石墨烯助剂与Ni(Ⅱ)活性位点协同增强TiO2制氢性能

采用水热法和低温浸渍法制备了电子助剂还原石墨烯(rGO)和界面活性位点Ni(Ⅱ)共修饰的高效TiO₂光催化剂(简称Ni(Ⅱ)/TiO₂-rGO)。制氢性能测试结果表明：相比于TiO₂和单独还原石墨烯复合的TiO₂,经还原石墨烯与Ni(Ⅱ)协同修饰后的TiO₂表现出更高的光催化制氢性能。其中,Ni(Ⅱ)/TiO₂-rGO(0.1 mol·L^-1)具有最高制氢性能,制氢速率达到77.0 μmol·h^-1,分别是TiO₂(16.4 μmol·h^-1)和TiO₂-rGO(28.0 μmol·h^-1)的4.70倍和2.75倍。还原石墨烯助剂与Ni(Ⅱ)活性位点协同增强制氢性能的原理是：还原石墨烯作为电子助剂可以快速捕获和传输电子,Ni(Ⅱ)作为界面活性位点可以从溶液中捕获H⁺,提高界面反应速率,2种助剂协同作用加快了TiO₂上的光生电子-空穴对的有效分离。     

TiO2/石墨烯复合材料的合成及光催化分解水产氢活性

利用石墨粉根据Hummers氧化法制得氧化石墨,并进一步还原得到石墨烯。采用溶胶-凝胶法以钛酸四丁酯和石墨烯为起始材料制备了二氧化钛(TiO₂)和石墨烯的复合光催化材料。研究了该复合材料在紫外-可见光以及可见光条件下的光催化分解水制氢活性。结果表明,紫外-可见光照射下,TiO₂/石墨烯复合光催化材料的光催化分解水产氢速率为8.6 μmol·h^-1,远大于同条件下商业P25的产氢速率 (4.5 μmol·h^-1),光解水产氢活性提高了近2倍;可见光下光照3 h,TiO₂/石墨烯复合材料的光催化分解水产氢量约为0.2 μmol。     

Gd3+掺杂TiO2纳米复合材料的可见光响应性能

采用溶胶-凝胶技术,在钛酸四丁酯(TBOT)的水解过程中,加入硝酸钆(Gd(NO₃)₃),得到具有可见光响应活性的Gd³⁺/TiO₂复合材料。应用TEM、XRD、TG-DTA和UV-Vis等手段对纳米TiO₂复合材料进行了表征。当Gd³⁺的掺杂量为0.5%时,Gd³⁺/TiO₂复合材料在550 nm附近产生宽强吸收带。Gd³⁺进入TiO₂晶格中,形成了新的掺杂能级(E_g=1.27 eV)。适量Gd³⁺掺杂的纳米TiO₂复合材料的光催化性能优于纯TiO₂粉体材料。     

“开放型蝶形”[2Fe2S]化合物光催化产氢性能与机理探究

合成并表征了两个新的具有 “开放型蝶形” 结构的[2Fe2S]化合物A和B; 并以A和B为催化剂、 藻红B钠盐 (EBS^2-) 为光敏剂、 三乙胺 (TEA) 为电子给体和质子源, 构建了一个均相光催化产氢体系. 结果表明: 体系在pH为12, 体积比为1∶1的CH₃CN/H₂O溶液中,产氢活性最高,经4 h可见光照射,最大产氢量分别为156.1 μmol (37.9 TON vs. A) 和18.4 μmol (TON 4.6 vs. B); 催化剂中含有质子捕获位点, 有利于形成产氢活性中间体H₂-Fe₂S₂(η²-H²-Fe^IIFe^I) 物种, 从而提高催化剂的产氢活性. 在当前的体系中, 还原态的 Fe^IFe⁰ 物种通过^1* EBS^2-转移到Fe^IFe^I中心上, 然后再经历一个EECC (化合物A) 或ECEC (化合物B), 形成产氢活性中间体H₂-Fe₂S₂(η²-H₂-Fe^IIFe^I)物种, 最终产生H₂分子, 并使Fe^IFe^I 物种再生.     

TiO2/Gd2O3纳米粉体的制备、表征及光催化活性

利用酸催化的溶胶-凝胶法制备了纯TiO₂和Gd³⁺(0.5wt%)掺杂的TiO₂纳米粉体，采用XRD、BET、XPS、紫外-可见漫反射谱(DRS)和表面光电压谱(SPS)等技术进行了表征；以亚甲基蓝(MB)的光催化降解为探针反应，评价了其光催化活性；探讨了Gd³⁺掺杂对TiO₂纳米粉体的光催化活性的影响机制。结果表明，TiO₂/Gd₂O₃纳米粒子对MB溶液的光催化活性提高到纯TiO₂的1.5倍。掺杂Gd³⁺可以强烈抑制TiO₂由锐钛矿相向金红石相的转变；阻碍TiO₂晶粒的生长；提高高温组织稳定性，改善粉体的表面织构特性；形成光生电子的浅势捕获陷阱，抑制e^-/h⁺复合，这些因素共同作用最终导致TiO₂/Gd₂O₃纳米粉体的光催化活性明显提高。XPS分析结果证实，掺杂Gd³⁺导致粉体的表面羟基含量降低。由于产生了量子尺寸效应，复合粉体的紫外吸收带边蓝移，光的吸收能力略有降低。     

高比表面TiO2光催化剂的制备及产氢性能研究

以钛酸四丁酯为前驱体，十六烷基三甲基溴化铵(CTAB)为模板剂合成了高比表面的TiO₂超细纳米粉体。采用XRD、TEM、BET分析方法对催化剂的物相、颗粒粒径及比表面积进行了表征，结果显示TiO₂的晶粒尺寸和比表面积与CTAB添加量和焙烧温度有关。重点考察了不同条件下制备的TiO₂系列光催化剂无氧条件下的光催化分解水产氢性能。实验结果表明，当CTAB与Ti的投料的物质的量之比为0.15，焙烧温度为450 ℃时，获得的晶粒尺寸为5.73 nm、比表面为150 m²·g^-1的TiO₂粉体具有最好的光催化产氢活性，测得的3 h内平均产氢速率为12.5 mL·h^-1。     

锰掺杂硒硫化镉光阳极的制备与光电性能

将适量Se加入到Na2S甲醇水溶液中反应生成Na₂SSe₂阴离子前驱体, 以Cd(NO₃)2、Mn(CH3COO)2为阳离子前驱体, 通过连续离子层吸附反应(SILAR)分别制备出CdSSe₂/TiO₂或 MN²⁺掺杂的Mn-CdSSe₂/TiO₂量子点敏化光阳极。采用拉曼光谱、X射线光电子能谱和能量色散X射线能谱分析确定阴离子前驱体和量子点的价键结构和组成;通过紫外可见吸光光谱表征量子点的光吸收性能;利用J-V曲线和IPCE分别对CdS、CdSSe₂和Mn-CdSSe₂量子点敏化的TiO₂光阳极的光电性能进行了表征。实验结果表明, 采用 0.12 mol·L^-1 Se和0.5 mol·L^-1 Na2S制备的阴离子前驱体、0. 5 mol·L^-1 Cd²⁺和 0.3 mol·L^-1 MN²⁺阳离子前驱体, 通过SILAR法制备的Mn-CdSSe₂/TiO₂光阳极, 能量转换效率比CdSSe₂/TiO₂和CdS/TiO₂光阳极分别提高了90%和247%。     

过硫酸盐激活协同可见光催化降解四环素的机理和降解路径

为了提升微污染水体中抗生素的降解效率,利用过硫酸钠(PDS)激活协同手性介孔TiO₂可见光催化(PDS/vis-TiO₂)对四环素(TC)进行降解。详细对比研究了以手性TiO₂作为催化剂的PDS激活(PDS/TiO₂)、可见光催化(vis-TiO₂)和PDS/vis-TiO₂三种体系中,降解污染物的活性物种和污染物降解路径等的差异。结果表明,不对称的螺旋堆积结构在手性介孔TiO₂中引入了丰富的Ti³⁺,不仅提升了其可见光响应,同时能够激活PDS生成自由基。PDS/vis-TiO₂体系中光生空穴h⁺和·OH等多种自由基可以同时参与TC的降解,5 h内其对TC去除率可达到95%以上,远超PDS/TiO₂体系(TC去除率为48.9%)和vis-TiO₂体系(TC去除率为71.1%)。PDS加入到光催化体系中,会受到光生电子的激活而产生自由基,从而消耗光生电子,提升光生空穴和电子的分离率,达到协同增强污染物的降解能力。另外PDS激活后产生自由基也会大大增加体系对TC的降解性能。密度泛函理论计算和中间产物分析结果表明,TC在PDS/vis-TiO₂体系中的降解路径包含了光生空穴h⁺攻击TC的降解路径,同时也包括自由基攻击TC的降解路径。     

Pt 改性的高结晶度 TiO2 晶须的光催化性能

 以二钛酸钾 (K₂Ti₂O₅) 为前驱体, 通过离子交换和 800^oC 焙烧制备了 TiO₂晶须 (TiO₂(800^oC)), 并采用乙二醇胶体法, 在 TiO₂(800^oC) 样品上负载 1% Pt 纳米颗粒制成了 Pt/TiO₂(800^oC 催化剂. 采用 X 射线衍射、扫描电镜、透射电镜、X 荧光光谱和低温 N2 吸附-脱附等技术对催化剂进行了表征, 并考察了该催化剂光催化降解苯酚活性及稳定性. 结果表明, TiO₂(800^oC)样品为结晶度较高的纯锐钛矿 TiO₂, 载 Pt 后催化活性提高到原来的 2.3 倍, 具有很高的单位比表面积活性. 催化剂经 10 次重复使用后, Pt 流失量仅为 6%, 活性为新鲜催化剂的 91%. 而低结晶度的纯锐钛矿或混晶的 TiO₂ 负载 Pt 催化剂的活性和稳定性均不及 Pt/TiO₂(800^oC).     

水热法制备具有高光催化活性的镧掺杂二氧化钛纳米晶

采用水热法合成钛酸钾(K₂Ti₈O₁₇)纳米棒,并将它作为前驱体水热转晶合成TiO₂纳米晶,同时通过在水热体系中引入稀土元素La³⁺实现对TiO₂的La掺杂.考察了不同条件下钛酸盐向TiO₂的转晶过程,发现水热溶液的pH值、温度以及预处理步骤对转晶过程有很大的影响.利用X射线衍射以及透射电子显微镜对样品的晶相和形貌进行了表征.利用电感耦合等离子体原子发射光谱测量了所合成的La掺杂TiO₂样品中的La含量.通过在紫外光下降解甲基橙(MO,10mg/L)测试了La掺杂TiO₂样品的光催化性能.结果表明La掺杂后TiO₂的光催化活性大大提高.在0.15mol/LLa³⁺浓度下180oC水热合成的La掺杂TiO₂样品显示了最佳的光催化活性.其对MO的光催化降解反应常数高达0.11min^-1,大约是空白TiO₂样品的9.20倍,P25TiO₂的3.69倍.     

Engineering the Atomic Interface with Single Platinum Atoms for Enhanced Photocatalytic Hydrogen Production

It is highly desirable but challenging to optimize the structure of photocatalysts at the atomic scale to facilitate the separation of electron–hole pairs for enhanced performance. Now, a highly efficient photocatalyst is formed by assembling single Pt atoms on a defective TiO₂ support (Pt₁/def‐TiO₂). Apart from being proton reduction sites, single Pt atoms promote the neighboring TiO₂ units to generate surface oxygen vacancies and form a Pt‐O‐Ti³⁺ atomic interface. Experimental results and density functional theory calculations demonstrate that the Pt‐O‐Ti³⁺ atomic interface effectively facilitates photogenerated electrons to transfer from Ti³⁺ defective sites to single Pt atoms, thereby enhancing the separation of electron–hole pairs. This unique structure makes Pt₁/def‐TiO₂ exhibit a record‐level photocatalytic hydrogen production performance with an unexpectedly high turnover frequency of 51423 h^?1, exceeding the Pt nanoparticle supported TiO₂ catalyst by a factor of 591.     

Porous TiO2 Nanotubes with Spatially Separated Platinum and CoOx Cocatalysts Produced by Atomic Layer Deposition for Photocatalytic Hydrogen Production

Efficient separation of photogenerated electrons and holes, and associated surface reactions, is a crucial aspect of efficient semiconductor photocatalytic systems employed for photocatalytic hydrogen production. A new CoO_x/TiO₂/Pt photocatalyst produced by template‐assisted atomic layer deposition is reported for photocatalytic hydrogen production on Pt and CoO_x dual cocatalysts. Pt nanoclusters acting as electron collectors and active sites for the reduction reaction are deposited on the inner surface of porous TiO₂ nanotubes, while CoO_x nanoclusters acting as hole collectors and active sites for oxidation reaction are deposited on the outer surface of porous TiO₂ nanotubes. A CoO_x/TiO₂/Pt photocatalyst, comprising ultra‐low concentrations of noble Pt (0.046 wt %) and CoO_x (0.019 wt %) deposited simultaneously with one atomic layer deposition cycle, achieves remarkably high photocatalytic efficiency (275.9 μmol h⁻¹), which is nearly five times as high as that of pristine TiO₂ nanotubes (56.5 μmol h⁻¹). The highly dispersed Pt and CoO_x nanoclusters, porous structure of TiO₂ nanotubes with large specific surface area, and the synergetic effect of the spatially separated Pt and CoO_x dual cocatalysts contribute to the excellent photocatalytic activity.     

Synthesis of Bi-doped TiO2 Nanotubes and Enhanced Photocatalytic Activity for Hydrogen Evolution from Glycerol Solution

Bi‐doped TiO₂ nanotubes with variable Bi/Ti ratios were synthesized by hydrothermal treatment in 10 mol·L^?1 NaOH (aq.) through using Bi‐doped TiO₂ particles derived from conventional sol‐gel method as starting materials. The effects of Bi content on the morphology, textural properties, photo absorption and photocatalytic activity of TiO₂ nanotubes were investigated. The scanning electron microscopy (SEM), transmission electron microscopy (TEM), X‐ray diffraction (XRD) and X‐ray photoelectron spectroscopy (XPS) observations of the obtained samples revealed the formation of titanate nanotube structure doped with Bi, which exists as a higher oxidation state than Bi³⁺. Bi‐doping TiO₂ nanotubes exhibited an extension of light absorption into the visible region and improved photocatalytic activities for hydrogen production from a glycerol/water mixed solution as compared with pure TiO₂ nanotubes. There was an optimal Bi‐doped content for the photocatalytic hydrogen production, and high content of Bi would retard the phase transition of titanate to anatase and result in morphology change from nanotube to nanobelt, which in turn decreases the photocatlytic activity for hydrogen evolution.     

Sulfur and Ti3+ co‐Doping of TiO2 Nanotubes Enhance Photocatalytic H2 Evolution Without the Use of Any co‐catalyst

TiO₂ nanotubes were successfully co‐doped with sulfur and Ti³⁺ states using a facile annealing treatment in H₂/H₂S gas mixture. The obtained nanotubes were investigated for their photocatalytic performance and characterized by SEM, XRD, XPS, EPR, IPCE, IMPS and Mott‐Schottky measurements. The synthesized co‐doped TiO₂ nanotubes show an enhanced photocatalytic hydrogen production rate compared to tubes that were treated only in pure H₂ or H₂S atmosphere—this without the presence of any co‐catalyst. It was found that sulfur in co‐doped TiO₂ exists in the form of S^2? and a small quantity of S⁴⁺/S⁶⁺, which leads to a narrowing of the band gap. However, the enhanced absorption of light in the visible range is not the key reason for the improved photocatalytic performance. We ascribe the enhanced photocatalytic activity to a synergetic effect of S mid‐gap states and disordered Ti³⁺ defects that facilitate photo generated electron transfer.     

Hierarchical TiO2 nanosheet‐assembled nanotubes with dual electron sink functional sites for efficient photocatalytic degradation of rhodamine B

A novel Pt–TiO₂/Ag nanotube photocatalyst has been synthesized successfully via a facile method. TiO₂ nanotubes are assembled with numerous ultrathin TiO₂ nanosheets and show a highly open structure. The gaps between adjacent TiO₂ nanosheets can serve as channels for the access of reactants, accelerating the mass transfer process. During the fabrication process of the Pt–TiO₂/Ag nanotube photocatalyst, high‐quality Pt–SiO₂ nanotubes are synthesized first with the structure‐directing effect of polyvinylpyrrolidone. Then a TiO₂ layer is coated on the outside surface of the silica nanotubes. The introduced titanium species can be converted into TiO₂ nanosheet structure during the subsequent hydrothermal treatment, gradually constructing nanosheet‐assembled nanotubes. Lastly, after the introduction of another electron sink function site of Ag through UV irradiation, the Pt–TiO₂/Ag nanotube photocatalyst with dual electron sink functional sites is obtained. The specially doped Pt and Ag NPs can simultaneously inhibit the recombination process of photogenerated charge carriers and increase light utilization efficiency. Therefore, the as‐synthesized Pt–TiO₂/Ag nanotube catalyst exhibits a high photocatalytic degradation performance for rhodamine B of 0.2 min^?1, which is about 3.2 and 5.3 times as high as that of Pt–TiO₂ and TiO₂ nanotubes because of the enhanced charge carrier separation efficiency. Furthermore, in the unique nanoarchitecture, the nanotubes are assembled with numerous ultrathin TiO₂ nanosheets, which can absorb abundant active species and dye molecules for photocatalytic reaction. On the basis of experimental results, a possible rhodamine B degradation mechanism is proposed to explain the excellent photocatalytic efficiency of the Pt–TiO₂/Ag nanotube photocatalyst.     

Band Structure Engineering of Single Pt Atoms on Fe−TiO2 for Enhanced Photocatalytic Performance

Single atomic site catalysts display the maximal atom-utilization efficiency, unique structural properties, and remarkable enhancements on catalytic activity. Herein, single Pt atoms loaded Fe−TiO₂ catalysts were prepared. Fe³⁺ doping leads to the formation of oxygen vacancies and improve the interaction between TiO₂ and Pt. Single Pt atoms are thus anchored and effectively modify the local energy band structure of TiO₂. The optimized local band structures improve the intrinsic photoexcitation of Pt/Fe−TiO₂, promote the separation of photogenerated carriers, and extend the lifetime of photogenerated carriers. Meanwhile, the electrons transfer from the excited dyes to the conduction band edge of Pt/Fe−TiO₂ is also facilitated due to the shift-down of the conduction band edge. Therefore, with the increase of the Pt content (till up to 0.6 wt%), the photocatalytic performance of Pt/ Fe−TiO₂ with the confined single Pt atoms is significantly boosted in either the intrinsic or the sensitized photocatalytic process.     

载钛羟基磷灰石光催化降解内分泌干扰物双酚A

对载钛羟基磷灰石（TiHAP）进行了透射电镜、X射线衍射、紫外-可见光谱和Zeta电位表征,并应用液相色谱-质谱技术对比了TiHAP和P25 TiO₂对环境内分泌干扰物双酚A（BPA）的吸附和光催化降解性能,探讨了富里酸和Fe³⁺对TiHAP薄膜光催化性能的影响。结果表明,TiHAP和TiO₂粉体对BPA的吸附符合Langmuir吸附等温方程,且前者吸附性能更大。TiHAP薄膜光催化降解BPA的性能优于TiO₂薄膜;富里酸和Fe³⁺对TiHAP和TiO₂薄膜光催化性能的影响趋势不同,从能带结构、电子转移和吸光性等角度分析了性能不同的原因。本结果可以为应用TiHAP降解环境内分泌干扰物提供依据。     

Pt deposited TiO2 catalyst fabricated by thermal decomposition of titanium complex for solar hydrogen production

C, N codoped TiO₂ catalyst has been synthesized by thermal decomposition of a novel water-soluble titanium complex. The structure, morphology, and optical properties of the synthesized TiO₂ catalyst were characterized by X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, and UV–vis diffuse reflectance spectroscopy. The photocatalytic activity of the Pt deposited TiO₂ catalysts synthesized at different temperatures was evaluated by means of hydrogen evolution reaction under both UV–vis and visible light irradiation. The investigation results reveal that the photocatalytic H₂ evolution rate strongly depended on the crystalline grain size as well as specific surface area of the synthesized catalyst. Our studies successfully demonstrate a simple method for the synthesis of visible-light responsive Pt deposited TiO₂ catalyst for solar hydrogen production.     

Inclusion of methylviologen dication in a cadmium tetracyanoplatinate host clathrate showing photochromism and photoluminescence modulation

A cadmium tetracyanoplatinate host clathrate, (MV)[Cd₂{Pt(CN)₄}₃]?2(H₂O) (1), including a methylviologen dication (MV²⁺) was synthesized, and the crystal structures, photochromic and photoluminescence properties were investigated. In 1, the alternatively parallel stacking between the MV²⁺ dications as electron acceptors in the channels and the electron donors [Pt1(CN)₄]^2– units in the host frameworks give a unique donor-acceptor (DA) system. Under UV irradiation, the electron transfer between MV²⁺ and [Pt(CN)₄]^2– ions generates MV^·+ radicals with a photochromic behavior from pale-yellow to blue. This process occurs through single-crystal-to-single-crystal (SCSC) transformation and obvious structure variation of viologen cations is successfully observed. Moreover, the spectral overlap between the emission bands of 1 and the absorption around 623 nm for the MV^·+ radicals leads to a modulation of the photoluminescence.     

Photocatalytic hydrogen evolution over mesoporous TiO2/metal nanocomposites

Na⁺ complex with the dibenzo-18-crown-6 ester was used as a template to synthesize mesoporous titanium dioxide with the specific surface area 130–140 m²/g, pore diameter 5–9 nm and anatase content 70–90%. The mesoporous TiO₂ samples prepared were found to have photocatalytic activity in Cu^II, Ni^II and Ag^I reduction by aliphatic alcohols. The resulting metal–semiconductor nanostructures have remarkable photocatalytic activity in hydrogen evolution from water–alcohol mixtures, their efficiency being 50–60% greater than that of the metal-containing nano-composites based on TiO₂ Degussa P25.The effects of the thermal treatment of mesoporous TiO₂ upon its photocatalytic activity in hydrogen production were studied. The anatase content and pore size were found to be the basic parameters determining the photoreaction rate. The growth of the quantum yield of hydrogen evolution from TiO₂/Ag⁰ to TiO₂/Ni⁰ to TiO₂/Cu⁰ was interpreted in terms of differences in the electronic interaction between metal nanoparticles and the semiconductor surface. It was found that there is an optimal metal concentration range where the quantum yield of hydrogen production is maximal. A decrease in the photoreaction rate at further increment in the metal content was supposed to be connected with the enlargement of metal nanoparticles and deterioration of the intimate electron interaction between the components of the metal–semiconductor nanocomposites.