Hydrogen sulfide (H₂S) is a well-known toxic gas with the smell of rotten eggs. Since the first description of the toxicity of H₂S in 1713, most studies about H₂S have been devoted to its toxic effects. Recently, H₂S has been proposed as a physiologically active messenger. Three groups discovered that the brain contains relatively high concentrations of endogenous H₂S. This discovery accelerated the identification of an H₂S-producing enzyme, cystathionine β-synthase (CBS) in the brain. In addition to the well-known regulators for CBS, S-adenosyl-L-methionine (SAM) and pyridoxal-5′-phosphate, it was recently found that Ca²⁺/calmodulin-mediated pathways are involved in the regulation of CBS activity. H₂S is produced in response to neuronal excitation, and alters hippocampal long-term potentiation (LTP), a synaptic model for memory. can also regulate the release of corticotropin-releasing hormone (CRH) from hypothalamus. Another H₂S producing enzyme, cystathionine γ-lyase (CSE), has been identified in smooth muscle, and H₂S relaxes smooth muscle in synergy with nitric oxide (NO). Recent progress in the study of H₂S as a novel neuromodulator/transmitter in the brain is briefly reviewed.]]>

2S、含CO₂的特点。建设处理规模120×10⁸ m³/a的天然气净化厂，面临天然气净化难度大、硫磺储运技术和安全要求高、生产工艺及安全控制复杂等诸多技术难题。目前国内尚无百亿立方米级天然气净化以及配套硫磺成型与安全储运技术。为此，在优选评价国内外先进净化工艺的基础上，确定了适合普光气田的高含硫天然气净化工艺，并首次应用了气相固定床水解COS、中间胺液冷却、MAG-液硫脱气、特大型火炬放空、液硫湿法成型等国际先进工艺和专利技术。开发了国内首例特大型散装硫磺料仓、首例5 000 m³液硫储罐、首套硫磺流水线转运以及快速定量装车系统，实现200×10⁴ t/a硫磺储运系统的全方位实时监控和安全运行。配套开发先进、灵活、可靠的生产过程控制与安全控制系统，确保整个净化厂处于安全、有效的受控状态。高含硫天然气净化关键技术应用于普光气田后，装置运行平稳，产品质量合格，各项安全保障到位。为其他大型高酸性气田的天然气净化提供了示范和借鉴。]]>

Reaction pathways for the acid-catalyzed conversion of furfuryl alcohol (FAL) to ethyl levulinate (EL) in ethanol were investigated using liquid chromatography-mass spectrometry (LC-MS), 1D and 2D nuclear magnetic resonance (NMR) spectroscopy, and ab initio high-level quantum chemical (G4MP2) calculations. Our combined studies show that the production of EL at high yields from FAL is not accompanied by stoichiometric production of diethyl either (DEE), indicating that ethoxymethyl furan (EMF) is not an intermediate in the major reaction pathway. Several intermediates were observed using an LC-MS system, and three of these intermediates were isolated and subjected to reaction conditions. The structures of two intermediates were elucidated using 1D and 2D NMR techniques. One of these intermediates is EMF, which forms EL and DEE in a secondary reaction pathway. The second intermediate identified is 4,5,5-triethoxypentan-2-one, which is analogous to one of the intermediates observed in the conversion of FAL to LA in water (i.e. 4,5,5-trihydroxypentan-2-one). Furthermore, conversion of this intermediate to EL again involves the formation of DEE, indicating that it is also part of a secondary pathway. The primary pathway for production of EL involves solvent-assisted transfer of a water molecule from the partially detached protonated hydroxyl group of FAL to a ring carbon, followed by intra-molecular hydrogen shift, where the apparent reaction barrier for the hydrogen shift is relatively smaller in ethanol (21.1 kcal/mol) than that in water (26.6 kcal/mol).

Highly monodispersed nitrogen doped TiO2 nanoparticles were successfully deposited on graphene (N-TiO2/Gr) by a facile in-situ wet chemical method for the first time. N-TiO2/Gr has been further used for photocatalytic hydrogen production using a naturally occurring abundant source of energy i.e. solar light. The N-TiO2/Gr nanocomposite composition was optimized by varying the concentrations of dopant nitrogen and graphene (using various concentrations of graphene) for utmost hydrogen production. The structural, optical and morphological aspects of nanocomposites were studied using XRD, UV-DRS, Raman, XPS, FESEM, and TEM. The structural study of the nanocomposite shows existence of anatase N-TiO2. Further, the details of the components present in the composition were confirmed with Raman and XPS. The morphological study shows that very tiny, 7-10 nm sized, N-TiO2 nanoparticles are deposited on the graphene sheet. The optical study reveals a drastic change in absorption edge and consequent total absorption due to nitrogen doping and presence of graphene. Considering the extended absorption edge to the visible region, these nanocomposites were further used as a photocatalyst to transform hazardous H2S waste into eco-friendly hydrogen using solar light. The N-TiO2/Gr nanocomposite with 2% graphene exhibits enhanced photocatalytic stable hydrogen production i.e. approximately 5941 mumol h(-1) under solar light irradiation using just 0.2 gm nanocomposite, which is much higher as compared to P25, undoped TiO2 and TiO2/Gr nanocomposite. The enhancement in the photocatalytic activity is attributed to 'N' doping as well as high specific surface area and charge carrier ability of graphene. The recycling of the photocatalyst shows a good stability of the nanocomposites. This work may provide new insights to design other semiconductor deposited graphene novel nanocomposites as a visible light active photocatalyst.

A novel, facile self-driven photoelectrocatalytic (PEC) system was established for highly selective and efficient recovery of H2S and simultaneous electricity production. The key ideas were the self-bias function between a WO3 photoanode and a Si/PVC photocathode due to their mismatched Fermi levels and the special cyclic redox reaction mechanism of I(-)/I3(-). Under solar light, the system facilitated the separation of holes in the photoanode and electrons in the photocathode, which then generated electricity. Cyclic redox reactions were produced in the photoanode region as follows: I(-) was transformed into I3(-) by photoholes or hydroxyl radicals, H2S was oxidized to S by I3(-), and I3(-) was then reduced to I(-). Meanwhile, H(+) was efficiently converted to H2 in the photocathode region. In the system, H2S was uniquely oxidized to sulfur but not to polysulfide (Sx(n-)) because of the mild oxidation capacity of I3(-). High recovery rates for S and H2 were obtained up to approximately 1.04 mg h(-1) cm(-1) and approximately 0.75 mL h(-1) cm(-1), respectively, suggesting that H2S was completely converted into H2 and S. In addition, the output power density of the system reached approximately 0.11 mW cm(-2). The proposed PEC-H2S system provides a self-sustaining, energy-saving method for simultaneous H2S treatment and energy recovery.

As a green and sustainable technology, semiconductor-based heterogeneous photocatalysis has received much attention in the last few decades because it has potential to solve both energy and environmental problems. To achieve efficient photocatalysts, various hierarchical semiconductors have been designed and fabricated at the micro/nanometer scale in recent years. This review presents a critical appraisal of fabrication methods, growth mechanisms and applications of advanced hierarchical photocatalysts. Especially, the different synthesis strategies such as two-step templating, in situ template-sacrificial dissolution, self-templating method, in situ template-free assembly, chemically induced self-transformation and post-synthesis treatment are highlighted. Finally, some important applications including photocatalytic degradation of pollutants, photocatalytic H2 production and photocatalytic CO2 reduction are reviewed. A thorough assessment of the progress made in photocatalysis may open new opportunities in designing highly effective hierarchical photocatalysts for advanced applications ranging from thermal catalysis, separation and purification processes to solar cells.

This critical review shows the basis of photocatalytic water splitting and experimental points, and surveys heterogeneous photocatalyst materials for water splitting into H2 and O2, and H2 or O2 evolution from an aqueous solution containing a sacrificial reagent. Many oxides consisting of metal cations with d0 and d10 configurations, metal (oxy)sulfide and metal (oxy)nitride photocatalysts have been reported, especially during the latest decade. The fruitful photocatalyst library gives important information on factors affecting photocatalytic performances and design of new materials. Photocatalytic water splitting and H2 evolution using abundant compounds as electron donors are expected to contribute to construction of a clean and simple system for solar hydrogen production, and a solution of global energy and environmental issues in the future (361 references).

6,13-Pentacenequinone (PQ), an intermediate for an organic semiconductor pentacene, was synthesized by single step solvent free solid state reaction at room temperature under ambient conditions which is hitherto unattempted. The phase purity has been confirmed by XRD and NMR. Optical study showed the absorption at 390 and 412 nm attributed to the pi-pi* and n-pi* transitions, respectively. Cyclic voltammetry indicates the semiconducting nature of PQ having a band gap of 3 eV. The photoluminescence study revealed emissions at 408 and 432 nm. Considering the good thermal stability and absorption well within visible region, wisely, PQ has been used as a photocatalyst for the hydrogen production under solar light. Surprisingly we observed the utmost hydrogen evolution i.e. 4848 mumol/h/0.1 g (quantum efficiency 6.8%). The repeatability and reusability study confirmed the stability of the photocatalyst. The confirmation of the photocatalytic effect was also confirmed using methylene blue (MB) dye degradation under natural sunlight. The observed rate constant (Kapp) for photocatalytic MB degradation was 1.60 x 10(-2) min(-1). The use of an organic photocatalyst for hydrogen production has been demonstrated for the first time. This novel organic photocatalyst can also be explored for water splitting.

Nitrogen-doped TiO2 nanostructures in the form of marigold flowers have been synthesized for the first time using a facile solvothermal method. The structural analysis has shown that such an N-doped TiO2 system crystallizes in the anatase structure. The optical absorption spectra have clearly shown the shift in the absorption edge towards the visible-light range, which indicates successful nitrogen doping. The nitrogen doping has been further confirmed by photoluminescence and photoemission spectroscopy. Microscopy studies have shown the thin nanosheets (petals) of N-TiO2 with a thickness of similar to 2-3 nm, assembled in the form of the marigold flower with a high surface area (224 m(2) g(-1)). The N-TiO2 nanostructure with marigold flowers is an efficient photocatalyst for the decomposition of H2S and production of hydrogen under solar light. The maximum hydrogen evolution obtained is higher than other known N-TiO2 systems. It is noteworthy that photohydrogen production using the unique marigold flowers of N-TiO2 from abundant H2S under solar light is hitherto unattempted. The proposed synthesis method can also be utilized to design other hierarchical nanostructured N-doped metal oxides.

It is quite well-known that refineries are producing huge amount of H2S which has been used to produce sulphur and water using the well-known Claus process. This process is not an economically viable process, due to the high-cost chemical process and creates further acute environmental problems. Therefore, we have demonstrated the conversion of poisonous H2S into H-2 using an ecofriendly phocatalysis process which is a green unconventional energy source. We have investigated ecofriendly nanostructured ZnIn2S4 photocatalyst to produce hydrogen from H2S using solar light. We also demonstrate the controlled synthesis of hierarchical nanostructured ZnIn2S4 using a facile hydrothermal method. The morphologies obtained have been greatly influenced by the presence of triethylamine (TEA) with various concentrations during the reaction. Surprisingly, a highly crystalline hexagonal layer structured ZnIn2S4 was obtained instead of cubic spinel. The hierarchical nanostructure, i.e. marigold flower-like morphology, was obtained without any surfactant. The thin and transparent petals self-assembled to form the unique nanostructured marigold flower. The highly crystalline puffy marigold flowers and nanoplates/nanostrips were obtained using TEA-assisted hydrothermal synthesis. Optical study shows the band gap in the range of 2.34-2.48 eV. Considering the band gap in the visible region, ZnIn2S4 is used as photocatalyst for hydrogen production from hydrogen sulphide under solar light which is hitherto unattempted. The constant photocatalytic activity of hydrogen evolution, i.e. 5287 mu mol h(-1), was obtained using such hierarchical nanostructured ZnIn2S4 under visible light irradiation. It is noteworthy that the H-2 evolution rate obtained is much higher compared to earlier reported photocatalysts. Considering the significance of morphologies for photocatalytic application, the formation mechanism has also been furnished. The unique hierarchical nanostructured ZnIn2S4 ternary semiconductor having hexagonal layer will have potential applications in solar cells, LEDs, charge storage, electrochemical recording, thermoelectricity and other prospective electronic and optical devices.

H2S is a corrosive, flammable and noxious gas, which can be neutralized by dissolving in alkaline media and employed as H2-source by utilizing inside semiconductor-assisted/photochemical reactors. Herein, through a facile hydrothermal route, a ternary nanostructured solid-solution of iron, zinc and sulfur was synthesized in the absence and presence of Ag-dopant, and applied as efficient photocatalyst of hydrogen fuel production from H2S media. The effect of pH on the photocatalyst performance was scrutinized and the maximum activity was attained at pH=11, where HS(-) concentration is high. BET, diffuse reflectance and photoluminescence studies indicated that the ternary solid-solution photocatalyst, in comparison to its solid-solvent (ZnS), has a greater surface area, stronger photon absorption and less charge recombination, which justify its superiority. Moreover, the effect of silver-dopant on the photocatalyst performance was examined. The investigations revealed that although silver could boost the absorption of photons and increase the surface area, it could not appreciably enhance the photocatalyst performance due to its weak influence on retarding the charge-recombination process. Finally, the phenomenon was discussed in detail from mechanistic viewpoint.

2S制氢性能进行了研究。结果表明: α, γ-MnS在可见光下都具有光解H₂S制氢活性, 且相比于热力学稳定相的α-MnS (4.24 μmol/(g·h)), 亚稳态的γ-MnS (23.38 μmol/(g·h))具有更好的催化性能。相对于可见光, α, γ-MnS在全光谱下的产氢速率明显提高, 其中γ-MnS在全光谱下具有最大的光解H₂S制氢活性, 其产氢速率可达 2272.69 μmol/(g·h)。值得注意的是, 在6 h的光催化测试过程中, α, γ-MnS都展示较好的抗光腐蚀能力和光催化稳定性。此外, 对α, γ-MnS光催化分解H₂S制氢机理进行了分析, 通过对α, γ-MnS光电化学性质的研究, 对其光催化活性存在差异的原因进行了探讨。]]>

Spin-polarized DFT+U computations have been performed to investigate the role of oxygen vacancies in dissociating H2S on the rutile TiO2(110) surface. A bridged O2c atom is demonstrated to be the most energetically favorable oxygen vacancy site, which makes V(O2c) an electron donator center and induces an isolated defect level with narrowed band gaps. A H2S molecule is adsorbed dissociatively over V(O2c), but molecularly on the perfect surface. For H2S dissociation, the HS/H intermediate state reveals the best thermal stability on both defected and perfect surfaces. Moreover, potential energy surface analysis shows that V(O2c) reduces markedly the energy barriers for the paths along H2S dissociation. This indicates oxygen vacancies to be efficient trap centers for H2S dissociation, as evidenced by a significant interfacial charge transfer promoted by vacancies. This work could provide insights into the role of oxygen vacancies in facilitating the decomposition of H2S on rutile TiO2(110) surface.