Investigation of the effect of ytterbium doping on photoluminescence and photocatalytic activity of Li4Ti5O12

This work reports the combined effect of the morphology and crystallization to investigate the role of Yb³⁺ as an additive in Li₄Ti₅O₁₂ crystals on its photocatalytic and photoluminescence (PL) properties. With the pure phase, the synthesized samples have a spherical morphology and spherical structure with good crystallinity and uniform particle size distribution. Li₄Ti₅O₁₂ doped with ytterbium (Yb³⁺), were obtained by a new optimized hydrothermal approach. The crystal properties and surface morphology of the synthesized compounds were examined by X-ray diffraction method and field emission scanning electron microscopy. Bond structures and surface areas were investigated by Fourier transform infrared spectroscopy and Brunauer-Emmett-Teller analyses. Finally, the excitation and emission spectra were obtained by a PL spectrophotometer. The PL results show that room-temperature PL of Yb³⁺ doped Li₄Ti₅O₁₂ phosphor has an emission peak at 710 nm which can be attributed to Li₄Ti₅O12 crystal defect emission. Moreover, it has been found that Yb doping resulted in enhancement of photocatalytic activity, evaluated by monitoring the degradation of methylene blue solution. Note that, 0.01% Yb doped lithium titania phosphor exhibited excellent photocatalytic activity.     

BiOBr/g-C3N4光催化剂的制备及其LED紫光光催化活性

以五水硝酸铋、溴化钾和三聚氰胺为原料,采用溶剂热法制备了摩尔比不同的BiOBr/g-C3N4复合光催化剂,并进行了XRD、SEM和DRS表征分析.以50 W LED紫光灯为光源,采用罗丹明B为目标降解物考察了制备样品的光催化性能.结果表明:摩尔比为1∶1的BiOBr/g-C3N4复合光催化剂的具有最优的光催化性能.机理实验结果表明:超氧自由基(O2·-)和空穴(h+)为BiOBr/g-C3N4复合光催化剂光催化过程最为主要的活性物种.     

定向转化策略创制氮氧化物光催化剂

太阳能高效转化与利用是解决能源和环境两大问题的理想途径,而提高窄禁带半导体的光催化活性是有效利用太阳能资源的重要策略。其中,氮氧化物在可见光区有较强的吸收,被认为是一种潜在的可见光区光催化材料。当前,氮氧化物主要通过热氮化获得,即氨气在1 173~1 373 K条件下持续通过氧化物10 h以上。由此制备的氮氧化物往往只暴露低活性晶面,且生成的大量还原态缺陷可作为光生电荷的复合中心,严重制约了其在光催化领域的广泛应用。为此,总结了一种定向转化策略创制高质量氮氧化物光催化材料。该策略通过选取含挥发组分的氧化物前驱体实现对氮氧化物缺陷和晶面的有效调控,为其在太阳能光催化领域中的广泛应用奠定基础。同时,此定向转化策略可拓展到其他材料体系,为开发高效光催化剂提供新思路。     

Zr掺杂g-C3N4光催化降解有机污染物

以盐酸胍为前驱体，硝酸锆为锆源，通过热聚合法制备了Zr掺杂的Zr/g-C3N4光催化剂。运用XRD、SEM、UV-Vis DRS、PL、XPS、BET等手段对催化剂的结构、形貌、光学性能进行了表征分析。结果表明：Zr掺杂改性的Zr/g-C3N4光催化剂拓宽了可见光的吸收，增大了比表面积，且降低了光生电子-空穴的复合率，具有较好的光催化活性。可见光照射下，在60 min内，5Zr/g-C3N4对罗丹明B（RhB）的光催化降解率达99.29%，光催化降解过程符合一级动力学方程，其速率常数k= 0.08647 min-1，是纯g-C3N4的8.3倍。捕获剂实验发现降解RhB的主要活性物种为超氧自由基，并推测了可能的反应机理。     

Gd~（3＋）掺杂SiO_2/TiO_2的制备及降解活性（英文）

采用溶胶-凝胶法制备Gd3＋掺杂SiO2/TiO2（Gd3＋-SiO2/TiO2,GST）。用X射线衍射（X-ray diffraction,XRD）仪、热重-差热分析仪、紫外-可见分光光度计（ultraviolet-visible spectrophotometry,UV-Vis）及X射线光电子分光仪（X-ray p...     

PW/MCM-41光催化性能研究

以浸渍法制备了负载型光催化剂PW/MCM-41,并对催化剂进行了表征,考察了催化剂在光催化模拟染料废水亚甲基蓝(MB)溶液降解反应中的催化活性.实验结果表明:催化剂负载量为30％、催化剂投加质量浓度为3.0g/L、MB溶液的初始质量浓度为10 mg/L、pH=5、光照时间100 min时,对亚甲基蓝降解率可达91％以上...     

一种新的光催化剂Bi_(36)Fe_2O_(57)的合成及光催化性能研究

报道了一种新型光催化剂Bi36Fe2O57的一种改进的共沉淀合成方法,对不同条件下制备的产物进行了X射线衍射物相分析、扫描电镜形貌分析和光催化性能测试。物相分析表明,缓冲溶液在制备单相Bi36Fe2O57粉体中起着重要作用。紫外可见漫反射谱图表明,Bi36Fe2O57粉体的禁带宽度约为2.06 eV,中性缓冲溶液条件下合成的Bi36Fe2O57产物结晶性好,在金卤灯下照射3 h,对甲基橙的降解率可达82.7%,在紫外灯下照射2.5 h降解率达到99.3%。     

两种负载膜对纳米Fe~(3+)/TiO_2光催化活性的影响

用溶胶-凝胶法制得的纳米Fe3+/TiO2分别以玻璃和琼脂糖为负载体,采用浸渍-提拉法制备Fe3+/TiO2玻璃负载膜,水热合成法制得Fe3+/TiO2琼脂糖凝胶负载膜,通过降解某制药厂的制药废水,探讨两种负载膜对纳米Fe3+/TiO2光催化活性的影响及用琼脂糖为载体的可行性。结果表明,两种负载膜中纳米Fe3+/TiO2的晶相不变,但琼脂糖凝胶负载膜中纳米Fe3+/TiO2粒子的团聚较少,且不易脱落,重复使用性能高,光催化活性明显较Fe3+/TiO2玻璃负载膜强,从而显示了琼脂糖为载体的可行性、优越性和实用性。     

Does photoelectrocatalysis by TiO2 work?

BACKGROUND: This paper examines TiO₂ photoelectrocatalysis (PEC), a process that increases the efficiency of TiO₂ photocatalysis (PC) by applying a potential to separate the UV‐generated charge carriers whose recombination typically limits photonic efficiencies of conventional photocatalysis. RESULTS: Four representative photoelectrocatalytic reactions, nitrophenol oxidation, oxalate degradation, E. coli inactivation and dye decolouration were considered. For all four, a small applied potential raised the rate of pollutant removal by TiO₂ electrodes. Because the improvements were probably insufficient to make PEC technologically viable except in niche applications, rates of pollutant removal by PEC and by PC using TiO₂ particle dispersions were directly compared. PEC rates were not significantly larger than rates of PC by dispersions. CONCLUSION: Discussions of the implications of these conclusions focus on whether PEC is currently limited by reactor design (irradiation geometry, or mass transfer) or by electrode materials. It is inferred that the performance of present electrodes is not limited significantly by mass transfer constraints. Since the choice of electrode materials (sol–gel or thermal electrodes) has been shown to influence PEC efficiency, recent results on titania nanotubes (TNT) are reviewed. It is concluded that the enhancement factors—the PEC:PC ratio—of TNT electrodes are no higher than those of conventional materials. Copyright © 2011 Society of Chemical Industry     

TiO2-SiO2复合薄膜光催化活性与亲水性关系的研究

采用溶胶凝胶法在载玻片表面制备了均匀透明的TiO2-SiO2超亲水性薄膜。利用XPS，XRD，lR等对光催化活性和亲水性关系进行了研究。结果表明：薄膜的亲水性与光催化活性协同作用是其保持自清洁的关键。添加SiO2后，复合氧化物中表面形成Lewis酸，薄膜表面吸附的羟基含量增多且稳定。在与有机物竞争吸附过程中，水优先吸附，可提高薄膜的超亲水性和光催化活性，有利于提高其自清洁性能。