Improving the denitration performance and K-poisoning resistance of the V_2O_5-WO_3/TiO_2 catalyst by Ce^(4+) and Zr^(4+) co-doping

A series of V2O5‐WO3/TiO2‐ZrO2,V2O5‐WO3/TiO2‐CeO2,and V2O5‐WO3/TiO2‐CeO2‐ZrO2 catalysts were synthesized to improve the selective catalytic reduction(SCR)performance and the K‐poisoning resistance of a V2O5‐WO3/TiO2 catalyst.The physicochemical properties were investigated by using XRD,BET,NH3‐TPD,H2‐TPR,and XPS,and the catalytic performance and K‐poisoning resistance were evaluated via a NH3‐SCR model reaction.Ce^4+and Zr^4+co‐doping were found to enhance the conversion of NOx,and exhibit the best K‐poisoning resistance owing to the largest BET‐specific surface area,pore volume,and total acid site concentration,as well as the minimal effects on the surface acidity and redox ability from K poisoning.The V2O5‐WO3/TiO2‐CeO2‐ZrO2 catalyst also presents outstanding H2O+SO2 tolerance.Finally,the in situ DRIFTS reveals that the NH3‐SCR reaction over the V2O5‐WO3/TiO2‐CeO2‐ZrO2 catalyst follows an L‐H mechanism,and that K poisoning does not change the reaction mechanism.

Photoelectrocatalytic activity of immobilized Yb doped WO3 photocatalyst for degradation of methyl orange dye

Pure WOand Yb:WOthin films have been synthesized by spray pyrolysis technique. Effect of Yb doping concentration on photoelectrochemical, structural, morphological and optical properties of thin films are studied. X-ray diffraction analysis shows that all thin films are polycrystalline nature and exhibit monoclinic crystal structure. The 3 at% Yb:WOfilm shows superior photoelectrochemical（PEC） performance than that of pure WOfilm and it shows maximum photocurrent density（Iph= 1090 μA/cm） having onset potentials around +0.3 V/SCE in 0.01 M HClO. The photoelectrocatalytic process is more effective than that of the photocatalytic process for degradation of methyl orange（MO） dye. Yb doping in WOphotocatalyst is greatly effective to degrade MO dye. The enhancement in photoelectrocatalytic activity is mainly due to the suppressing the recombination rate of photogenerated electron-hole pairs. The mineralization of MO dye in aqueous solution is studied by measuring chemical oxygen demand（COD） values.

Fabrication of ion doped WO_3 photocatalysts through bulk and surface doping

Na＋doped WO3 nanowire photocatalysts were prepared by using post-treatment（surface doping） and in situ（bulk doping） doping methods. Photocatalytic degradation of Methyl Blue was tested under visible light irradiation, the results showed that 1 wt.% Na＋bulk-doped WO3 performed better, with higher photoactivity than surface-doped WO3. Photoelectrochemical characterization revealed the differences in the photocatalytic process for surface doping and bulk doping. Uniform bulk doping could generate more electron–hole pairs, while minimizing the chance of electron–hole recombination. Some bulk properties such as the bandgap, Fermi level and band position could also be adjusted by bulk doping, but not by surface doping.

Anomalous temperature effect of nonlinearity of WO_3 varistor doped with Al_2O_3

MAKAROV and Trontelj first reported the WO3-based low voltage varistor material doped with MnO2 and Na2CO3 in 1994. This material is worth further study because of its low threshold voltage （ 【 10 V/mm）. We have found that the doping of Co2O3 can obviously improve the nonlinearity of WO3-MnO2-Na2CO3 series with nonlinear coefficient α≈ 2,and a may be higher than 5 when the amount of Co2O3 is 1% （mole percentage）. However, the nonlinear characteristic almost vanished when 0.5% Al2O3 was doped into this system at room temperature, and Al2O3 showed very stable

WO^(3+)掺杂对纳米TiO_2薄膜可见光致亲水性的影响

用溶胶-凝胶法和浸渍-提拉工艺在载波片上制备了均匀、透明的WO3+掺杂的纳米TiO2薄膜。用XRD、紫外-可见分光光度计分析了样品的晶相和光吸收性能,研究了WO3+的掺杂、掺杂量及热处理温度对薄膜可见光致亲水性的影响,并考察了薄膜在停止光照后,其亲水性能的变化。结果表明,与纯TiO2薄膜相比,掺WO3+的TiO2薄膜对可见光的吸收有所增强,并有一定的红移现象,且在可见光照射下,亲水性能都有提高,WO3+的最佳掺杂量为3%(物质的量比);薄膜的最佳煅烧温度为773K;停止光照后,掺WO3+的TiO2薄膜亲水性能持续的更久。

三氧化钨纳米粒子的改性研究进展

三氧化钨(WO3)能被用作可见光响应光催化剂,但由于导带位置较低、在本体中光生电荷载流子复合几率较高等因素,导致其量子产率较低,从而制约了其实际应用。所以,需要对WO3进行改性以提高其光催化性能。结合近年来国内外相关文献,综述了WO3掺杂改性的研究现状,并对WO3基光催化材料的发展趋势进行了展望。

Synthesis and in-situ noble metal modification of WO3·0.33H2O nanorods from a tungsten-containing mineral for enhancing NH3 sensing performance

Ag-and Pt-doped WO3-0.33 H2O nanorods with high response and selectivity to NH3 were synthesized from a tungsten-containing mine ral of scheelite concentrate by a simple combined process,namely by a high pressure leaching method to obtain tungstate ions-containing leaching solution and followed by a hydrothermal method to prepare corresponding nanorods.The microstructure and NH3 sensing perfo rmance of the final products were investigated systematically.The microstructure characte rization showed that the as-prepared WO3-0.33 H2 O nanorods had a hexagonal crystal structure,and Ag and Pt nanoparticles were uniformly distributed in the WO3-0.33 H2O nano rods.Gas sensing measurements indicated that Ag and Pt nanopa rticles not only could obviously enhance NH3 sensing properties in terms of response,selectivity as well as response/recovery time,but also could reduce the optimal operating temperature at which the highest response was achieved.The highest responses of 22.4 and 47.6 for Agand Pt-doped WO3-0.33 H2O nanorods to 1000 ppm NH3 were obtained at 225 and 175℃,respectively,which were about four and eight folds higher than that of pure one at 250℃.The superior NH3 sensing properties are mainly ascribed to the catalytic activities of noble metals and the different work functions between noble metals and WO3-0.33 H2 O.