硫掺杂二氧化钛光催化降解曙红Y溶液的研究

在sol-gel法制备TiO2的过程中引入过硫酸钾,制备具有可见光活性的硫掺杂二氧化钛,采用FTIR、SEM、XRD、粒度分析等手段进行表征,并以曙红Y溶液作为模型物在可见光作用下考察其光催化降解活性。结果表明:以可见光作光源,制备的硫掺杂二氧化钛能很好地降解曙红Y废水,在催化剂的投入量为0.8g/L,曙红Y溶液的初始浓度为10mg/L,光照时间为40min,pH=5条件下,曙红Y溶液的脱色率达97.16%。     

Ho掺杂纳米TiO2光催化性能研究

以钛酸四正丁酯为原料,采用溶胶-凝胶法制备了纯的和Ho掺杂的TiO_2纳米粒子,对样品进行了TG- DTA、XRD和UV-Vis吸收光谱分析,并以甲基橙的光脱色反应考察了样品的光催化性能。发现Ho的掺杂抑制了TiO_2粒径的长大,细化了晶粒;Ho掺入到TiO_2的晶格中,引起了晶格的畸变和膨胀;Ho的掺杂使TiO_2的吸收带边发生微小的蓝移,且在450nm和540nm光区附近产生吸收;适量Ho的掺杂可提高TiO_2的光催化性能,紫外光照下,Ho的掺杂量为0.3%时,光催化性能最佳;可见光下(波长>420nm),Ho掺杂的TiO_2呈现光催化活性,210min内甲基橙的脱色率可达21.6%。     

可见光响应负载型Er3+∶YAlO3/TiO2-SAC光催化剂的制备及其性能研究

为使TiO2能在可见光下发挥其于紫外激发的高光催化活性,且易于从处理废水中分离,采用溶胶-凝胶法将TiO2与掺杂稀土离子Er3+的上转换发光剂Er3+∶YAlO3结合再负载到球形活性炭(SAC)表面,制备可见光响应的负载型Er3+∶YAlO3/TiO2-SAC光催化剂并对其进行表征。以甲基橙为目标污染物,研究了制备的催化剂在可见光下催化活性,并探讨不同Er3+∶YAlO3/TiO2的负载方式、负载量等制备条件对光催化剂活性的影响。结果表明,结合方式为Er3+∶YAlO3/TiO2烧结后与SAC在乙醇介质中混合并进行30min磁力搅拌、以Er3+∶YAlO3/TiO2与SAC质量比为1∶4时制备的光催化剂活性最高,甲基橙的脱色率在240min可达97%以上。     

N掺杂的TiO2纳米管光催化剂的制备及其制氢特性

利用溶胶凝胶法,以钛酸四正丁酯为原料,尿素为氮源,合成N掺杂的Ti O2纳米颗粒(记作XNTi O2NP,其中X为合成时原料中N与Ti的原子比),并以此为原料利用微波法合成N掺杂的Ti O2纳米管(记作XNTi O2NT),并在相同铂载量、光照条件下评价催化剂的光催化制氢活性,研究不同掺杂比对催化剂活性的影响,找出最佳掺杂比。通过现代测试技术(DRS、TEM、XRD、XPS、ICP和EAI等),对催化剂的结构进行表征。实验结果表明:在不同N掺杂比的催化剂中,3NTi O2NT的产氢活性较高,其吸收边约为543.4 nm,在纯水和加牺牲剂(5%甲醇水溶液)的条件下的产氢速率为别为17.11μmol/(g·h)和415.40μmol/(g·h)。     

不同制备方法对Ag/AgCl光催化脱汞的影响

采用不同制备方法成功地制备了可见光催化剂Ag/AgCl,以VM-3000测汞仪为检测手段,在模拟烟气光催化反应器上考察了该可见光催化剂的单质汞(Hg0)脱除特性;采用N2吸附/脱附、扫描电子显微镜、X-射线衍射、X-射线光电子能谱以及紫外-可见漫反射光谱等表征手段分析了可见光催化剂的物理化学性质。表征分析表明:与改性的共沉淀法制备的Ag/AgCl相比,沉淀-光还原法制备地催化剂的比表面积、总孔容、AgCl衍射峰以及吸光度均有较大幅度的增强;脱汞实验表明荧光灯照射对可见光催化剂的脱汞活性起着重要的作用,在可见光照射下,沉淀-光还原法制备的催化剂表现出最好的脱汞活性,最大脱汞效率高达92%。     

微波合成载铂二氧化钛纳米管光催化剂及其光催化性能

以自制二氧化钛纳米颗粒为原料,利用微波反应器合成二氧化钛纳米管(Titania nanotubes,TNTs),然后利用微波助乙二醇还原法得到负载Pt的二氧化钛纳米管(Pt/TNTs)。利用高分辨率透射电镜(HRTEM)、X射线衍射(XRD)和紫外可见吸收光谱(UV-Vis)对该催化剂进行表征,并重点研究Pt/TNTs的光催化分解水性能。结果表明:Pt颗粒均匀分散在二氧化钛纳米管表面,微波助乙二醇还原法制备的Pt/TNTs较Pt负载TiO2颗粒在可见光区域表现出较强的吸收,并且其起始吸收带边发生明显红移,通过模拟太阳光分解纯水制氢实验可知,用微波助多元醇制备Pt改性的TiO2纳米管光催化剂具有更高催化剂活性,其在全波段下氢气产量优于Pt负载的TiO2纳米颗粒催化剂,且在可见光区能分解纯水产氢,产氢量为0.86L/(m2.h.g)。     

TiO2-xNx光催化剂的制备及其活性研究

在sol-gel法制备TiO2的过程中引入氨水进行水解,制备了具有可见光活性的TiO2-xNx催化剂,采用UV-Vis、BET、XPS等手段进行表征,以苯甲酸为模型污染物,氙灯为模拟太阳光源,评估了催化可见光催化活性.结果表明,随着焙烧温度的升高,TiO2-xNx的吸光特性增加,当温度超过350%后TiO2-xNx中的氮会在高温下被氧化掉,其吸光特性又降低;此时TiO2-xNx的吸收阈值为422nm,对应的禁带宽度为2.9eV;孔径分布在2.5～8.2nm之间,BET比表面积为139.3m2/g;经计算其x=0.0282,即TiO2-xNx可表示为Ti1.9718N0.0282;在入射波长分别为500nm和600nm时,TiO2-xNx对苯甲酸的去除率分别为6.5%和4.6%,相应的矿化率为3.2%和2.5%.     

B、Cr共掺杂K2La2Ti3O10光催化分解水制氢的性能

采用溶胶-凝胶法制备了B、Cr单独掺杂和共掺杂K2La2Ti3O10光催化剂,以CH3OH为牺牲试剂,500W氙灯辐射下进行光催化分解水反应,通过检测产氢量评价催化剂的催化性能,并通过XRD、UV-Vis漫反射吸收光谱(DRS)、XPS等技术对其进行表征.结果表明,Cr掺杂K2La2Ti3O10扩大了光谱吸收范围,吸收光红移至可见光区(λ＞400hm),光催化制氢活性显著提高.B、Cr共掺杂K2La2Ti3O10,共掺杂离子表现出良好的协同作用,进一步加强了对可见光的响应,降低了K2La2Ti3O10表面的晶格氧含量,有利于抑制光生电子-空穴对的再复合,从而大大提高了光催化分解水制氢活性.     

S掺杂ZnS纳米晶的水热合成及其可见光光催化活性

以硫代乙酰胺(TAA)和硝酸锌(Zn(NO_3)_2·6H_2O)为原料,通过简单的控制TAA的投量,利用水热法制备了不同S量掺杂的ZnS纳米晶粒.XRD分析表明所合成样品均为六方相的ZnS,通过Scherrer公式计算出其晶粒大小约为21nm,紫外-可见漫反射吸收光谱显示所合成样品在400～600nm范围内有部分吸收,可见光降解罗丹明B的光催化反应表明S掺杂ZnS样品对罗丹明B有一定的可见光光催化活性.笔者认为,S以填隙掺杂方式进入ZnS,在其中产生杂质能级,改善了样品可见光吸收特性,并最终产生可见光光催化活性.     

紫外光下Ag掺杂TiO2薄膜基底对VO2相转变温度的影响

利用溶胶−凝胶法和浸渍提拉技术制备了不同结构银掺杂二氧化钛薄膜为基底材料的VO₂薄膜,考察了Ag分级配置的二氧化钛薄膜基底材料对VO₂薄膜相变温度的影响。在紫外灯照射下测试面内电阻随温度,电压随时间的变化,结果表明基底材料为Ag分级配置的VO₂/TiO₂薄膜相变温度点明显降低。这可能是由于光照条件下空穴载流子从基底材料注入到VO₂薄膜导致相变温度点偏移。因此,不同结构银掺杂二氧化钛薄膜为基底材料的VO2薄膜能够根据环境温度和太阳光线变化而应用于光热致变色智能窗。     

High UV/visible light activity of mixed phase titania: A generic mechanism

Synergistic effect of the mixed phase in titania photocatalyst on its performance compared to the pristine phases has been investigated in terms of the bulk and interfacial behavior of the phases in contact. The experiments were conducted under both UV and visible light irradiations. The photoactivity variation has been correlated with the changes in the ratio of anatase to rutile phases (A/R ratio), and their unique response to UV and visible radiations. For this, a set of pure (rutile or anatase) and mixed phases (with varying A/R ratio) titania nanoparticles were synthesized. The physico-chemical characterization was done using SEM, XRD, EDAX, UV-DRS, PL and FTIR analyses. The activity of catalysts in UV and visible light was investigated by monitoring the degradation of phenol. The results show that the mixed phase catalysts show enhanced photoactivity compared to pristine phases across the irradiation wavelength range. Further, the catalysts having a narrow range of high A/R ratio (>1) around 5.0 show high UV activity while those having low A/R ratio (<1) around 0.5 show high visible light activity. A mechanism is proposed based on the influence of interfacial phenomena under both UV and visible light irradiations. It explains the differences observed in the behavior of the catalyst irradiated with UV and visible light and also the high activity of mixed phase catalysts compared to the pristine phases across the wavelength ranges.     

Visible-light-driven TiO2 catalysts doped with low-concentration nitrogen species

Visible-light-driven nitrogen-doped TiO₂ was synthesized using a novel nitrogen-ion donor of hydrazine hydrate. Low-concentration (0.2 at%) nitrogen species and Ti³⁺ were detected in the TiO₂-based photocatalyst by X-ray photoelectron spectroscopy (XPS) and electron paramagnetic resonance (EPR) spectroscopy. The trace amount of Ti–N would contribute to the minor band-gap narrowing of about 0.02 eV. Those nitrogen-containing species, especially the NO₂²⁻ species, form surface states, which make the catalysts possible to degrade 4-chlorophenol (4-CP) under visible irradiation (λ>400 nm). Moreover, Ti³⁺ species induce oxygen vacancy states between the valence and the conduction bands, which would also contribute to the visible response. The photocatalytic activity of the nitrogen-doped TiO₂ catalyst was thought to be the synergistic effect of nitrogen and Ti³⁺ species. The catalysts showed higher photocatalytic activity for degradation of 4-CP than pure TiO₂ under not only visible but also UV irradiation. The visible response and the higher UV activity of the nitrogen-doped TiO₂ make it possible to utilize solar energy efficiently to execute photocatalysis processes.     

TiO_2/C复合毫米球的制备及可见光催化活性研究

应用溶剂热条件下离子交换方法制备了C掺杂TiO2毫米球光催化剂。并通过元素分析、X射线衍射(XRD)、紫外-可见(UV-Vis)漫反射对其进行了表征。结果表明,TiO2为锐钛矿相,UV-Vis漫反射分析显示,与商业用P25相比,TiO2吸收边带红移,可见光吸收增强,同时证明C以掺杂的方式对TiO2进行了改性。以可见光催化降解甲基橙(MO)考察了材料的光催化活性,与P25相对比,C掺杂TiO2的光催化活性明显提高,并且催化剂可以通过自身重力沉降到反应容器底部,实现自分离。     

TiO2-B-S光催化剂的制备及性能研究

利用水热法直接制备了B、S共掺杂改性的光催化剂TiO_2-B-S。XRD表明该光催化剂为锐钛矿晶型,硫硼掺杂能抑制TiO_2粒径的生长;UV-vis表明该催化剂对可见光吸收增强,吸收带边明显红移。XPS显示B、S共掺杂改性使得TiO_2-B-S表面羟基氧含量提高,从而提高了催化剂活性。太阳光降解甲基橙溶液结果表明,TiO_2-B-S活性明显高于单一B、S掺杂改性催化剂,共掺杂改性对提高TiO_2可见光活性具有协同效应。     

The structure and photocatalytic studies of N-doped TiO2 films prepared by radio frequency reactive magnetron sputtering

N-doped TiO₂ films were prepared by a radio frequency reactive magnetron sputtering (RF-MS) deposition method from an undoped TiO₂ target in a mixture of Ar/N₂ atmosphere on heated quartz glass substrates. The structures and properties of the N-doped were studied by XRD, Raman, XPS, TEM, ultraviolet (UV)-vis and PL spectroscopy. By analyzing the structures and photocatalytic activities of undoped and N-doped TiO₂ films under ultraviolet and visible light irradiation, the probable photocatalytic mechanism of N-doped TiO₂ films was investigated. Because many oxygen defects are caused in films by nitrogen doping, it is presumed that nitrogen doping and oxygen defect induced the formation of new states closed to the valence band and conduction band, respectively. The cooperation of nitrogen and oxygen defects leads to a significant narrowing of the band gap and greatly improves the absorption in the visible light region. It is found that the degradation efficiencies of N-doped TiO₂ films greatly decreased under ultraviolet irradiation, but slowly improved under visible light irradiation, compared with the undoped TiO₂ film. It is suggested that the N-doped TiO₂ films are formed for the nitrogen to occupy oxygen defect sites directly. The doped nitrogen ions and oxygen defects act as recombination centers that reduce the lifetime of photo-induced electrons and holes, thereby resulting in the decrease of photocatalytic activity under ultraviolet light illumination.     

Recent progress in metal-doped TiO2, non-metal doped/codoped TiO2 and TiO2 nanostructured hybrids for enhanced photocatalysis

Titanium dioxide remains a benchmark photocatalyst with high stability, low cost, and less toxicity, but it is active only under UV light; thus, in practical applications using visible light, its catalytic reactions are stalled. To enhance its catalytic activity under visible light, non-metal/codoped TiO₂ structures are being studied. These structures improve the photocatalytic activity of TiO₂ in visible light by reducing its energy bandgap. This might be useful in wastewater treatment for the photocatalytic degradation of organic contaminants under visible and UV light irradiation. In this intensive review, we describe recent developments in TiO₂ nanostructured materials for visible-light driven photocatalysis, such as (i) mechanistic studies on photo-induced charge separation to understand the photocatalytic activity and (ii) synthesis of non-metal doped/codoped TiO₂ and TiO₂ nanostructured hybrid photocatalysts. Furthermore, the effects of various parameters on their photocatalytic efficiency, photodegradation of various organic contaminants present in wastewater, and photocatalytic disinfection are delineated.     

One-pot solvothermal synthesis of 1D plasmonic TiO2@Ag nanorods with enhanced visible-light photocatalytic performance

A plasmonic photocatalyst is designed and synthesized by coating TiO₂ nanoparticles onto the surface of Ag nanorods (Ag NRs), namely one-dimensional TiO₂@Ag NRs photocatalyst. Materials characterizations suggest that the as-prepared catalysts consist of a uniform and high crystalline anatase nanocrystals and highly conductive Ag nanorod. It delivers remarkable visible-light photocatalytic performance in simultaneous H₂ evolution and decomposition of methyl orange (MO) due to the synergetic effects of plasmonic resonance under visible light irradiation, a matched heterojunction, high surface area and large conductivity.     

TiO2–SiO2 mixed oxides: Organic ligand templated controlled deposition of titania and their photocatalytic activities for hydrogen production

A simple approach to the controlled deposition of titania with different particle sizes on silica surface has been developed by impregnation of an organic titania precursor followed by calcination. Among the several Ti-complexes tested, the templating effect of titanium phthalocyanine dichloride resulted in silica-supported titania with enhanced photocatalytic activity for photosplitting of water under UV light irradiation. The titania–silica materials were characterized by Powder X-ray diffraction (XRD), UV–Vis diffuse reflectance spectra (DRS), nitrogen adsorption studies, and Raman spectroscopic studies. The photocatalytic activity for hydrogen production is maximum at an optimal particle size wherein surface and volume recombination is minimized.     

Nitrogen-doped porous carbons derived from sustainable biomass via a facile post-treatment nitrogen doping strategy: Efficient CO2 capture and DRM

Nitrogen (N)-doped carbon materials have become promising candidates for many applications. In this paper, the biomass activated carbon (BC) was obtained by carbonization and activation of soybean meal. Using soybean meal as the precursor, potassium hydroxide (KOH) as the activator and melamine as the nitrogen source, a series of N-doped porous biomass carbons (H-NC-X) with different N contents were achieved via a facile post-treatment nitrogen doping strategy. Then these samples were used as a catalyst for dry reforming of methane (DRM) reaction and an adsorbent for CO₂ capture. Among all the investigated samples, BC has the largest specific surface area and the best pore structure characteristics, showing the best CO₂ adsorption capacity. However, when BC was used as a catalyst for DRM reaction, it showed the worst catalytic performance. After nitrogen doping treatment, the CO₂ adsorption capacity of the prepared N-doped biomass porous carbon decreased gradually with the increase of the introduced N content. This is mainly due to the destruction of the microporous structure of porous carbon by post-processing nitrogen doping. In contrast, when nitrogen-doped porous carbon was used as the reforming catalyst, the catalytic activity increased with the increase of the introduced N content. The order was: H-NC-30>H-NC-20>H-NC-10. This indicates that when nitrogen-doped porous carbon was used as an adsorbent, the pore structure plays a major role; while when it was used as a reforming catalyst, nitrogen functional groups are the major active sites. This study provides a promising N-doped carbon material for effect CO₂ adsorption and DRM reactions.     

Fabrication of direct Z-scheme MoO3/N–MoS2 photocatalyst for synergistically enhanced H2 production

A novel visible-light active MoO₃/N–MoS₂ heterostructure photocatalyst was fabricated via hydrothermal process. The structure, morphology and optical characteristics were studied using X-ray diffraction (XRD) technique, scanning electron microscopy (SEM), UV–visible and photoluminescence (PL) spectroscopies. The results indicated that loading pf MoO₃ and nitrogen doping played main influence role in advancing the morphology and optical characteristics. Upon visible photo-illumination, the MoO₃/N–MoS₂ sample displayed superior photocatalytic H₂-production activity (118 μ mol h⁻¹g⁻¹), which was about four-time higher than that of pure MoS₂ (30 μ mol h⁻¹g⁻¹). The enhancement in photocatalytic performance of MoO₃/N–MoS₂ photocatalyst can be ascribed to the development of direct Z-scheme heterostructure, which promoted the photo-excited electrons/holes transfer and separation. The recycling experiment verified that the MoO₃/N–MoS₂ photocatalyst had superior cyclic activity and stability, implying promising applications in energy field.