A comparative study of physicochemical and photocatalytic properties of visible light responsive Fe,Gd and P single and tri-doped TiO2 nanomaterials

High performance Fe-Gd-P tri-doped TiO_2 nanoparticles(1 at% for each dopant) were successfully synthesized by a modified sol-gel method. Various analytical and spectroscopic techniques were carried out to determine the physicochemical properties of the prepared samples, including XRD, EDX, FESEM,BET, FTIR, XPS, PL, EIS and UV-Vis diffuse reflectance spectroscopy. The photocatalytic activities of prepared samples were evaluated by photo degradation of methyl orange(MO) and 4-chlorophenol(4-CP) as model pollutants under visible light irradiation. Effects of each dopant on different properties of TiO_2 nanoparticles were investigated. Results show that Gd and P doping enhances TiO2 surface textural properties by forming Ti-O-Gd and Ti-O-P bonds. It is found that Gd plays a superior role in increasing oxygen vacancies and organic species on TiO_2 surface. Gd doping also facilitates transferring of the photo-induced charge carriers to the surface adsorbed species. The enhanced electronic band structure and visible light response, as well as high electron lifetime of Fe-Gd-P tri-doped sample is mainly attributed to Fe and Gd doping. The tri-doped TiO_2 with rate constant of k_(app)= 1.28 × 10~(-2) min~(-1) for MO and k_(app) = 0.94 × 10~(-2) min~(-1) for 4-CP, shows the highest photodegradation rate among all samples including undoped and single doped samples. The improved photocatalytic performance of Fe-Gd-P tridoped TiO_2 is due to the synergistic effect of enhanced surface chemistry and textural properties,increased number of surface adsorbed hydroxyl groups and organic species, improved visible light absorption, increased lifetime of the photo-induced electron/hole pairs and boosted interfacial charge transfer.     

Enhanced photocatalytic activities of Nd-doped TiO_2 under visible light using a facile sol-gel method

Titanium dioxide nanoparticles modified with neodymium in the range of 1 mol% to 5 mol% were prepared with template-free sol-gel method.The structures of obtained samples were characterized by X-ray powder diffraction analysis.X-ray photoelectron spectroscopy,scanning electron microscopy,transmission electron microscopy and diffuse reflectance spectroscopy.The photocatalytic activity of the obtained samples was evaluated by photodegradation of methyl orange in aqueous solution under ultraviolet-visible(λ 350 nm) and visible(λ 420 nm) irradiation.The experimental results show that the 1 mol% Nd-doped TiO_2 exhibits the highest photocatalytic activity,of which the degradation can reach to 96.5% under visible irradiation.According to the XRD results,the pristine samples are combined with anatase TiO_2 and rutile TiO_2.while the Nd-doped TiO_2 samples are anatase TiO_2 only.This transformation has made an obvious promotion of photocatalyst activity after modification.     

Synthesis and characterization of tungsten and barium co-doped La_2Mo_2O_9 by sol-gel process for solid oxide fuel cells

Herein, we demonstrate the synthesis of W and Ba co-doped La_2Mo_2O_9(LBMWO) nanocrystalline powder by a sol-gel process. In all the compositions have general formulae La_(1.9)Ba_(0.1)Mo_(2-x)W_xO_(8.95)(x = 0-0.40). The crystal structure, microstructure and conductivity of LBMWO were characterized by X-ray diffraction, scanning electron microscopy and electrical impedance spectroscopy. In addition, the thermal and decomposition properties of the LBMWO gel were analyzed by differential scanning calorimetry-thermogravimetric. The results reveal that all LBMWO powders calcined at 700 ℃ have a cubic structure;the average crystallite size is about 48 nm. The unit cell parameter of LBMWO powders increases with increase in W content. The as-synthesized nanocrystalline LBMWO samples exhibit excellent sinterability and a relatively lower sintering temperature of 900 ℃. A high relative density of -96% is achieved after sintering at 900 ℃ which is in good agreeme nt with the re sults of the SEM. Moreover, W and Ba codoping suppresses the phase transition and effectively stabilizes the β-phase at low temperature. At the same time,La_(1.9)Ba_(0.1)Mo_(1.85)W_(0.15)O_(8.95) exhibits high ionic conductivity, 3.07 x 10~(-2) S/cm at 800 ℃. It is therefore concluded that co-doping can improve the properties of La_2MO_2O_9 electrolytes.     

Preparation of CeO2-TiO2/SiO2 and Its Removal Properties for Fluoride Ion

Ｈｙｄｒｏｕｓｏｘｉｄｅｓｏｆｓｏｍｅｍｅｔａｌｓ，ｓｕｃｈａｓＣｅ，Ｎｂ，Ｌａ，Ｔｉｅｔｃ．，ｓｈｏｗｅｘｃｅｌｅｎｔａｄｓｏｒｐｔｉｏｎｃａｐａｃｉｔｉｅｓａｎｄｓｅｌｅｃｔｉｖｉｔｙｆｏｒＦ－［１］，ｗｈｉｃｈｍａｋｅｓｉｔｐｏｓｉｂｌｅｔｏｕ...     

Molten salt synthesis of Z-scheme CeO2/C3N4 photocatalysts with excellent properties for removal of organic pollutants: Characterization,kinetics and mechanisms

In this work,we firstly synthesized a CeO₂/C₃N₄ photocatalyst with Z-scheme heterojunction by a facile LiC-KCI molten salt method.The synthesized catalyst has an excellent quality for removing organic pollution of dyes and antibiotics in wastewater.As an example,the CeCN-1:5 prepared with a mass ratio of Ce₂(CO₃)₃·xH₂O:C₃H₃N₆=1:5 exhibits a methylene blue(MB) removal capacity of 100%with...     

A novel n-CeO_2/n-CdO heterojunction nanocomposite for enhanced photodegradation of organic pollutants under visible light irradiation

In this study,a series of novel visible light driven n-CeO_2/n-CdO heterojunction(CeO_2/CdO)nanoco mposites we re successfully fabricated by simple ultrasonication method.Several characte rization tools including X-ray diffraction(XRD),scanning electro n microscopy(SEM),transmission electron microscopy(TEM)and UV-vis diffuse reflectance spectroscopy(UV-DRS),etc.,were utilized to investigate the physicochemical properties of the catalyst and confirm the formation of heterojunction.Under visible light irradiations,the photocatalytic activities of the as-prepared CeO_2/CdO nanocomposites were evaluated by degrading of Congo red(CR)and Rhodamine B(RhB)solutions.As a result,the CeO_2/CdO(mass percentage ratio 1:3)nanocomposite displays remarkable performance for CR and RhB degradation.The enhancement in the photocatalytic performance of CeO_2/CdO(1:3)nanocomposite can be attributed not only to the strong visible-light absorption region,separating the photogenerated electronhole pairs but also to the formation of n-n type heterojunction.The results also indicate that the CeO_2/CdO(1:3)nanocomposite has good stabilization and high reusability.In addition,the mechanism is proposed for the coupled semiconductors and possible reasons for the enhancement of visible-light photocatalytic efficiency are also discussed.This work can provide a new gateway to fabricate visible photocatalysts and promising candidate catalysts for poisonous wastewater treatment in the near future.     

Gd2O3 nanoparticles modified g-C3N4 with enhanced photocatalysis activity for degradation of organic pollutants

Gd₂O₃ nanoparticles modified g-C₃N₄ photocatalytic composites were synthesized by a simple one-step hydrothermal method. The structure, morphology, optical properties of the prepared photocatalyst were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), field emission transmission electron microscopy (FETEM) and X-ray photoelectron spectroscopy (XPS). The result demonstrates that gadolinium is mainly dispersed on the surface of g-C₃N₄ in the form of Gd₂O₃, and does not destroy the lattice structure of g-C₃N₄. Besides, the gadolinium can cause the red shift of the absorption edge of light, narrow the band gap, and increase the separation efficiency of the photogenerated electron and hole of g-C₃N₄. Especially, the specific surface area of g-C₃N₄ can be significantly increased. Furthermore, g-C₃N₄/Gd-0.05 displays the highest photodegradation performance when it is used for degradation of methyl orange (MO), methylene blue (MB) and Rhodamine B (RhB). The photodegradation rate of g-C₃N₄/Gd-0.05 composites is 72.4% for MO, 95.5% for RhB, 100% for MB after 120 min under visible light (λ > 420 nm) irradiation. Narrow band gap promotes the separation of photogenerated electron and hole, which enhances the photocatalytic activity of g-C₃N₄. It is noted that g-C₃N₄/Gd-0.05 exhibits excellent photocatalytic stability by the photocurrent and the cyclic photodegradation of MO.     

New insights into the role of vanadia species as active sites for selective catalytic reduction of NO with ammonia over VO_x/CeO_2 catalysts

A series of VO_x/CeO_2 catalysts we re synthesized via vanadia supported on ceria with different BET surface areas.The catalysts were employed to investigate the active sites for the selective catalytic reduction of NO with NH_3(NH3-SCR).The kinetic results show that VO_x/CeO_2 catalysts exhibit nearly constant apparent activation energies(E_a),indicating the same SCR reaction mechanism.The V-O-Ce bridging modes and oligomeric VO_x were identified and quantified by Raman,FT-IR and H_2-TPR.The amounts of the V-O-Ce bridging modes calculated by H_2-TPR are correlated to the NH_3-SCR intrinsic reaction rates.The turnover frequencies(TOFs) show a constant value at the same temperature,which were calculated based on the number of V-O-Ce bridging modes of VO_x/CeO_2 catalysts.Therefore,it can be concluded that the V-O-Ce bridging modes are the active sites of VO_x/CeO_2 catalysts for the NH3-SCR reaction.     

Understanding the role of tungsten on Pt/CeO2 for vinyl chloride catalytic combustion

Spherical CeO₂ synthesized by the hydrothermal process was used as support to prepare Pt/WO₃/CeO₂,and the effects of tungsten(W) contents on activity,stability and polychlorinated by-products were investigated to understand the role of W for vinyl chloride(VC) catalytic oxidation.The introduction of12 wt% W to Pt/CeO₂(P12 WC) exhibits the highest catalytic activity with 90% conversion of VC at 250℃,meanwhile the stability improves and the polychlorinat...