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1.
为了应对日益加剧的环境和能源危机,利用太阳能生产化学燃料迫在眉睫.太阳能光催化水分解产氢因其可利用阳光生产绿色H2燃料被认为是一种廉价且环境友好的技术.但是,要实现理想的产H2通常依赖于牺牲试剂的消耗,这会增加成本并会产生无利用价值的氧化产物.实际上,生物质(醇、胺和糖)可以替代牺牲试剂,在产生H2的同时获得有经济价值的化学品.其中,苯甲醇的C–C偶联氧化产物包括安息香、脱氧安息香、氢化安息香等,这些氧化产物是合成具有生物活性聚合物引发剂的重要结构基序.然而,目前光催化氧化苯甲醇的主要产物是苯甲醛,很少得到高选择性的C–C偶联产物.因此,设计一种能够同时实现光催化产氢和C–C偶联产物的合成的新型光催化剂是光催化领域面临的重要挑战.本文制备了Co纳米颗粒负载的共暴露(001)/(101)晶面的相结Cd S,并应用于光催化氧化苯甲醇合成氢化安息香和产氢.可见光下照射9 h后, HC-Cd S2/Co的光催化产氢速率达到11 mmol·g–1,分别是C-Cd S/Co和HC-Cd S2产氢速率的4.7倍和34倍.在HC-Cd S2上负载Co后,氢化安息香的选择性由12%...  相似文献   

2.
油滴堵塞导致的膜污染问题限制了膜技术在油水分离中的应用,构建选择性分离油水混合液的功能界面是实现高效油水分离的重要途径.本文制备了Ti O2(001)和(101)晶面暴露的g-C3N4/Ti O2-PVDF(聚偏氟乙烯膜)光催化膜,研究了不同暴露晶面对油水分离效果的影响及作用过程.结果显示,光照射下,Ti O2(001)晶面赋予了g-C3N4/Ti O2(001)-PVDF膜优异的超亲水和水下超疏油特性,与Ti O2(101)晶面暴露的膜相比,g-C3N4/Ti O2(001)-PVDF膜具有更优异的油水分离性能.g-C3N4/Ti O2(001)PVDF膜在可见光照射下,纯水通量达到2002.9 L·m?2·h?1,...  相似文献   

3.
用等体积浸渍法制备了不同Pd负载量的Pd/Cd0.8Zn0.2S/SiO2光催化材料,采用XRD、H2-TPR、XPS、UV-vis DRS和光催化反应评价等方法对光催化材料的表面结构、光吸收性能以及光催化甘油水溶液制氢反应性能进行了考察。研究结果表明,ZnS与CdS在SiO2表面形成了Cd0.8Zn0.2S固溶体,金属Pd负载未对固溶体Cd0.8Zn0.2S/SiO2的结构造成影响;金属Pd修饰明显地提高了原固溶体的光响应性能,拓展了其吸光域,增强了吸光效率。金属Pd修饰后,Cd0.8Zn0.2S/SiO2的光解甘油水溶液产氢速率显著提高,Pd负载量为0.5%的Pd/Cd0.8Zn0.2S/SiO2具有最佳的光催化甘油水溶液制氢性能,其在紫外光照射下的氢气生成速率为831 μmol/h,较未负载时提高了近四倍;模拟太阳光下为153 μmol/h,较未负载时提高了近两倍。  相似文献   

4.
光催化CO2高效、环保地转化为高附加值化工产品(CH4, CO, CH3OH等),能够有效降低环境污染并且促进资源利用.商用P25(TiO2)因其具有无毒、化学稳定性和强氧化还原电位而被广泛研究.然而, TiO2的带隙高达3.0 e V,只有在紫外光激发下才能产生光生载流子,这极大地限制了其在光催化领域的应用.单原子催化剂(SACs)具有金属原子利用率高、选择性高和活性高等优点,可用于精细化工合成、氧还原和污染物降解等催化领域.由于单个原子具有极高的表面自由能,因此如何稳定地保持原子分散,避免原子团聚成为SACs制备和反应过程中的一大挑战.本文通过简单的负压封装后热解方法实现了Fe在TiO2表面的原子级分散负载,所制备的Fe SA/TiO2催化剂展现出高效的光催化CO2还原性能,并且利用多种表征手段及理论计算研究了TiO2表面Fe位点促进CO2高效转化的反应机制.扫描透...  相似文献   

5.
利用太阳能将CO2转换为高附加值的化学品是解决化石燃料消耗过快与CO2排放过度问题的可行性方案.光电催化CO2还原可以模拟自然光合作用将CO2还原为多碳产物(C2+).然而,光电催化剂的带隙与太阳辐射光谱不匹配以及载流子的快速复合是限制人工光合作用效率的关键因素.前期研究表明,缺陷工程可有效地增加催化剂活性位点,减小半导体的带隙并增强对光子的捕获能力;而异质结的构筑则可有效提升载流子的分离效率.因此,构建具有较好可见光响应的高效半导体异质结催化剂有望实现催化材料对CO2还原能力和产物选择性的提升.本文通过对金属钛板进行电化学阳极氧化,氨气气氛煅烧得到Ti N,然后原位进行部分氧化构筑出结构新颖的Ti O2/Ti N纳米管异质结材料,再进行配体和钯量子点修饰,得到更加高效的催化电极材料Pd/R-Ti O2/TiN,并在三电极系统中研究了其光电催化CO2还原的性能.通过扫描隧道电子显微镜、透射电...  相似文献   

6.
甲醇选择氧化制备甲酸甲酯(MF)是延伸甲醇产业链、开发高附加值下游产品的有效途径之一,负载型Au及Pd催化剂在这一反应中表现出优异的低温催化性能。为探索实用、高效和易再生的甲醇选择氧化催化剂,同时揭示双金属颗粒中Au和Pd的协同效应及甲醇氧化反应机理,本研究制备了一系列二氧化硅负载的Au-Pd催化剂(Au-Pd/SiO2),详细研究了其对甲醇选择氧化制甲酸甲酯的催化性能。结果表明,Au和Pd总负载量为0.6%、且Au/Pd质量比为2时,所制备的Au2-Pd1/SiO2催化剂表现出优异的甲醇氧化催化性能;在130℃下,甲醇转化率达到57.0%,MF选择性为72.7%。多种表征结果显示,Au-Pd双金属纳米颗粒粒径为2-4 nm,高度分散于SiO2载体表面,倾向于生成孪晶结构并暴露(111)晶面,这些因素是Au-Pd/SiO2具有优异催化性能的主要原因。通过DRIFTS表征研究,提出了一个可能的MF生成机理:即甲醇首先与处于Au-Pd纳米粒子界面的表面氧作用,生成化学吸附的甲氧基;随后,甲氧基经去质子作用生成吸附的甲醛物种,后者与相邻的甲氧基物种亲核反应,并经β-H消除后得到目标产物MF。  相似文献   

7.
绿色光催化技术在可持续水处理和环境修复领域具有广阔的应用前景.光催化效率在很大程度上取决于光催化剂,其中二氧化钛(Ti O2)因具有超强的光氧化能力、化学稳定性和低成本等优点而广泛应用于光催化降解水中各类有机污染物.然而,Ti O2的光催化效率仍然受限于其自身比表面积小、太阳光利用率低以及光生载流子复合速率快等缺点.为了克服以上缺点,进一步提高Ti O2的光催化效率,本研究采用简单易行的原位共缩合结合水热处理技术,以葡萄糖为碳源,四异丙氧基钛(TTIP)为钛源,成功制备了一系列由锐钛矿相Ti O2与石墨相碳组成的Ti O2/C复合光催化剂,它们在水中新兴酚类污染物的降解中表现出了优异的可见光光催化活性.通过X射线衍射、热重分析、X射线光电子能谱、孔隙率分析、扫描电镜、透射电镜、紫外-可见漫反射光谱等表征手段对催化剂的组成和结构、形貌、孔隙率性质及光吸收特性进行了表征.结果显示,Ti O2/C复合光催化剂具有独特的微孔/介孔结构,以及比Ti O2<...  相似文献   

8.
通过浸渍-沉淀法合成负载型双金属催化剂Ni-Co/TiO2,采用X射线衍射(XRD)、场发射扫描电子显微镜(FESEM)、X射线能谱(EDS)、透射电子显微镜(TEM)、X射线光电子能谱(XPS)和氮气吸附-脱附(BET)对其晶型、形貌、组成、表面元素价态和比表面积进行表征.在CO2加氢反应中,Ni-Co/Ti O2催化剂在3 h反应时间内生成84.4μmol CH4,相较于Ni/Ti O2催化剂,其CH4产量提高了46.3%.二氧化碳程序升温脱附(CO2-TPD)和氢气程序升温还原(H2-TPR)测试结果证实,Co的引入能增强Ni-Co/Ti O2对CO2的吸附和活化,从而促进其加氢反应效率的提高.经过5次循环活性测试,Ni/Ti O2的活性降低了20.5%,而Ni-Co/Ti O2的活性仅仅降低了10.9%,这表明Co的引...  相似文献   

9.
以O2为绿色氧化剂实现高效光催化有机物氧化转化过程如醇等有机物的选择性氧化及污染物降解是当前光催化发展的重要方向之一.成功实现高活性及高选择性的上述转化过程主要在于设计并制备有效的光催化材料.二氧化钛作为最广泛应用的光催化材料被报道用于光催化空气醇氧化选择性转化,但通常活性有限且因其表面催化活性位均为含有Ti-O6活性中心而具有较低的产物选择性.相比之下,同样作为Ti基材料的钛硅分子筛如TS-1分子筛具有高选择性的Ti-O4催化中心、丰富的孔结构及良好的稳定性,被广泛用于多种传统催化氧化反应.近年来, TS-1分子筛因具有光催化活性而成为一类具有工业应用潜力的光催化材料,特别是其独特的Ti-O4催化中心有望实现高选择性的光催化氧化转化.然而,其活性仍受限于较差的光生电荷分离,提升TS-1分子筛的电荷分离是促进其光催化活性的关键.本工作以特定结构的季铵盐表面活性剂为结构导向剂,通过低温水热法成功制备了TS-1分子筛纳米片,并通过离子交换法于TS-1分子筛纳米片的离子交换位引入二价镍离子,显著地提升了其...  相似文献   

10.
基于密度泛函理论的第一性原理从头计算方法,建立了Cl2和O2在TiC(100)表面的共吸附模型.通过分析吸附能、电荷密度和偏态密度(PDOS)等参数,研究了Cl2和O2在TiC(100)表面的反应机理,发现解离后的Cl原子和O原子与TiC(100)表面的原子均成键,从而破坏了Ti—C键.Cl2分子在吸附过程中充当电子的受体,得到与之成键的Ti原子贡献的电子,O2分子在吸附过程中也充当电子的受体,得到C原子贡献的电子.TiC(100)表面在吸附分子后,Ti—C成键轨道上电子占据数变少,反键轨道上电子占据数增多,Ti原子与C原子之间的成键作用减弱.同时,Ti3d与Cl3s,Cl3p发生轨道重叠杂化作用,O2p轨道和C2p轨道存在较强的共振峰,Cl原子和O原子与TiC表面相互作用强烈.  相似文献   

11.
The use of semiconductor photocatalysts (CdS, g-C3N4, TiO2, etc.) to generate hydrogen (H2) is a prospective strategy that can convert solar energy into hydrogen energy, thereby meeting future energy demands. Among the numerous photocatalysts, TiO2 has attracted significant attention because of its suitable reduction potential and excellent chemical stability. However, the photoexcited electrons and holes of TiO2 are easily quenched, leading to limited photocatalytic performance. Furthermore, graphene has been used as an effective electron cocatalyst in the accelerated transport of photoinduced electrons to enhance the H2-production performance of TiO2, owing to its excellent conductivity and high charge carrier mobility. For an efficient graphene-based photocatalyst, the rapid transfer of photogenerated electrons is extremely important along with an effectual interfacial H2-production reaction on the graphene surface. Therefore, it is necessary to further optimize the graphene microstructures (functionalized graphene) to improve the H2-production performance of graphene-based TiO2 photocatalysts. The introduction of H2-evolution active sites onto the graphene surface is an effective strategy for the functionalization of graphene. Compared with the noncovalent functionalization of graphene (such as loading Pt, MoSx, and CoSx on the graphene surface), its covalent functionalization can provide a strong interaction between graphene and organic molecules in the form of H2-evolution active sites that are produced by chemical reactions. In this study, carboxyl-functionalized graphene (rGO-COOH) was successfully modified via ring-opening and esterification reactions on the TiO2 surface by using an ultrasound-assisted self-assembly method to prepare a high-activity TiO2/rGO-COOH photocatalyst. The Fourier transform infrared (FTIR) spectra, X-ray photoelectron spectroscopy (XPS), and thermogravimetric (TG) curves revealed the successful covalent functionalization of GO to rGO-COOH by significantly enhanced ―COOH groups in FTIR and increased peak area of carboxyl groups in XPS. A series of characterizations, including X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), XPS, and UV-Vis adsorption spectra, were performed to demonstrate the successful synthesis of TiO2/rGO-COOH photocatalysts. The experimental data for the hydrogen-evolution rate showed that the TiO2/rGO-COOH displayed an extremely high hydrogen-generation activity (254.2 μmol∙h−1∙g−1), which was 2.06- and 4.48-fold higher than those of TiO2/GO and TiO2, respectively. The enhanced photocatalytic activity of TiO2/rGO-COOH is ascribed to the carboxyl groups of carboxyl-functionalized graphene, which act as effective hydrogen-generation active sites and enrich hydrogen ions owing to their excellent nucleophilicity that facilitates the interfacial hydrogen production reaction of TiO2. This study provides novel insights into the development of high-activity graphene-supported photocatalysts in the hydrogen-generation field.   相似文献   

12.
通过物理混合法可控合成了分级混晶TiO2微纳米材料, 采用扫描电子显微镜(SEM)、 透射电子显微镜(TEM)、 X射线衍射仪(XRD)、 X射线光电子能谱仪(XPS)和固体紫外-可见分光光度计(UV-Vis)等对该微纳米材料进行了表征, 并评价了不同混晶比材料的光催化性能. 结果表明, 所得材料是由均匀负载金红石纳米颗粒的锐钛矿纳米片组装的三维分级结构. 其具有很高的光催化活性, 分级结构和混晶异相结的同时引入是提高材料光催化活性的关键.  相似文献   

13.
采用尿素沉积法制备了Au/Ti O_2/Mo S_2等离子体复合光催化剂。通过光催化产氢实验,在10%(φ,体积分数)甘油水溶液为牺牲剂条件下,研究了不同Mo S_2含量、Au固载2%(w,质量分数)时,Au/Ti O_2/Mo S_2(ATM)复合样品的光催化产氢活性。结果表明,当Mo S_2含量为0.1%(w)时,复合样品ATM0.1显示出最高的光催化产氢活性,其产氢速率达到708.85μmol·h~(-1),是Ti O_2/Mo S_2(TM)两相复合样品中光催化活性最高样品TM6.0产氢速率的11倍。三相复合样品显示增强光催化产氢活性主要是由于吸附在Ti O_2/Mo S_2层状复合材料上的Au纳米颗粒具有表面等离子共振效应,能强烈吸收波长范围550–560 nm的可见光,诱导产生光生电子,金纳米颗粒上的电子受到激发后转移到Ti O_2导带上,Ti O_2导带上的电子传递给片状Mo S_2,最终在Mo S_2上催化氢气产生。  相似文献   

14.
Core-shell TiO2-based photocatalysts with specific composition, morphology, and functionality have attracted considerable attention for their excellent degradation properties on organic pollutants via a photocatalytic oxidation process. Herein, a N-TiO2@NH2-MIL-88(Fe) core-shell structure was prepared by coating NH2-MIL-88(Fe) on nitrogen-doped TiO2(N-TiO2) nanoparticles. Introduction of heteroatom nitrogen to pure TiO2 expands the spectral response range, leading to enhanced quantum efficiency of photocatalyst. Furthermore, loading NH2-MIL-88(Fe) on N-TiO2 improved the adsorption ability of the nanocomposites due to the porous tunnels of NH2-MIL-88(Fe). The resulted core-shell N-TiO2@NH2-MIL-88(Fe) nanocomposites realized the transfer of photo excited electrons from N-TiO2 to NH2-MIL-88(Fe) rapidly, partially reduced Fe3+ to Fe2+ in NH2-MIL-88(Fe), and further enhanced the Fenton effect on efficiently degrading methylene blue dye(MB) under visible light(λ ≥ 420 nm) with the assistance of H2O2.  相似文献   

15.
Vacuum ultraviolet irradiation coupled with photocatalytic oxidation (VUV-PCO) is an efficient and promising method for eliminating pollutants at room temperature; it involves three processes: vacuum ultraviolet (VUV) photolysis, photocatalytic oxidation (PCO), and ozone catalytic oxidation. Herein, toluene was chosen as the representative volatile organic compound (VOC), which is one of the most important precursors to form fine particulate matter and photochemical smog, because of its high toxicity and extensive existence in industries. All experiments were performed in a fixed-bed continuous-flow reactor that contained units for VUV photolysis and PCO. Mesoporous P-Mn-TiO2 was prepared by one-step hydrolysis and used as a catalyst for the oxidation of gaseous toluene under VUV irradiation through the VUV-PCO process. The as-prepared P-Mn-TiO2 samples were characterized by scanning electron microscope (SEM), transmission electron microscope (TEM), ultraviolet-visible light (UV-Vis) spectroscopy, and X-ray diffraction (XRD) analysis to determine the physicochemical properties of the catalysts and to determine the mechanisms of Mn doping and phosphoric acid modification and the effects of these processes on photocatalytic activity, ozone catalytic activity, and adsorption performance. The results indicated that the synergistic effect of phosphoric acid modification and Mn doping can improve the ozone catalytic activity and photocatalytic performance by increasing the number of oxygen active sites, completely eliminating the outlet ozone, and simultaneously promoting the efficient degradation of toluene. Moreover, doping TiO2 with Mn3+ significantly enhanced light harvesting, and numerous oxygen vacancies can be generated on the catalyst surface because of the presence of doped Mn3+ in the lattice, which adsorbs and transforms the oxygen species for toluene degradation. In addition, modification with an appropriate amount of phosphate groups can facilitate O2 and O3 adsorption on the TiO2 surface that can favor photo-induced charge carrier separation, thereby significantly improving the photocatalytic and ozone catalytic activities. The excellent catalytic performance of mesoporous P-Mn-TiO2 for toluene degradation and outlet ozone elimination was ascribed to the formation of highly reactive oxidizing species such as O(1D), O(3P), and ·OH via the catalytic decomposition of O3 adsorbed on the oxygen vacancy sites containing Mn and phosphate groups on the catalyst surface. In the VUV-PCO process, toluene was first destructed via VUV photolysis and oxidized by residual O3 generated from VUV photolysis and the active oxygen species formed in the presence of the catalyst. Finally, toluene and the generated intermediate products were oxidized and degraded to CO2 and H2O through VUV-PCO. In addition, the outlet ozone byproduct was simultaneously eliminated by the multifunctional catalyst.   相似文献   

16.
Anatase TiO2 nanospindles containing 89% exposed {101} facets (TiO2-101) and nanosheets with 77% exposed {001} facets (TiO2-001) were hydrothermally synthesized and used as supports for Pd catalysts. The effects of the TiO2 materials on the catalytic performance of Pd/TiO2-101 and Pd/TiO2-001 catalysts were investigated in the selective hydrogenation of acetylene to polymer-grade ethylene. The Pd/TiO2-101 catalyst exhibited enhanced performance in terms of acetylene conversion and ethylene yield. To understand these effects, the catalysts were characterized by H2 temperature-programmed desorption (H2-TPD), H2 temperatureprogrammed reduction (H2-TPR), transmission electron microscopy (TEM), pulse CO chemisorption, X-ray photoelectron spectroscopy (XPS), and thermogravimetric analysis (TGA). The TEM and CO chemisorption results confirmed that Pd nanoparticles (NPs) on the TiO2-101 support had a smaller average particle size (1.53 nm) and a higher dispersion (15.95%) than those on the TiO2-001 support (average particle size of 4.36 nm and dispersion of 9.06%). The smaller particle size and higher dispersion of Pd on the Pd/TiO2-101 catalyst provided more reaction active sites, which contributed to the improved catalytic activity of this supported catalyst.  相似文献   

17.
以Ce(NO3)3·6H2O、橘子皮为原料,利用共沉积法制备氧化铈水合物与橘子皮混合物(CeO2·x H2O@OPP),通过在N2中煅烧CeO2·x H2O@OPP获得CeO2@C复合材料。利用FT-IR、X射线衍射、扫描电镜、拉曼光谱、UV-Vis、X射线光电子能谱、光电流测试方法对合成材料进行了表征。结果表明,CeO2@C保留了较多的有机官能团,材料内具有较丰富的氧空穴及碳键,Ce、C、O元素均匀分布于材料内。光催化实验结果表明,在CeO2中引入碳有利于光生电子与空穴分离,提高光电流强度及光催化效率,且CeO2@C中碳含量对有机染料吸附及光催化效率影响较大。  相似文献   

18.
Nanostructured N-doped TiO2 photocatalyst has been prepared via a new approach from Ti-based MOF[NH2-MIL-125(Ti)] precursor. The success of N doping enhances light absorption and narrows the bandgap. Moreover, the as-prepared nanostructure is constructed with tiny nanoparticles and resembles a pie-like morphology inherited from the MOF, which accelerates electron transfer. Hence, as a photocatalyst for the degradation of methylene blue(MB) under visible light irradiation, the N-doped TiO2(N-TiO2) nanostructure shows higher photocatalytic activity with a reaction rate constant of 0.018 min-1 than that of the TiO2-P25 and TiO2 under the visible light.  相似文献   

19.
Titanium dioxide (TiO2)/polyacrylic acid (PAA) (TiO2/PAA) particles were formed by mixing PAA and an acidic solution of TiO2 nanoparticles in dimethylformamide (DMF) followed by heat treatment. TEM and particle analysis showed that the resulting particles had a narrow size distribution. The colloid was very stable and aggregation was not observed over a wide pH range (3–9) or at high salt concentration. The residual carboxylic acid of PAA could be modified via EDC/NHS activation to form an amide bond with a protein. An antibody was attached to the hybrid nanoparticle and specific binding to antigen was monitored by surface plasmon resonance. The results suggest that TiO2/PAA nanoparticles are candidates as the base component of a photocatalytic system with potential for substrate selectivity.  相似文献   

20.
钛酸四丁酯前驱体水热合成制备纳米TiO2颗粒,在TiO2和Vulcan XC-72活性炭复合载体上液相还原负载Pd纳米颗粒,制得Pd/TiO2/C复合催化剂. 通过透射电镜(TEM)和X射线衍射(XRD)测试表明其具有面心立方结构,Pd金属粒子(粒径约3 ~ 4 nm)均匀分散在锐钛矿型的纳米TiO2和活性炭的复合载体上. 循环伏安和计时电流曲线测试表明,与相同Pd载量的Pd/C相比,20% Pd载量的Pd/TiO2/C颗粒在常温常压下对乙醇的电催化氧化有很高活性和稳定性. 这主要归功于纳米TiO2改变了Pd表面的电子特性,且增大了其比表面积.  相似文献   

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