Photocatalytic production of hydrogen from H2S solutions over CdS/Pt colloids

CdS/Pt colloids sensitize the photodecomposition of H₂S into H₂ and S in aqueous solutions under visible light irradiation. The dependence of H₂ evolution on the amounts of CdS, Pt, [S^2–] and pH has been studied.

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CdS H₂S H₂ S . H₂ CdS, Pt, [S^2–] pH .

     

Pd修饰对Cd0.8Zn0.2S/SiO2光催化甘油水溶液制氢性能的影响

用等体积浸渍法制备了不同Pd负载量的Pd/Cd_0.8Zn_0.2S/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Cd_0.8Zn_0.2S固溶体,金属Pd负载未对固溶体Cd_0.8Zn_0.2S/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,Cd_0.8Zn_0.2S/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/Cd_0.8Zn_0.2S/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。     

Growth and spectroscopic characterization of CdSe nanoparticles synthesized from CdCl2 and Na2SeSO3 in aqueous gelatine solutions

CdSe nanoparticles were synthesized in comparatively mild conditions from Na₂SeSO₃ and CdCl₂ in aqueous gelatine solutions. Kinetics of the formation and growth of CdSe nanocrystals as well as the effect of various parameters of reacting mixture on the size of CdSe nanocrystals are investigated. Optical properties of thin gelatine films, containing CdSe nanoparticles of different size, are characterized using absorption and Raman spectroscopy.     

Inhibition of positronium formation in aqueous solutions of mixed solutes: NO3 in Cd and in allylamine solutions

The ability of NO₃⁻ to inhibit positronium formation in the presence of Cd²⁺ and of allylamine in aqueous solutions is investigated and found to be the same as in plain NO₃⁻ solutions. The results are discussed on the basis of the spur model, with emphasis on the mechanisms at the origin of the limited inhibition. It is suggested that, in water, limited inhibition would arise from the selectivity of the solute to react with particles in different solvation states.     

Influence of the substituent on selective photocatalytic oxidation of aromatic compounds in aqueous TiO2 suspensions

Experimental results are reported showing that the photocatalytic oxidation of aromatic compounds containing an electron-donor group (EDG) gives rise mainly to ortho- and para-monohydroxy derivatives while in the presence of an electron-withdrawing group (EWG) all the monohydroxy derivatives are obtained.     

Experimental evidence for the hydrogen evolution site in photocatalytic process on Pt/TiO2

A hydrogen-deuterium isotope effect on the title reaction is observed. The separation factor of the reaction is found to be 5.3 ± 0.5, which is similar to the separation factor reported on Pt electrode, but different from that observed on TiO₂ electrode. The Pt sites are assigned to the reduction site on the catalyst.     

Photocatalytic hydrogen evolution from aqueous Pt/TiO2 suspension in the presence of oxalic acid

Accumulation of titanium (III) oxalate was found to accompany hydrogen evolution upon UV irradiation of aqueous suspensions containing Pt/TiO₂ and oxalic acid. The former appears to take part in the process of hydrogen evolution as an electron relay.     

The effect of CTAB on Na2SO4 nucleation in mixed Na2SO4/CTAB aerosols by FTIR-ATR technology

FTIR-ATR technology is used to study the efflorescence kinetic of Na_2SO_4 and mixed Na_2SO_4/CTAB aerosols.As the RH decreased linearly,the v_3-SO_4~2 band shifts from 1094 cm~1 to 1132 cm~1,suggesting the phase transition of Na_2SO_4 from solution to crystal phase(Ⅲ).For pure Na_2SO_4 aerosols,the ERH is 75.1%RH,whereas the efflorescence point of mixed Na_2SO_4/CTAB aerosols(74.2%) is lower.By further analysis of IR differential spectra,the ratio of Na_2SO_4 crystals in mixed aerosols is only 62.7%and the heterogeneous nucleation rate of Na_2SO_4 in Na_2SO_4/CTAB mixed aerosols is lower than that in pure Na_2SO_4 aerosols.They showed that CTAB assembled into reversed micelle and part Na_2SO_4 droplets are in the core to form core-shell structure,and CTAB shell prevents core Na_2SO_4 solutions from crystallizing.However,the counter ion Br for CTAB reversed micelle can interact with Na~+ ions,which decreases the crystallization rate of free Na_2SO_4 droplets and ERH is delayed.     

Mechanism of alkyl iodide reduction to alkanes in aqueous solutions of Na2PtCl4?NaI?HClO4

Platinum(II) catalyzes the reduction of alkyl iodides to alkanes according to a mechanism involving oxidative addition of RI to Pt(II), reduction of the product complex RPt(IV) to RPt(II) by iodide ions and protolysis of the latter particle.

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(II) , RI Pt^II, - RPt^IV RPt^II .

     

Influence of cobalt precursors on the catalytic activity of the cobalt oxide/Al2O3 catalysts

Cobalt acetate and cobalt nitrate were employed as precursors to prepare different kinds of Co₃O₄/Al₂O₃ catalysts. The catalysts were used to decompose VOC's such as xylene, isopropyl alcohol and butyl acetate. This revised version was published online in June 2006 with corrections to the Cover Date.     

AgGaS2-type photocatalysts for hydrogen production under visible light: Effects of post-synthetic H2S treatment

Bulky AgGaS₂ was synthesized as a p-type semiconductor photocatalyst by a conventional solid state reaction under N₂ flow for hydrogen production under visible light. To remove impurity phases involved in the synthesized material and improve crystallinity, the material was treated at various temperatures of 873-1123 K under H₂S flow. Impurity phases were identified as β-Ga₂O₃ and Ag₉GaS₆ with the cell refinements of XRD and the local coordination structure around gallium atom in AgGaS₂ was investigated by EXAFS. As the H₂S-treatment temperature increased, the contribution from impurity phases was diminished. When the temperature reached 1123 K, the impurity phases were completely removed and the material showed the highest photocatalytic activity. Thus, the post-synthetic H₂S treatment could be applied for the synthesis of sulfide-type photocatalysts with high activity.     

NaOH浓度对Na0.44MnO2储钠性能的影响

我们通过球磨法及后续的高温焙烧合成出了短棒状的Na_0.44MnO₂,并研究了其作为碱性水溶液钠离子电池正极时,电解液NaOH浓度对其电化学性能的影响。结果表明,提高NaOH浓度有利于抑制嵌氢反应的发生并改善电极的循环性能和倍率性能,但同时也会造成析氧反应的提前触发,浓度过高时则又会降低其倍率性能。Na_0.44MnO₂在8 mol·L^?1 NaOH中表现出了最佳的电化学性能,0.5C(1C=121 mA·g^?1)的电流密度下,比容量达到79.2 mAh·g^?1,50C时,仍能释放出35.3 mAh·g^?1的比容量,在0.2–1.2 V(vs.NHE)的电压窗口内,500周后容量保持率64.3%。此外,我们也发现缩小电压窗口可以减少副反应、改善循环性能。Na_0.44MnO₂在浓碱电解液中也表现出了优异的耐过充能力。上述结果不仅表明通过优化电解液体系和测试条件可大大改善Na_0.44MnO₂的储钠性能,同时也证实了Na_0.44MnO₂作为一种水溶液钠离子电池正极材料,在大规模储能领域具有良好的应用前景。     

Adsorption of formaldehyde and butynediol from aqueous solutions on a Cu2C2-silica gel catalyst

The effect of equilibrium concentration on adsorption has been studied at different temperatures and the nature of isotherms is discussed. For the formaldehyde-Cu₂C₂-silica gel system, Freundlich type equations describe the data satisfactorily.

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. . -Cu₂C₂- .

     

Effect of methylviologen on the hydrogen evolution at mercury electrodes in aqueous buffer solutions

Methylviologen reduces the hydrogen overvoltage and gives a catalytic hydrogen wave at the dropping mercury electrode in aqueous buffer solutions (pH 3–7). The electrochemical behaviour of the catalytic hydrogen evolution was studied by dc and pulse polarography, potential-step chronoamperometry, and constant potential electrolysis. A possible reaction scheme has been proposed to explain the experimental results, in which the reduced neutral form of methylviologen MV⁰ is assumed to be oxidized to a monocation radical MV^·+ by the weak acid component in the buffer solution. Generation of MV^·+ during the hydrogen evolution is supported by the visual observation of a blue colour appearing at the surface and also in the vicinity of the electrode when a large catalytic current is flowing in dc polarography and constant potential electrolysis.     

Preparation of SiO2-Pt-CdS composite photocatalyst and its photocatalytic activity for hydrogen evolution under visible light

CdS nanoparticles were prepared by the precipitation method. Pt was loaded on CdS by photodeposition. SiO₂-Pt-CdS was synthesized via hydrolysis of tetraethylorthosilicate in the presence of Pt-CdS. The samples were characterized by XRD, BET, PL and UV-Vis techniques. The photocatalytic activity of the samples for hydrogen evolution was investigated under visible light irradiation (λ ≥ 420 nm). The stability and activity of CdS was improved by coating SiO₂.     

Polyphenylsulfone/multiwalled carbon nanotubes mixed ultrafiltration membranes: Fabrication,characterization and removal of heavy metals Pb2+, Hg2+, and Cd2+ from aqueous solutions

Polyphenylsulfone/multiwalled carbon nanotubes/polyvinylpyrrolidone/1-methyl-2-pyrrolidone mixed matrix ultrafiltration flat-sheet membranes were fabricated via phase inversion process to inspect the heavy metals separation efficacy from aqueous media. Fabricated membranes cross-sectional morphological changes and the topographical alterations were assessed with Scanning electron microscopy (SEM) and atomic force microscopy (AFM). Particularly, MWCNTs assisted membranes exhibited better permeability ability as well as heavy metal removal enactment than virgin membrane. The dead-end filter unit was engaged in current research to examine the permeability and heavy metal removal competence of membranes. With the continuous enhancement of MWCNTs wt% in a polymer matrix, significant enhancement was observed with pure water flux study, from 41.69 L/m² h to >185 L/m² h as well as with the heavy metals separation study. Added additive MWCNTs can impact the pore sizes in membranes. The heavy metal separation results achieved, the membrane with 0.3 wt% of MWCNTs (PCNT-3) exhibited >98%, >76% and >72% for Pb²⁺, Hg²⁺ and Cd²⁺ ions, respectively. Overall, MWCNTs introduced PPSU membranes exposed best outcomes with heavy metals contained wastewater treatment.     

Interaction of Na2B12H11SH with liposomes: Influence on zeta potential and particle size

The interaction of Na₂B₁₂H₁₁SH (BSH) with liposomes has been studied. BSH is a compound used clinically in boron neutron capture therapy of glioblastoma, and is known to enter tumor cells. Liposomes were used as a model for studying the interaction of BSH with cell membranes. BSH led to changes in the zeta potential of liposomes consisting of DODAB (dioctadecyldimethylammonium bromide) alone or with DOPC (dioleylphosphatidylcholine) or DOPE (dioleylphosphatidylethanolamine). It also led to changes of the size of DODAB liposomes, with a maximum size at small zeta potentials. A firm binding of BSH with the head groups of the lipid must be assumed.     

Metal powder addition effect on the photocatalytic reactions and the photo-generated electric charge collected at an inert electrode in aqueous TiO2 suspensions

The photocatalytic reaction in an aqueous TiO₂ suspension has been found to be enhanced by the additiona of some metal powders such as copper, silver, nickel and cobalt into the suspension. Just mixing a metal powder into the suspension gave nearly the same efficiency as metal-loading on the semiconductor particles. The effect is attributed to the rapid transfer of the photogenerated electrons from the TiO₂ to the metal particles, resulting in the effective separation of the electrons and holes.

The photo-current measurements were performed using inert collecting electrodes in the suspensions of TiO₂, where formate was added as a hole scavenger, with and without a metal powder. Higher anodic photocurrent was obtained in the presence of a metal than in its absence, indicating that the metal-mediated electron transfer reaction occurs more effectively from the electron-rich TiO₂ particles to the collecting electrode than the direct discharge of the electron-rich TiO₂ on the collecting electrode.