quaternary metal oxide. In the past 20 years, indium-based semiconductor material were got rapid development in the field of display, laser, microwave devices, light-emitting diodes and photocatalyst because of which had good gas sensitivity, heat sensitivity, photosensitivity and other characteristics. CaIn2O4 was synthesized using self-propagating high-temperature sysnthesis method[2]. RhB can be absolutely mineralized under solar irradiation for 2 hours. The g-C3N4/CaIn2O4 composite was synthesized using facile solvothermal method[3]. The g-C3N4/CaIn2O4 composite reached a high H2 evolution rate of 62.5 μmol/h from CH3OH/ H2O solution when the content of grapheme was 1wt%. Furthermore, the 1wt% g-C3N4/CaIn2O4 composite did not show deactivation for H2 evolution for longer than 32 h. The core-shell like composite In2O3@Ba2In2O5 was synthesized via chemical impregnation method with sample calcination[4]. It degraded 100% of the MB in 30 min compared with P-25, which degraded 100% of the MB in 120 min. C-CdIn2O4 nanoparticle was synthesized by sol-gel templating method[5]. Natural sunlight illumination experiments showed the H2 evolution rate of C-CdIn2O4 was 17 μmol/h as compared to 2.1 μmol/h for the Pt:TiO2. Hydrogarnet Ba3In2(OH)12 was first described by Kwestroo et al in 1977, who used the prolonged refluxing of BaCl2 and In2O3 in 12 mol/L NaOH at 110°C[6]. The pure Ba3In2(OH)12 was prepared by first preparing pure Ba3In2O6 by prolonged reaction of stoichiometric amounts of BaCO3 and In2O3 at 1300 °C. Then, the pure Ba3In2O6 was reacted with 12 mol/L NaOH at 85 °C for 12 hours under a pure nitrogen atmosphere[7]. Hydrogarnet Ba3In2(OH)12 was synthesized by hydrothermal method, using In(OH)3, Ba(NO3)2 and NaOH. With RhB as a model degradation pollutant, the influence of hydrothermal reaction temperature, hydrothermal reaction time, Ba/In molar ratio and NaOH concentration on the photocatalytic activity of Ba3In2(OH)12 were investigated and the photocatalytic degradation mechanism of RhB were investigated. The results can provide references for the research and application of this material system in the future.