Pt/TiO2上的污染物降解耦合光解水制氢研究

以三乙胺和乙醚为目标污染物,研究了Pt/TiO₂上光催化分解水产氢和污染物同时降解的光催化反应。研究了作为电子给体的污染物浓度对光解水制氢反应的影响,污染物本身的降解规律符合Langmuir-Hinshelwood准一级动力学方程。使用拉曼光谱仪和紫外-可见光分光光度计对降解产物浓度进行了表征,讨论了可能的降解反应机理。     

Construction of highly efficient 0D/2D Bi2MoO6/g-C3N4 heterojunctions for visible-light-driven photodegradation of 1-naphthol

Photocatalytic degradation is an ecologically benign method of reducing organic contaminants in wastewater. To remove the pollutant 1-naphthol, highly efficient 0D/2D Bi₂MoO₆/g-C₃N₄ heterojunctions were successfully assembled by a one-step hydrothermal method, where zero-dimension (0D) Bi₂MoO₆ nanoparticles were firmly bonded to two-dimension (2D) g-C₃N₄ nanosheets. 0D/2D Bi₂MoO₆/g-C₃N₄ exhibited exceptional degradation efficiency for 1-naphthol with a removal rate of 81.5% after 60 min of visible light irradiation. The enhanced photocatalytic ability was attributed to the matched band structures and tightly connected heterojunctions, which effectively prevented the recombination of photogenerated carriers. Besides, the photodegradation mechanism was revealed by investigating the catalysts' crystal phase, morphology, physicochemical and optical properties. This work introduces a novel method for one-step preparation of 0D/2D photocatalysts and advances the utilization of photodegradation for organic pollutants.     

Low-temperature synthesis one-dimensional Ag2CO3/SnFe2O4 Z-scheme with excellent visible-light photoactivity

In this study, Ag₂CO₃/SnFe₂O₄ (Ag₂CO₃/SFO) photocatalyst was prepared by a simple hydrothermal-ultrasonic method for the efficient degradation of ciprofloxacin and phenol. The SFO nanoparticles were attached on the surface of Ag₂CO₃ rods synthesized by a low-temperature precipitation method, resulting a unique 1D/0D morphology, which increased the number of active sites. Due to introduction of magnetic SFO, Ag₂CO₃/SFO exhibited excellent magnetic recovery performance. When the mass fraction of SFO was 5%, the degradation efficiency of composite photocatalyst was the highest, the degradation rate for ciprofloxacin was 6.5 and 1.5 times higher than pure SFO and Ag₂CO₃, respectively. The improved photoactivity of Ag₂CO₃/SFO should be attributed to the construction of heterojunction with tight interface, which boosts the separation and transfer of photoinduced electron and hole pairs. On the basis of experimental results, a possible Z-scheme photocatalytic mechanism was discussed. Additionally, the excellent photostability of Ag₂CO₃/SFO was proved by a cycle experiment.     

自搅拌下CoB/SiO2催化剂催化硼氢化钠水解制氢研究

采用浸渍-化学还原法制备了硼化钴/二氧化硅（CoB/SiO₂）催化剂,并考察了其催化硼氢化钠水解制氢的性能。研究了二氧化硅粒径、硝酸钴与二氧化硅物质的量比、硝酸钴与硼氢化钠物质的量比等条件对催化剂性能的影响,进而考察了催化剂用量、搅拌转速、反应温度等条件对硼氢化钠水解制氢性能的影响。结果表明,在二氧化硅粒径为15 nm、硝酸钴与二氧化硅物质的量比为0.08∶1、硝酸钴与硼氢化钠物质的量比为1∶5条件下,制备的催化剂催化硼氢化钠水解产氢的速率为45.6 mL/（min·g）;因为催化剂粒径很小,伴随硼氢化钠水解产氢产生的动量可以完全消除外扩散速率的影响,搅拌转速对硼氢化钠水解速率的影响很小,硼氢化钠的水解速率随着催化剂用量的增加而增大;随着温度的升高,硼氢化钠的水解速率增大,硼氢化钠水解反应的表观活化能为48.54 kJ/mol,硼氢化钠反应级数为零;催化剂具有良好的重复使用性能和稳定性。     

Rational design of MoS2/g-C3N4/ZnIn2S4 hierarchical heterostructures with efficient charge transfer for significantly enhanced photocatalytic H2 production

The rational design of hierarchical heterojunction photocatalysts with efficient spatial charge separation remains an intense challenge in hydrogen generation from photocatalytic water splitting. Herein, a noble-metal-free MoS₂/g-C₃N₄/ZnIn₂S₄ ternary heterostructure with a hierarchical flower-like architecture was developed by in situ growth of 3D flower-like ZnIn₂S₄ nanospheres on 2D MoS₂ and 2D g-C₃N₄ nanosheets. Benefiting from the favorable 2D-2D-3D hierarchical heterojunction structure, the resultant MoS₂/g-C₃N₄/ZnIn₂S₄ nanocomposite loaded with 3 wt% g-C₃N₄ and 1.5 wt% MoS₂ displayed the optimal hydrogen evolution activity (6291 μmol g^?1 h^?1), which was a 6.96-fold and 2.54-fold enhancement compared to bare ZnIn₂S₄ and binary g-C₃N₄/ZnIn₂S₄, respectively. Structural characterizations reveal that the significantly boosted photoactivity is closely associated with the multichannel charge transfer among ZnIn₂S₄, MoS₂, and g-C₃N₄ components with suitable band-edge alignments in the composites, where the photogenerated electrons migrate from g-C₃N₄ to ZnIn₂S₄ and MoS₂ through the intimate heterojunction interfaces, thus enabling efficient electron-hole separation and high photoactivity for hydrogen evolution. In addition, the introduction of MoS₂ nanosheets highly benefits the improved light-harvesting capacity and the reduced H₂-evolution overpotential, further promoting the photocatalytic H₂-evolution performance. Moreover, the MoS₂/g-C₃N₄/ZnIn₂S₄ ternary heterostructure possesses prominent stability during the photoreaction process owing to the migration of photoinduced holes from ZnIn₂S₄ to g-C₃N₄, which is deemed to be central to practical applications in solar hydrogen production.     

Enhanced photocatalytic hydrogen evolution over TiO2/g-C3N4 2D heterojunction coupled with plasmon Ag nanoparticles

2D heterojunction based on g-C₃N₄ nanosheets with other semiconductor nanosheets is a promising way to improve photocatalytic hydrogen evolution (PHE) activity over g-C₃N₄. However, current 2D heterojunction based on g-C₃N₄ are unsatisfactory due to their insufficient absorption of visible light and inefficient charge separation. In this work, Ag/TiO₂/g-C₃N₄ nanocomposites based on 2D heterojunction coupling with Ag surface plasmon resonance (SPR) were synthesized by a method combining facile wetness impregnation calcination. The PHE activity of Ag/TiO₂/g-C₃N₄ nanocomposites is attributed to the TiO₂/g-C₃N₄ 2D heterojunction and bare g-C₃N₄ nanosheet under visible light irradiation, indicating a cooperative effect between Ag and TiO₂/g-C₃N₄ 2D heterojunction. As a result of SPR effect, the composites strongly absorb visible light. In addition, the oscillating hot electrons from Ag can easily transfer to 2D heterojunction. This synergistic effect lead to sufficient visible light absorption and efficient charge separation of 2D heterojunction, which improved the PHE activity of g-C₃N₄. This work indicates that loading metal nanoparticles on 2D heterojunction as metal SPR-2D heterojunction nanocomposites may be a potential method for harvesting visible light for PHE.     

Hydrogen production from ethanol over bimetallic Rh-M/CeO2 (M = Pd or Pt)

The reaction of ethanol for the production of hydrogen has been studied over a series of metal supported CeO₂ catalysts. The study is conducted by TPD, steady state reaction, XPS, TEM, and infrared spectroscopy. TPD gave evidence for the role of Rh in dissociating the carbon–carbon bond needed for efficient production of hydrogen molecules. IR of CO adsorption at 90 K revealed that Rh particles are most likely in very small clusters as evidenced by a single OC–Rh IR band at 2020 cm⁻¹. TEM did not show conclusive evidence for the presence of the metal on-top of the CeO₂ support, yet the Rh-Pd/CeO₂ used catalyst has features that might be attributed to epitaxial growth of the noble metal along the (1 1 1) surface of the CeO₂ support. Considerable reconstruction of the CeO₂ support is seen for the used catalysts, in addition. Reforming of ethanol to hydrogen using (3 moles of water per mole of ethanol) was very efficient particularly above 650 K where hydrogen selectivity reaches 60 vol.%. At these temperatures hydrogen production from reforming of methane takes place.     

CdS nanoparticles decorated hexagonal Fe2O3 nanosheets with a Z-scheme photogenerated electron transfer path for improved visible-light photocatalytic hydrogen production

Photocatalytic water splitting for hydrogen production (H₂) is one of the main potential applications of photocatalytic technology, which can use solar energy as the energy required for chemical reactions to alleviate the energy crisis. In this work, zero-dimensional/two-dimensional (0D/2D) contact surface CdS/α-Fe₂O₃ (CF) heterojunction photocatalyst was synthesized via a simple solvothermal method. Photocatalytic hydrogen production experiments revealed that the CF-15 sample shows the optimal photocatalytic H₂ rate (1806 (μmol·h^-1·g^-1)) and apparent quantum efficiency (AQE = 13.7% at λ = 420 nm). The enhancement of photocatalytic performance is mainly attributed to the contact of 0D/2D interface and the synergistic effect of Z-scheme electron transfer mechanism. This work provides an effective way for modified composite semiconductor photocatalyst by constructing special interface heterojunction to achieve highly efficiently catalysis.     

Enhancing Effect of H2 on the Selective Reduction of NO with CO over Ba-doped Ir/WO3/SiO2 Catalyst

In order to improve the catalytic performance of supported-Ir catalysts for the selective reduction of NO with CO, the effect of H₂ was investigated. While adding H₂ showed no or negative effect on NO conversion on Ir/SiO₂, Ba/Ir/SiO₂ and Ir/WO₃/SiO₂ catalysts, the activity of Ba-doped Ir/WO₃/SiO₂ catalyst for NO reduction was significantly increased by H₂ addition. The role of H₂ was found to stabilize the catalytically active Ir-WO _x sites during the reaction.     

From single crystals to supported nanoparticles in experimental and theoretical studies of H2 oxidation over platinum metals (Pt, Pd): Intermediates, surface waves and spillover

The present paper reviews our investigations concerning the mechanism of H₂ + O₂ reaction on the metal surfaces (Pt, Pd) at different structures: single crystals (Pt(1 1 1), Pt(1 0 0), Pd(1 1 0)); microcrystals (Pt tips); and nanoparticles (Pd–Ti³⁺/TiO₂). Field electron microscopy (FEM), field ion microscopy (FIM), high-resolution electron energy loss spectroscopy (HREELS), XPS, UPS, work function (WF), TDS and temperature-programmed reaction (TPR) methods have been applied to study the kinetics of H₂ oxidation on a nanolevel. The adsorption of both O₂ and H₂ and several dissociative products (H_ads, O_ads, OH_ads) was studied by HREELS. Using the DFT technique the equilibrium states and stretching vibrations of H, O, OH, H₂O, adsorbed on the Pt(1 1 1) surface, have been calculated depending on the surrounding of the metal atoms. Sharp tips of Pt, several hundreds angstroms in radius, were used to perform in situ investigations of the dynamic surface processes. The FEM and FIM studies on the Pt-tip surface demonstrate that the self-oscillations and waves propagations are connected with periodic changes in the surface structure of nanoplane (1 0 0)-(hex) ↔ (1 × 1), varying the catalytic property of metal. The role of defects (Ti³⁺-□_O) in the adsorption centers formation, their stabilization by the palladium nanoparticles, and then the defects participation in H₂ + O₂ steady-state reaction over Pd–Ti³⁺/TiO₂ surface have been studied by XPS, UPS and photodesorption techniques (PhDS). This reaction seems to involve the “protonate” hydrogen atoms (H⁺/TiO_x) as a result of spillover effect: diffusion of H_ads atoms from Pd particles on a TiO_x surface. The comprehensive study of H₂, O₂ adsorption and H₂ + O₂ reaction in a row: single crystals → tips → nanoparticles has shown the same nature of active centers over these metal surfaces.     

How to control the selectivity in the reduction of NOx with H2 over Pt-Ba/Al2O3 Lean NOx Trap catalysts

The reduction process of NO_x species stored over Pt-Ba/Al₂O₃ Lean NO_x Trap systems is analysed in this paper when H₂ is used as a reductant. The effect of different experimental conditions (temperature, reductant concentration, adsorption lengths, etc.) is addressed and discussed in relation to the selectivity and the efficiency of the reduction process.     

H4GeW12O40/Cu3(BTC)2催化Biginelli反应合成3,4-二氢嘧啶-2(1H)-酮衍生物

采用浸渍法以金属有机骨架Cu_3(BTC)_2负载锗钨酸(H_4GeW_(12)O_(40))制备H4Ge W_(12)O_(40)/Cu_3(BTC)_2催化剂,并用该催化剂催化芳醛、尿素和乙酰乙酸乙酯通过"一锅法"Biginelli缩合反应,以无水乙醇为溶剂,合成6种3,4-二氢嘧啶-2(1H)-酮衍生物;通过熔点的测定,IR,1H NMR和MS等对产物3,4-二氢嘧啶-2(1H)-酮衍生物进行表征。结果表明:在芳醛用量为0.04 mol,n(芳醛)∶n(乙酰乙酸乙酯)∶n(尿素)=1∶1.5∶1.5,催化剂的用量占反应物料总质量的4.0%,反应温度为90℃,反应时间为90 min的条件下,目标产物收率可达63.0%~76.3%。     

Variation of discharge capacities with C-rate for LiNi1−yMyO2 (M = Ni,Ga, Al and/or Ti) cathodes synthesized by the combustion method

LiNiO₂, LiNi_0.995Al_0.005O₂, LiNi_0.975Ga_0.025O₂, LiNi_0.990Ti_0.010O₂ and LiNi_0.990Al_0.005Ti_0.005O₂ specimens were synthesized by preheating at 400 °C for 30 min in air and calcination at 750 °C for 36 h in an O₂ stream. The variation of the discharge capacities with C-rate for the synthesized samples was investigated. LiNi_0.990Al_0.005Ti_0.005O₂ has the largest first discharge capacities at the 0.1 and 0.2 C rates. LiNi_0.990Ti_0.010O₂ has the largest first discharge capacity at the 0.5 C rate. In case of LiNiO₂ and LiNi_0.990Ti_0.010O₂, the first discharge capacity decreases slowly as the C-rate increases. LiNiO₂ has the largest discharge capacities at n = 10 (after stabilization of the cycling performance) at the 0.1, 0.2 and 0.5 C rates. This is considered to be related with the largest value of I_0 0 3/I_1 0 4 and the smallest value of R-factor (the least degree of cation mixing) among all the samples. LiNi_0.975Ga_0.025O₂ exhibits the lowest discharge capacity degradation rates at 0.1, 0.2 and 0.5 C rates.