Ce掺杂K2La2Ti3O10催化剂的可见光高效催化制氢的研究

采用高温固相法合成了铈掺杂的K₂La₂Ti₃O₁₀催化剂, 利用X射线衍射(XRD)、紫外-可见漫反射(UV-vis DRS)、透射电镜(TEM)和X射线光电子能谱(XPS)对催化剂进行了表征. 考察了催化剂的可见光催化分解甲醇水溶液制氢的活性, 并对可见光催化机理进行了分析. 研究表明, 铈的掺杂没有改变K₂La₂Ti₃O₁₀的微晶结构, 并使催化剂粒径有所减小. 紫外可见漫反射分析表明禁带宽度为2.3 eV左右, 对可见光具有较高吸收. XPS表明La和Ti为＋3和＋4价, 而Ce则是＋3和＋4的混合价态. 担载2 wt% Pt后, 在可见光下光催化活性大大提高, 当铈的掺杂量为0.5 mol%(即Ce取代La的摩尔百分量)时, 光催化活性达到最大, 产氢速率为0.05 mmol/h; 光照5 h后产氢量为0.22 mmol, 而纯K₂La₂Ti₃O₁₀的产氢量只有0.037 mmol.     

可见光下Fe3+掺杂对K2La2Ti3O10分解水制氢性能的影响

采用溶胶-凝胶法制备了Fe3+掺杂的Fe-K2La2Ti3O10光催化剂, 并通过X射线衍射(XRD)、紫外-可见漫反射(DRS)、X射线光电子能谱(XPS)等技术对其进行了表征和分析, 考察了不同掺杂量对K2La2Ti3O10的性质及光催化分解水制氢活性的影响. 结果表明, Fe-K2La2Ti3O10在400-650 nm范围内显示强吸收, 光谱响应扩展到可见光区(λ>400 nm), 掺杂Fe3+后, K2La2Ti3O10的可见光区的光催化制氢活性显著提高, 掺杂量为nFe/nTi=0.04时活性最佳, 当催化剂用量为0.1 g, 反应液为CH3OH(30 mL)+H2O(90 mL)时, 产氢量达到1.92 μmol·h-1, 为未掺杂时的4倍.     

可见光下Fe~（3＋）掺杂对K2La2Ti3O（10）分解水制氢性能的影响

采用溶胶-凝胶法制备了Fe3+掺杂的Fe-K2La2Ti3O10.光催化剂,并通过X射线衍射(XRD)、紫外-可见漫反射(DRS)、X射线光电子能谱(XPS)等技术对其进行了表征和分析,考察了不同掺杂量对K2La2Ti3O10的性质及光催化分解水制氢活性的影响.结果表明,Fe-K2La2Ti3O10.在400-650 nm范围内显示强吸收,光谱响应扩展到可见光区(λ>400 nm),掺杂Fe3+后,K2La2Ti3O10.的可见光区的光催化制氢活性显著提高,掺杂量为nPe/nn=0.04时活性最佳,当催化剂用量为0.1 g,反应液为CH3OH(30 mL)+H2O(90 mL)时,产氢量达到1.92 μmol·h-1,为未掺杂时的4倍.     

微波辅助制备CdS插层K2La2Ti3O10复合物及其光催化制氢的性能

采用微波辅助通过酸交换、胺柱撑、离子交换等步骤制备了CdS插层的K2La2Ti3O10(记做CdS-K2La2Ti3O10)复合光催化剂.利用X射线粉末衍射(XRD),场发射扫描电子显微镜(SEM),紫外-可见漫反射吸收光谱(UV-Vis)和光致发光光谱(PL)等对产物进行表征,考察了CdS-K2La2Ti3O10在紫外光及可见光下催化制氢活性.结果表明,微波辅助法与传统法制备的插层复合催化剂晶型结构相似,同时大大减少了离子交换反应时间,减少了对层间结构的破坏,拓展了催化剂的可见光吸收范围.微波辅助制备的催化剂在紫外光和可见光照射3 h后的产氢量分别为221.53 mmol/(g cat.)和3.23 mmol/(g cat.),并对光催化机理进行了分析.     

硼族元素掺杂对K2La2Ti3O10光催化产氢性能的影响

通过溶胶.凝胶法制备了层状钙钛矿结构的K2La2Ti3O10及硼族元素掺杂的K2La2Ti3O10,采用X-射线衍射(XRD)、紫外可见漫反射光谱(DRS)等对K2La2Ti3O10及硼族元素掺杂K2La2Ti3O10进行表征.以I-为电子给体、分别在紫外和可见光辐射下研究了K2La2Ti3O10及硼族元素掺杂K2La2Ti3O10光催化分解水的产氢活性;采用第一性原理,计算了硼族元素掺杂对K2La2Ti3O10半导体能带结构和态密度的影响.从电子结构的变化揭示了掺杂引起光催化活性差异的原因.研究结果表明,硼族元素的掺入能够改善和提高K2La2Ti3O10的光解水产氢活性;在B,Al,Ga,In与Ti的物质的量的比为0.01:1的情况下,K2La2Ti3O10紫外光催化分解水产氢速率分别为151.7、119.6、155和119.2 umol·L-1·h-1,比K2La2Ti3O10掺杂改性前产氢速率分别提高了166%、110%、172%和109%,可见光分解水的产氢速率为67.0、60.5、55.0和50.0umol·L-1·h-1,分别为K2La2Ti3O10掺杂改性前产氢速率的4、3.7、3.3和3倍.     

硼掺杂对K2La2Ti3O10光催化分解水制氢活性的影响

通过溶胶-凝胶法制备了层状钙钛矿复合氧化物K2La2Ti3O10 及B掺杂的K2La2Ti3O10, 并采用X射线衍射和紫外-可见漫反射光谱等对制得样品进行了表征. 以I-为电子给体,分别在紫外和可见光辐射下研究了所制得样品光催化分解水的产氢活性; 采用第一性原理,计算了B掺杂对K2La2Ti3O10 半导体能带结构和态密度的影响,从电子结构的变化揭示了掺杂引起光催化活性差异的原因. 结果表明, B的掺入能够提高K2La2Ti3O10 的光解水产氢活性且存在合适的B掺杂浓度. 当B与Ti的摩尔比为0.01∶1时,紫外光催化分解水产氢速率为151.7 μmol/(L·h), 比未掺杂B的K2La2Ti3O10 产氢速率提高166%; 当B与Ti的摩尔比为0.02∶1时,可见光催化分解水产氢速率为85.2 μmol/(L·h), 为未掺杂B的K2La2Ti3O10 产氢速率的5.2倍.     

PbS插层K2Ti4O9催化剂：制备及光催化制氢活性

利用高温固相反应、离子交换、层间插入反应和硫化处理制备了PbS插层的K2Ti4O9催化剂。利用XRD、TEM、SEM、XRF、PL和紫外-可见漫反射光谱对催化剂进行了表征,考察了催化剂紫外光和可见光光催化制氢活性。结果表明,制备的PbS插层K2Ti4O9催化剂对可见光的吸收范围较宽,其吸收边界约为710 nm,在紫外光和可见光下3 h累积产氢量可达到115.46 mmol.gcat-1和0.92 mmol.gcat-1,与CdS插层K2Ti4O9催化剂相比具有更高的催化活性。     

CdS插层的K4Nb6-xCuxO17复合物的制备及其光催化制氢活性

以Nb2O5,K2CO3和CuO为原料经高温固相反应合成K4Nb6-xCuxO17催化剂,并通过层间离子交换反应,胺插入反应以及硫化反应制备CdS插层K4Nb6-xCuxO17复合催化剂(K4Nb6-xCuxO17/CdS)。利用X射线衍射(XRD),X射线光电子能谱(XPS),场发射扫描电镜(SEM),X射线能谱仪(EDX),紫外-可见漫反射(UV-Vis),分子荧光光谱(PL)等技术对催化剂进行表征。考察了催化剂的可见光催化制氢活性。结果表明,Cu离子掺杂进入K4Nb6O17晶格中,CdS位于K4Nb6O17层间。CdS插层K4Nb6-xCuxO17催化剂的最大吸收光波长约为550 nm。催化剂制氢活性有明显提高,紫外光和可见光下3 h产氢量分别达到279.83 mmol.gcat-1和7.11 mmol.gcat-1。最后讨论了复合催化剂光生电荷转移机理。     

Cu/Sr3Ti2O7的制备及其光催化分解水制氢活性

采用聚合合成法(PCM)合成出层状钙钛矿结构的Sr3Ti2O7, 进而负载Cu 离子, 制成Cu/Sr3Ti2O7催化剂. 以超纯水和甲醇牺牲剂体系的光催化分解反应为探针, 通过检测氢气生成速率评价了催化剂的光催化性能, 并借助光电子能谱(XPS)、X 射线衍射(XRD)分析、紫外-可见漫反射光谱(UV-Vis DRS)等手段对催化剂进行了表征. 实验结果表明, Cu 在催化剂中以多价态存在, Cu+和吸附氧有利于光生电子的转移. Cu/Sr3Ti2O7催化剂较之纯Sr3Ti2O7催化剂活性大大提高, Cu 最佳负载量为1.5%(w). 产氢速率可稳定在550-600 μmol·h-1. 还原过的Cu/Sr3Ti2O7催化剂产氢速率最高可达1140.8 μmol·h-1.     

Synthesis of CdSpillared K2La2Ti3Olo Catalyst via a Microwave Assisted Process and Its Photocatalytic Property

采用微波辅助通过酸交换、胺柱撑、离子交换等步骤制备了CdS插层的K2La2Ti3010（ia做CdS-K2La2Ti3010）复合光催化剂．利用x射线粉末衍射（xgo）,场发射扫描电子显微镜（SEM）,紫外一可见漫反射吸收光谱（UV-Vis）和光致发光光谱（PL）等对产物进行表征,考察了CdS．KzLa2Ti3010在紫外光及可见光下催化制氢活性．结果表明,微波辅助法与传统法制备的插层复合催化剂晶型结构相似,同时大大减少了离子交换反应时间,减少了对层间结构的破坏,拓展了催化剂的可见光吸收范围．微波辅助制备的催化剂在紫外光和可见光照射3h后的产氢量分别为221．53mmol／（gcat．）和3．23mmol／（gcat．）,并对光催化机理进行了分析．     

Preparation of Pt/K_2La_2Ti_3O_(10) and its photo-catalytic activity for hydrogen evolution from methanol water solution

1 Introduction Conventional energy resources, such as coal, petro-leum products, etc., which are fulfilling most of the world’s energy requirement have been depleted to a great extend. The human being is now facing exhaus-tion of fuel resources in a near…     

Photocatalytic hydrogen production from water over M-doped La2Ti2O7 (M = Cr, Fe) under visible light irradiation (lambda > 420 nm)

In the search for efficient photocatalysts working under visible light, we have investigated the effect of cation substitution on a layered perovskite, La2Ti2O7. Among various metal dopants, only Cr and Fe induced intense absorption of visible light (lambda > 400 nm), and only these catalysts produced H2 photocatalytically from water in the presence of methanol under visible light irradiation (lambda > 420 nm). The polymerized complex method was found to be more efficient for fabrication of the present catalysts producing a more homogeneous structure than the solid-state reaction. The characterization by XRD, UV-vis DRS, XPS, and XANES revealed that doped Cr and Fe were present in the Cr3+ and Fe3+ states substituting for Ti sites in the La2Ti2O7 lattice. The theoretical calculation indicated that the most significant feature in the electronic band structure of the metal-doped La2Ti2O7 was the formation of a partially filled 3d band in the band gap of La2Ti2O7, while the contribution of these dopants on the valence band was negligible. Excitation of electrons from this localized interband to the conduction band of La2Ti2O7 was responsible for visible light absorption and the H2 evolution from water under visible light.     

Photoluminescence of perovskite nanosheets prepared by exfoliation of layered oxides, K2Ln2Ti3O10, KLnNb2O7, and RbLnTa2O7 (Ln: lanthanide ion)

Luminescent perovskite nanosheets were prepared by exfoliation of single- or double-layered perovskite oxides, K2Ln2Ti3O10, KLnNb2O7, and RbLnTa2O7 (Ln: lanthanide ion). The thickness of the individual nanosheets corresponded to those of the perovskite block in the parent layered compounds. Intense red and green emissions were observed in aqueous solutions with Gd1.4Eu0.6Ti3O10- and La0.7Tb0.3Ta2O7-nanosheets, respectively, under UV illumination with energies greater than the corresponding host oxide band gap. The coincidence of the excitation spectrum and the band gap absorbance indicates that the visible emission results from energy transfer within the nanosheet. The red emission intensity of the Gd1.4Eu0.6Ti3O10-nanosheets was much stronger than that of the La0.90Eu0.05Nb2O7-nanosheets reported previously. The strong emission intensity is a result of a two-step energy transfer cascade within the nanosheet from the Ti-O network to Gd(3+) and then to Eu(3+). The emission intensities of the Gd1.4Eu0.6Ti3O10- and La0.7Tb0.3Ta2O7-nanosheets can be modulated by applying a magnetic field (1.3-1.4 T), which brings about a change in orientation of the nanosheets in solution. The emission intensities increased when the excitation light and the magnetic field directions were perpendicular to each other, and they decreased when the excitation and magnetic field were collinear and mutually perpendicular to the direction of detection of the emitted light.     

Selective catalytic oxidation of NO with O2 over Ce-doped MnOx/TiO2 catalysts

A series of Ce-doped MnOx/TiO2 catalysts were prepared by impregnation method and used for catalytic oxidation of NO in the presence of excess O2. The sample with the Ce doping concentration of Ce/Mn=1/3 and calcined at 300°C shows a superior activity for NO oxidation to NO2. On Ce(1)Mn(3)Ti catalyst, 58% NO conversion was obtained at 200°C and 85% NO conversion at 250°C with a GHSV of 41000 h-1, which was much higher than that over MnOx/TiO2 catalyst (48% at 250°C). Characterization results implied that the higher activity of Ce(1)Mn(3)Ti could be attributed to the enrichment of well-dispersed MnOx on the surface and the abundance of Mn3+ and Ti3+ species. The addition of Ce into MnOx/TiO2 could improve oxygen storage capacity and facilitate oxygen mobility of the catalyst as shown by PL and ESR, so that its activity for NO oxidation could be enhanced. The effect of H2O and SO2 on the catalyst activity was also investigated.     

La_2Ti_6O_(15)-CeTi_(21)O_(38)-PbTiO_3 ceramics formed in gaseous penetration of La-Ce into PbTiO_3 and their electric properties

PbTiO3 ceramics, which are typical ferroelectric materials, are useful in various applied fields. For example, it has a very good candidacy for piezoelectric materials for high temperature and high sensibility. In recent years, the studies on doped PbTiO3 ceramics have received consid-erable attention[1—3]. The modified PbTiO3 ceramics doped with Ca2+, Sm3+, Y3+, Ce4+ etc. have some better properties: their Curies temperature decreases, their tetragonal distortion degree de-grades and th…     

K_4Ce_2Ta_(10-x)Nb_xO_(30)-WO_3复合物的光催化储能特性

为获得可见光响应的储能光催化材料,以离子交换法获得的钨酸溶液与可见光响应光催化剂K4Ce2Ta10-xNbxO30(x=0,5,10)为原料,制备了K4Ce2Ta10-xNbxO30-WO3(x=0,5,10)复合光催化剂。采用XRD,TEM,BET,UV-V is等方法表征了材料的物理化学特性,通过电化学方法和抗菌实验对其储能特性进行表征,分析和研究了K4Ce2Ta10-xNbxO30能带结构对其光催化储能效应的影响及作用机制。研究结果表明,稀土元素Ce贡献于K4Ce2Ta10-xNbxO30能带结构的调变,使得K4Ce2Ta10-xNbxO30-WO3复合光催化材料具有可见光储能特性,在黑暗中也显示出一定的储能抗菌效应。该材料的储能性能受Nb含量和K4Ce2Ta10-xNbxO30的导带位置的影响:随着Nb含量的增加,光生电子还原能力下降,导致储能性能降低。     

Reversible cation/anion extraction from K2La2Ti3O10: formation of new layered titanates, KLa2Ti3O9.5 and La2Ti3O9

A new soft-chemical transformation of layered perovskite oxides is described wherein K2O is sequentially extracted from the Ruddlesden-Popper (R-P) phase, K2La2Ti3O10 (I), yielding novel anion-deficient KLa2Ti3O(9.5) (II) and La2Ti3O9 (III). The transformation occurs in topochemical reactions of the R-P phase I with PPh4Br and PBu4Br (Ph = phenyl; Bu = n-butyl). The mechanism involves the elimination of KBr accompanied by decomposition of PR4+ (R = phenyl or n-butyl) that extracts oxygen from the titanate. Analysis of the organic products of decomposition reveals formation of Ph3PO, Ph3P, and Ph-Ph for R = phenyl, and Bu3PO, Bu3P along with butane, butene, and octane for R = butyl. The inorganic oxides II and III crystallize in tetragonal structures (II: P4/mmm, a = 3.8335(1) A, c = 14.334(1) A; III: I4/mmm, a = 3.8565(2) A, c = 24.645(2) A) that are related to the parent R-P phase. II is isotypic with the Dion-Jacobson phase, RbSr2Nb3O10, while III is a unique layered oxide consisting of charge-neutral La2Ti3O9 anion-deficient perovskite sheets stacked one over the other without interlayer cations. Interestingly, both II and III convert back to the parent R-P phase in a reaction with KNO3. While transformations of the R-P phases to other related layered/three-dimensional perovskite oxides in ion-exchange/metathesis/dehydration/reduction reactions are known, the simultaneous and reversible extraction of both cations and anions in the conversions K2La2Ti3O10 right harpoon over left harpoon KLa2Ti3O9.5 right harpoon over left harpoon La2Ti3O9 is reported here for the first time.