大学化学中的案例教学——以氢氧化合反应为例

大学化学课程信息量大、知识点多，面广，而且学时数有限，在教学过程中引入“案例教学法”，将课本上很多的知识点通过一个典型例子有机地联系起来，从而取得良好的教学效果。该文以氢氧化合反应为倒，将化学热力学、化学动力学，氧化还原反应、电化学，清洁能源氢燃料电池以及其在军事中的应用等知识点有机联系起来，对大学化学的课堂教学将起到事半功倍之效。

Carbon supported IrM(M= Fe,Ni,Co) alloy nanoparticles for the catalysis of hydrogen oxidation in acidic and alkaline medium

We studied the alloying effect in lr-based alloys on the catalysis of the hydrogen oxidation reaction （HOP,） in both acidic and alkaline medium. IrFe, lrNi and IrCo alloy catalysts with nanoparticle size of 〈S nm were obtained by our solvent-vaporization plus hydrogen reduction method. The second metal played an important role in tuning the crystal structure and surface electronic structure of the Ir-based alloy catalyst. Among the lrFe, IrCo and lrNi alloy catalysts, Ni induced a mid-sized contrac- tion of the lr lattice, and gave the best HOR activity in both acidic and alkaline medium. In acidic medium, the weakening of the Ir-Had interaction caused by the electronic effect of M （M = Fe, Ni, Co） alloying is responsible for the enhancement of HOR activity. The oxophilic effect of the catalytic metal surface, which affects OHad adsorption and desorption and surface Had coverage, has a large impact on the HOR activity in the case of alkaline medium,

Prospect of vapor phase catalytic H2O2 production by oxidation of water

Vapor phase catalytic hydrogen peroxide production by oxidation of water is possible by coupling the reaction with oxidation of an organic sacrificial reductant. It is potentially a safer process than direct synthesis from H2 and O2. Based on mechanistic information available mostly for liquid phase catalytic processes, feasible reaction mechanisms for such coupled reactions are proposed based on which desirable catalyst properties are identified. It is found that the surface-adsorbed oxygen bond is an important parameter for identifying desirable catalysts. Thermodynamics can be used to identify the types of organic oxidation reactions that can couple with water oxidation such that H2O2 formation becomes thermodynamically favorable. Reactions such as epoxidation of alkenes and selective oxidation of alkanes to alcohols cannot provide sufficient thermodynamic driving force, whereas oxidation of alcohols to aldehydes and to acids can. Finally, further research is suggested to identify catalytic properties important for H2O2 decomposition and for coupling selective oxidation of organic compounds to oxidation of H2O in order to facilitate development of H2O2 production coupled with selective organic oxidation.

Leaching of cuprite through NH_4OH in basic systems

Cuprite is a difficult oxide to leach under acidic conditions(for the maximum extraction of50%).In this research,the feasibility of leaching cuprite in an ammoniacal medium was studied.The working conditions addressed here were the liquid/solid ratio(120:1-400:1mL/g),stirring speed(0-950r/min),temperature(10-45℃)and NH4OH concentration(0.05-0.15mol/L).In addition,different ammoniacal reagents(NH4F and(NH4)2SO4)were analyzed.The experiments were performed in a2L reactor with a heating mantle and a condenser.The most important results were that the maximum leaching rate was obtained at pH10.5,0.10mol/L NH4OH,45℃,4h,850r/min and a liquid/solid ratio of400:1,reaching a copper extraction rate of82%.This result was related to the non-precipitation of copper in solution by the formation of copper tetra-amine (Cu(NH2)4^2+).The liquid/solid ratio and stirring speed were essential for increasing the cuprite leaching.The maximum leaching rate was achieved at higher temperatures;however,significant copper leaching rate occurred at temperatures near the freezing point of water(17.9%over4h).Increasing NH4OH concentration and decreasing particle size increased the cuprite leaching rate.The two ammoniacal reagents(NH4F and(NH4)2SO4)had low extraction rate of copper compared with NH4OH.The kinetic model representing cuprite leaching was a chemical reaction on the surface.The order of the reaction with respect to the NH4OH concentration was1.8,and it was inversely proportional to the radius of the ore particles.The calculated activation energy was44.36kJ/mol in the temperature range of10-45℃.

Linear-regioselective hydromethoxycarbonylation of styrene using Ru-clusters/CeO2 catalyst

Hydroalkoxycarbonylation of olefins has been considered to be one of the most attractive methods to synthesize esters. Controlling the regioselectivities of linear esters(L) and branched esters(B) is a challenging project for researchers working in this reaction. Although most of the attention has been paid to control the regioselectivity through ligand design in homogeneous catalytic systems, study in the area is still limited. Herein, Ru-clusters/CeO2 is employed as a heterogeneous catalyst for the hydromethoxycarbonylation of styrene without any additives. After optimization of the reaction conditions, the conversion of styrene is > 99% with 83% and 12% regioselectivity of linear and branched ester, respectively. By using different supports(CeO2(nanoparticle), CeO2-rod, and CeO2-cube), three catalysts including Ru-clusters/CeO2, Ru/CeO2-rod, and Ru/CeO2-cube are prepared and applied in the reaction. Structural characterizations demonstrate that the L/B ratio is related to the Ru size of supported Ru catalysts. Further Raman characterization and NH3-TPD demonstrate that the metal-support interaction and the concentration of oxygen vacancy of the catalyst have a great influence on the Ru size. The mechanism and kinetic analysis for this reaction are also investigated in this work.

Synthesis of TS-1 Films on Porous Supports for Epoxidation ofAllyl Chloride by Hydrogen Peroxide

Titanium silicalite-1(TS-1)films were synthesized on stainless steel plate,glass slide and monolith supports via an in-situ hydrothermal method.Characterization data showed that the formation of TS-1 films was easier on the porous flat support with rough surface such as monolith than on the smooth non-porous supports like glass slide and stainless steel plate.The film on the monolith had the highest uniformity and smallest size of crystals.The catalytic property of monolithsupported film was tested for epoxidation of allyl chloride(ACH)by H2O2in a fixed bed reactor.Under the condition of a methanol(solvent)/ACH(90% )/H2O2(30% )ratio of 12:1:1,a LHSV of 1.35 h-1and a temperature of 318 K,the conversion of allyl chloride and the selectivity to epichlorohydrin reached 79% and 51% ,respectively.

Direct carbon dioxide hydrogenation to produce bulk chemicals and liquid fuels via heterogeneous catalysis

The hydrogenation of carbon dioxide(CO_(2))to produce chemicals and transportation liquid fuels in huge demand via heterogeneous thermochemical catalysis achieved using renewable energy has received increasing attention,and substantial advances have been made in this research field in recent years.In this study,we summarize our progress in the rational design and construction of highly efficient catalysts for CO_(2) hydrogenation to methanol,lower olefins,aromatics,and gasolineand jet fuel-range hydrocarbons.The structure‐performance relationship,nature of the active sites,and mechanism of the reactions occurring over these catalysts are explored by combining computational and experimental evidence.The results of this study will promote further fundamental studies and industrial applications of heterogeneous catalysts for CO_(2) hydrogenation to produce bulk chemicals and liquid fuels.

Nano Fibrous Cerium（IV） Hydrogen Phosphate Membrane Self Supported Indole Polymerization Agent

Nanosized fibrous cerium（IV） hydrogen phosphate membrane, Ce（HPO4）2·2.9H20 （nCePf）, was prepared and characterized by chemical, XRD （X-ray diffraction）, TGA （thermogravimetric analysis）, SEM （scanning electron microscopy） and TEM （transmission electron microscopy）. Novel supported nanofibrous Ce（IV） phosphate/polyiondole nanocomposite membranes were prepared via in-situ chemical oxidation of the monomer that was promoted by the reduction of Ce（IV） ions present in the inorganic matrix. The presence of Ce（IV） ions allows redox reactions necessary to oxidative polymerization to occur. The resultant material was characterized by TGA, elemental （C, H, N） analysis and FT-IR （Fourier transform spectroscopy）. SEM images of the resulting nanocomposite reveals a uniform distribution of the polymer on the inorganic matrix. Amount of polyindole polymer present in the composite is found to be - 7.0%.

Study on Preparation of Porous ZnO Microspheres and Photocatalytic Performance

This paper introduces the method of porous ZnO microspheres by sodium citrate assisted hydrothermal synthesis with a mild, economy： first, basic synthesis globose precursor of Zinc Carbonate Hydroxide, then followed by thermal decompose the precursor to obtain porous Zinc Oxide microspheres. The morphology and structure of the precursor and synthesized porous microspheres were characterize by a series of methods, and did a series of experiments by changing dosage and reaction time of the sodium citrate and urea, finally the paper discussed the formation mechanism of porous ZnO microspheres.

Application of hierarchically porous metal-organic frameworks in heterogeneous catalysis:A review

Hierarchically porous metal-organic frameworks(H-MOFs)with micro-,meso-and macropores have emerged as a popular class of crystalline porous materials that have attracted extensive interests,and they have been studied in diverse applications,especially in heterogeneous catalysis.The hierarchical structures enable sufficient diffusion and accessibility to the active sites of the molecules and permit the encapsulation of catalytic guest molecules to exploit more possibilities with enhanced catalytic performance.In this review,we have summarized the recent representative developments of H-MOFs in the field of heterogeneous catalysis,which includes oxidation reaction,hydrogenation reaction,and condensation reaction.Emphasis is placed on the multiple functions of hierarchical structures,and the catalytic activity,selectivity,stability,recyclability,etc.of the industrial utility of H-MOFs.Finally,the prospects and challenges of H-MOFs in heterogeneous catalysis and the remaining issues in this field are presented.

Bifunctional catalysts of Co3O4@GCN tubular nanostructured （TNS） hybrids for oxygen and hydrogen evolution reactions

Catalysts for oxygen and hydrogen evolution reactions （OER/HER） are at the heart of renewable green energy sources such as water splitting. Although incredible efforts have been made to develop efficient catalysts for OER and HER, great challenges still remain in the development of bifunctional catalysts. Here, we report a novel hybrid of Co3O4 embedded in tubular nanostructures of graphitic carbon nitride （GCN） and synthesized through a facile, large-scale chemical method at low temperature. Strong synergistic effects between Co3O4 and GCN resulted in excellent performance as a bifunctional catalyst for OER and HER. The high surface area, unique tubular nanostructure, and composition of the hybrid made all redox sites easily available for catalysis and provided faster ionic and electronic conduction. The Co3O4@GCN tubular nanostructured （TNS） hybrid exhibited the lowest overpotential （0.12 V） and excellent current density （147 mA/cm^2） in OER, better than benchmarks IrO2 and RuO2, and with superior durability in alkaline media. Furthermore, the Co3O4@GCN TNS hybrid demonstrated excellent performance in HER, with a much lower onset and overpotential, and a stable current density. It is expected that the Co3O4@GCN TNS hybrid developed in this study will be an attractive alternative to noble metals catalysts in large scale water splitting and fuel cells.

Green synthesis of NiFe LDH/Ni foam at room temperature for highly efficient electrocatalytic oxygen evolution reaction

Clean energy technologies such as water splitting and fuel cells have been intensively pursued in the last decade for their free pollution. However, there is plenty of fossil energy consumed in the preparation of the catalysts,which results in a heavy pollution. Therefore, it is much desired but challenging to fabricate high-efficiency catalysts without extra energy input. Herein, we used a facile one-pot room-temperature method to synthesize a highly efficient electrocatalyst of nickel iron layered double hydroxide grown on Ni foam(NiFe LDH/NF) for oxygen evolution reaction(OER). The formation of the NiFe LDH follows a dissolutionprecipitation process, in which the acid conditions by hydrolysis of Fe^3+ combined with NO3^- could etch the NF to form Ni^2+. Then, the obtained Ni^2+ was co-precipitated with the hydrolysed Fe^3+ to in situ generate NiFe LDH on the NF. The NiFe LDH/NF exhibits excellent OER performance with a low potential of about 1.411 V vs. reversible hydrogen electrode(RHE) at a current density of 10 m A cm^-2, a small Tafel slope of 42.3 mV dec^-1 and a significantly low potential of ~1.452 V vs. RHE at 100 mA cm^-2 in 1 mol L^-1 KOH. Moreover, the material also keeps its original morphology and structure over 20 h. This energy-efficient strategy to synthesize NiFe LDH is highly promising for widespread application in OER catalyst industry.

Syntheses of amides via iodine-catalyzed multiple sp3 C-H bonds oxidation of methylarenes and sequential coupling with N,N-dialkylformamides

The oxidative coupling of methylarenes and N,N-dialkylformamides was developed, and the appropriate reaction conditions were established. By using I2 as the catalyst, and tert-butyl hydroperoxide(TBHP) as the oxidant, the reaction provided N,N-dialkylamides or N-alkylamides with moderate yields via multiple sp3 C-H bonds activation of methylarenes in aqueous and metal-free conditions.

Platinum nanowires catalyzed direct amidation of aldehydes and amines

Different from the conventional synthesis methods and substrates, we designed a brand new method for synthesizing amides with platinum nanowires as catalysts and tert-butylhydroperoxide(TBHP) as the oxidant. Influence of factors, such as the catalyst, solvents, and the reaction temperature, were studied to determine the optimal reaction conditions. In addition, we explored the substrate generality and observed excellent yields.