化学链燃烧技术中非金属载氧体的研究进展

简述化学链燃烧技术是一种能实现CO_2内分离、提高燃烧效率的燃烧技术及钙基载氧体具有更高的氧传递能力、价格低廉、环境友好的特性,介绍非金属载氧体CaSO_4不同实验测试与表征手段的研究现状,分析认为串行流化床非常适合于非金属载氧体CaSO_4化学链燃烧技术的应用,并提出未来的研究方向。

Recent developments in copper-based, non-noble metal electrocatalysts for the oxygen reduction reaction

The high cost of Pt-based catalysts and the sluggish dynamics of the oxygen reduction reaction （ORR） severely hinder the rapid development of fuel cells, Therefore, the search for inexpensive, non-noble metal catalysts to substitute Pt-based catalysts has become a critical issue in the ORR research field, As an earth-abundant element, the use of Cu to catalyze the ORR has been explored with the ultimate target of finding a replacement for Pt-based catalysts in fuel cells. This review mainly focuses on recent research progress with Cu-based ORR catalysts and aims to aid readers＇ understanding of the status of development in this field. The review begins with a general update on the state of knowledge pertaining to ORR, This is followed by an overview of recent research based on Cu nanomaterial catalysts, which comprises Cu complexes, compounds, and other structures. Charting the development of Cu-based ORR catalysts shows that designing Cu-based materials to mimic active enzymes is an effective approach for ORR catalysis. By collecting recent developments in the field, we hope that this review will promote further development of Cu-based ORR catalysts and their application in fuel cells.

Co_3O_4 nanoparticles assembled on polypyrrole/graphene oxide for electrochemical reduction of oxygen in alkaline media

The development of highly efficient catalysts for cathodes remains an important objective of fuel cell research. Here, we report Co3O4 nanoparticles assembled on a polypyrrole/graphene oxide electrocatalyst （Co3O4/Ppy/GO） as an efficient catalyst for the oxygen reduction reaction （ORR） in alkaline media. The catalyst was prepared via the hydrothermal reaction of Co2＋ ions with Ppy-modified GO. The GO, Ppy/GO, and Co3O4/Ppy/GO were characterized using scanning electron microscopy, Fourier-transform infrared spectroscopy, and X-ray photoelectron spectroscopy. The incorporation of Ppy into GO nanosheets resulted in the formation of a nitrogen-modified GO po-rous structure, which acted as an efficient electron-transport network for the ORR. With further anchoring of Co3O4 on Ppy/GO, the as-prepared Co3O4/Ppy/GO exhibited excellent ORR activity and followed a four-electron route mechanism for the ORR in alkaline solution. An onset potential of -0.10 V vs. a saturated calomel electrode and a diffusion limiting current density of 2.30 mA/cm^2 were achieved for the Co3O4/Ppy/GO catalyst heated at 800 ℃; these values are comparable to those for noble-metal-based Pt/C catalysts. Our work demonstrates that Co3O4/Ppy/GO is highly active for the ORR. Notably, the Ppy coupling effects between Co3O4 and GO provide a new route for the preparation of efficient non-precious electrocatalysts with hierarchical porous structures for fuel cell applications.

Preparation of Nitrogen-Doped Carbon Catalyst to Oxygen Reduction Reaction and Influence of Protective Gas Flowing on Its Activity

A non-precious metal catalyst MnHMTA/C to oxygen reduction reaction was prepared by py- rolyzing a precursor from manganese chloride, hexamethylenetetramine and acetylene black in nitrogen gas atmosphere. The effect of heat treatment temperature and flowing of nitrogen gas were investigated. A catalyst with the highest activity can be obtained at 700 ℃. Mn（Ⅱ） ion was changed to MnO in heat treatment, which improved the catalytic activity of the catalyst. Hexamethylenetetramine takes part in the formation of active site of the catalyst as its decomposed gases. The flowing of protective gas takes the decomposed gases out of the tube furnace and brings negative effect on the catalytic activity of the MnHMTA/C catalyst.

Iron-glutamate-silicotungstate ternary complex as highly active heterogeneous Fenton-like catalyst for 4-chlorophenol degradation

A novel iron-glutamate-silicotungstate ternary complex（FeШGluS iW） was synthesized from ferric chloride（FeI II）,glutamic acid（Glu）,and silicotungstic acid（SiW）,and used as a heterogeneous Fenton-like catalyst for 4-chlorophenol（4-CP） degradation at neutral pH value. The prepared FeШGluS iW was characterized using inductively coupled plasma atomic emission spectroscopy,thermogravimetry,Fourier-transform infrared spectroscopy,ultraviolet-visible diffuse reflectance spectroscopy,X-ray diffraction,and field-emission scanning electron microscopy. The results showed that FeШGluS iW has the formula [Fe（C5H8NO4）（H2O）]2SiW 12O40？13H2O,with glutamate moiety and Keggin-structured SiW 12O404- heteropolyanion. The catalyst showed high catalytic activity in 4-CP degradation in the dark and under irradiation. Under the conditions of 4-CP 100 mg/L,FeШGluS iW 1.0 g/L,H2O2 20 mmol/L,and pH = 6.5,4-CP was completely decomposed in 40 min in the dark and in 15 min under irradiation. When the reaction time was prolonged to 2 h,the corresponding total organic carbon removals under dark and irradiated conditions were ca. 27% and 72%,respectively. The high catalytic activity of FeI IIGluS iW is resulted from hydrogen bonding of H2O2 on the FeI IIGluS iW surface. The enhanced degradation of 4-CP under irradiation arises from simultaneous oxidation of 4-CP through Fenton-like and photocatalytic processes respectively catalyzed by ferric iron and the SiW 12O404- hetropolyanion in FeШGluS iW.

A high performance non-noble metal electrocatalyst for the oxygen reduction reaction derived from a metal organic framework

The development of a non-precious metal electrocatalyst （NPME） with a performance superior to commercial Pt/C for the oxygen reduction reaction （ORR） is important for the commercialization of fuel cells. We report the synthesis of a NPME by heat-treating Co-based metal organic frameworks （ZIF-67） with a small average size of 44 nm. The electrocatalyst pyrolyzed at 600 ~C showed the best performance and the performance was enhanced when it was supported on BP 2000. The resulting electrocatalyst was composed of 10 nm Co nanoparticles coated by 3-12 layers of N doped graphite layers which as a whole was embedded in a carbon matrix. The ORR performance of the electrocatalyst was tested by rotating disk electrode tests in O2-saturated 0.1 mol/L KOH under ambient conditions. The electrocatalyst （1.0 mg/cm~] showed an onset potential of 1.017 V （[vs. RHE] and a half-wave potential of 0.857 V （vs. RHE], which showed it was as good as the commer- cial Pt/C （20 BgPt/cm2）. Furthermore, the electrocatalyst possessed much better stability and re- sistance to methanol crossover than Pt/C.

Ordered macroporous boron phosphate crystals as metal-free catalysts for the oxidative dehydrogenation of propane

Ordered macroporous materials with rapid mass transport and enhanced active site accessibility are essential for achieving improved catalytic activity.In this study,boron phosphate crystals with a three-dimensionally interconnected ordered macroporous structure and a robust framework were fabricated and used as stable and selective catalysts in the oxidative dehydrogenation(ODH)of propane.Due to the improved mass diffusion and higher number of exposed active sites in the ordered macroporous structure,the catalyst exhibited a remarkable olefin productivity of^16 golefin gcat^-1 h^-1,which is up to 2–100 times higher than that of ODH catalysts reported to date.The selectivity for olefins was 91.5%(propene:82.5%,ethene:9.0%)at 515℃,with a propane conversion of 14.3%.At the same time,the selectivity for the unwanted deep-oxidized CO2 product remained less than 1.0%.The tri-coordinated surface boron species were identified as the active catalytic sites for the ODH of propane.This study provides a route for preparing a new type of metal-free catalyst with stable structure against oxidation and remarkable catalytic activity,which may represent a potential candidate to promote the industrialization of the ODH process.

Structural sensitivity of heterogeneous catalysts for sustainable chemical synthesis of gluconic acid from glucose

Gluconic acid and its derivatives have been widely used in the food and pharmaceutical industries. Conventional processes that involve the conversion of glucose into gluconic acid via fermentation present several technological shortcomings as they involve energy-intensive wastewater treatment and complex enzyme separation. Greener oxidation processes over heterogeneous metal catalysts have attracted increasing attention worldwide. Au-, Pt-and Pd-based heterogeneous catalysts have been extensively used for the chemical oxidation of glucose to gluconic acid. Bimetallic catalysts synthesized by adding either noble or inexpensive metals have also presented excellent performance for the oxidations of glucose. In particular, particle size, which has been recognized as the most important factor that affect catalytic performances, could be rationally tuned by changing the types of support and ligand as well as the synthesis conditions. In this perspective review, we summarize and critically discuss the recent advances in the structural design of mono-and bimetallic catalysts for the oxidation of glucose in aqueous media. Furthermore, the challenges of developing catalysts for the green synthesis of gluconic acid have been highlighted. This review provides alternative insights for designing effective catalytic materials for the catalytic oxidation of bio-derived oxygenates over heterogeneous catalysts.

High activity and durability of carbon-supported core-shell PtPx@Pt/C catalyst for oxygen reduction reaction

Alloying Pt with transition metals can significantly improve the catalytic properties for the oxygen reduction reaction(ORR).However,the application of Pt-transition metal alloys in fuel cells is largely limited by poor long-term durability because transition metals can easily leach.In this study,we developed a nonmetallic doping approach and prepared a P-doped Pt catalyst with excellent durability for the ORR.Carbon-supported core-shell nanoparticles with a P-doped Pt core and Pt shell(denoted as PtPx@Pt/C)were synthesized via heat-treatment phosphorization of commercial Pt/C,followed by acid etching.Compositional analysis using electron energy loss spectroscopy and X-ray photoelectron spectroscopy clearly demonstrated that Pt was enriched in the near-surface region(approximately 1 nm)of the carbon-supported core-shell nanoparticles.Owning to P doping,the ORR specific activity and mass activity of the PtP_(1.4)@Pt/C catalyst were as high as 0.62 mA cm^(–2)and 0.31 mAμgPt–^(1),respectively,at 0.90 V,and they were enhanced by 2.8 and 2.1 times,respectively,in comparison with the Pt/C catalyst.More importantly,PtP_(1.4)@Pt/C exhibited superior stability with negligible mass activity loss(6%after 30000 potential cycles and 25%after 90000 potential cycles),while Pt/C lost 46%mass activity after 30000 potential cycles.The high ORR activity and durability were mainly attributed to the core-shell nanostructure,the electronic structure effect,and the resistance of Pt nanoparticles against aggregation,which originated from the enhanced ability of the PtP_(1.4)@Pt to anchor to the carbon support.This study provides a new approach for constructing nonmetal-doped Pt-based catalysts with excellent activity and durability for the ORR.

Fe,N,S-doped porous carbon as oxygen reduction reaction catalyst in acidic medium with high activity and durability synthesized using CaCl_2 as template

Proton exchange membrane fuel cells suffer from the sluggish kinetics of the oxygen reduction reaction(ORR)and the high cost of Pt catalysts.In the present work,a high‐performance ORR catalystbased on Fe,N,S‐doped porous carbon(FeNS‐PC)was synthesized using melamine formaldehyderesin as C and N precursors,Fe(SCN)3as Fe and S precursors,and CaCl2as a template via a two‐stepheat treatment without a harsh template removal step.The results show that the catalyst treated at900℃(FeNS‐PC‐900)had a high surface area of775m2/g,a high mass activity of10.2A/g in anacidic medium,and excellent durability;the half‐wave potential decreased by only20mV after10000potential cycles.The FeNS‐PC‐900catalyst was used as the cathode in a proton exchangemembrane fuel cell and delivered a peak power density of0.49W/cm2.FeNS‐PC‐900therefore hasgood potential for use in practical applications.

Earth-abundant amorphous catalysts for electrolysis of water

The generation of hydrogen through the electrolysis of water has attracted attention as a promising way to produce and store energy using renewable energy sources.In this process,a catalyst is very important to achieve a high‐energy conversion efficiency for the electrolysis of water.A good catalyst for water electrolysis should exhibit high catalytic activity,good stability,low cost and good scalability.Much research has been devoted to developing efficient catalysts for both the hydrogen evolution reaction(HER)and oxygen evolution reaction(OER).Traditionally,it has been accepted that a material with high crystallinity is important to serve as a good catalyst for HER and/or OER.Recently,catalysts for HER and/or OER in the electrolysis of water splitting based on amorphous materials have received much interest in the scientific community owing to the abundant unsaturated active sites on the amorphous surface,which form catalytic centers for the reaction of the electrolysis of water.We summarize the recent advances of amorphous catalysts for HER,OER and overall water splitting by electrolysis and the related fundamental chemical reactions involved in the electrolysis of water.The current challenges confronting the electrolysis of water and the development of more efficient amorphous catalysts are also discussed.

Induced growth of Fe-N_x active sites using carbon templates

Highly active Fe-N_x sites that effectively improve the performance of non-precious metal electrocatalysts for oxygen reduction reactions（ORRs） are desirable. Herein, we propose a strategy for introducing a carbon template into a melamine/Fe-salt mixture to inductively generate highly active Fe-N_x sites for ORR. Using 57 Fe M？sbauer spectroscopy, X-ray photoelectron spectroscopy, and X-ray diffraction, we studied the structural composition of the Fe and N co-doped carbon catalysts.Interestingly, the results showed that this system not only converted inactive Fe and Fe-carbides into active Fe-N_4 and other Fe-nitrides, but also improved their intrinsic activities.

Influence of GdCl_3 addition on purifying effectiveness and properties of Mg-10Gd-3Y-0.5Zr alloy

In order to improve the purifying efficiency of RJ6 flux,5%(mass fraction) GdCl3 was introduced into the flux for refining Mg-10Gd-3Y-0.5Zr(GW103K) alloy.The results show that the RJ6 flux containing 5%GdCl3 exhibits better adsorption ability to nonmetallic inclusions than the one without GdCl3.Moreover,the mechanical,corrosion properties and fluidity of the alloy refined with RJ6 flux and RJ6 flux containing 5%GdCl3 were investigated,respectively.It is found that these properties are improved to a certain degree due to the removal of nonmetallic inclusions in the alloy.Thermodynamic analysis and surface tension experiments indicate that the main reason can be ascribed to the decrease of the surface tension of the flux with 5%GdCl3,which promotes the combination of flux and nonmetallic inclusions.

Recent development of supported monometallic gold as heterogeneous catalyst for selective liquid phase hydrogenation reactions

The great potential of gold catalysts for chemical conversions in both industrial and environmental concerns has attracted increasing interest in many fields of research.Gold nanoparticles supported by metal oxides with high surface area have been recognized as highly efficient and effective green heterogeneous catalyst even at room temperature under normal reaction conditions,in gas and liquid phase reactions.In the present review,we discuss the recent development of heterogeneous,supported monometallic gold catalysts for organic transformations emphasizing mainly liquid phase hydrogenation reactions.Discussions on the catalytic synthesis procedures and the promoting effect of other noble metals are omitted since they are already worked out.Applications of heterogeneous,supported monometallic catalysts for chemoselective hydrogenations in liquid phase are studied including potential articles during the period 2000–2013.

Influence of Nonionic Surfactant Addition on Drag Reduction of Water Based Nanofluid in a Small Diameter Pipe

The goal of this research was to determine the impact of nonionic surfactants on drag reduction effect in water and metal oxide nanofluid. Two nonionic surfactants （Rokacet 07 and Rokanol KT） and copper（II） oxide wa- ter-based nanofluid were examined. Friction factors in a 4 mm diameter pipe for the Reynolds number between 8000 and 50000 were determined. Results showed that addition of nonionic surfactants caused the decrease of fric- tion factor in water and nanofluid. The drag reduction effect was similar in both cases. Presence of nanoparticles in the system has no great influence on drag reduction effect.

Research progress of polyoxometalates in catalytic oxidation

Polyoxometalates(POMs),as a class of multinuclear clusters,are polymerized of oxygen and early high-valent transition metals(e.g.,Mo,W,V and Nb).Based on the geometry of heteroatoms and the ratio of heteroatoms to coordination atoms,POMs can be classified into six classical configurations including Keggin-type,Dawson-type,Anderson-type,Waugh-type,Silverton-type,and Lindqvist-type.They exhibit the diverse structures and versatile properties,which enrich their applications in catalysis,medicine,electrochemistry,magnetism,and so on.The chemistry of POMs is an important branch of inorganic chemistry with a history of more than 200 years.It intersects with physical chemistry,analytical chemistry,structural chemistry,biochemistry,environmental chemistry,material chemistry and many other fields.Modern chemistry of POMs has developed from single POMs synthesis to controllable molecular design synthesis,from simple POMs monomer to high-dimensional,high-core and other novel structure clusters constructed with POMs as building units.Especially,POMs are considered as electron stores due to their strong ability to bear and release electrons,indicating they have redox properties.Therefore,POMs have received increasing attentions as redox heterogeneous catalysts.To resolve the problem of the high solubility of POMs,the design synthesis and performance research of functional complexes with POMs as inorganic ligands or non-coordination templates have become one of hot spots.The encapsulation of POMs into the crystalline architecture results in multifunctional hybrid materials,which combine the merits of POMs and the organic frameworks to achieve specific properties.With the increase of consciousness for environmental protection,green oxidants such as hydrogen peroxide and oxygen are utilized as main oxidants for the oxidation.The combination of POMs-based materials with environment friendly oxidants can efficiently catalyze various oxidation reactions,such as epoxidation of olefin,oxidation of sulfurcontaining compounds,oxidation of alcohols,oxidation of alkanes and so on.In this paper,an overview of recent advances of POMs in catalytic oxidation was presented.

“酸碱盐”复习之“一到十”教学实践

酸碱盐知识是初中化学的重点和难点,纵观几年全国中考试题,酸碱盐的化学性质及应用都被列为考查重点。这部分知识具有很大的灵活性和深度,学生掌握起来有相当的难度,很多学生遇到酸碱盐的习题会感觉无从下手、茫然无措。其实,初中酸碱盐的知识虽然庞杂,但也有规律可循,只要我们在复习中多总结、类比,学生学起来自然就会容易很多。以下是笔者结合自己的教学实践,总结出学习酸碱盐知识要注意的"一到十"。

Encapsulated FeP nanoparticles with in-situ formed P-doped graphene layers:Boosting activity in oxygen reduction reaction

Nonprecious metal-based oxygen reduction reaction(ORR)electrocatalysts with high efficiency in both alkaline and acidic media are being intensively studied for the purpose of replacing expensive Pt-based catalysts;however,it is still a challenge to achieve superior ORR performances,especially in acidic media.Herein,by pyrolysis of mixed precursors of diammonium phosphate,melamine and hemin,we prepared a nanocomposite catalyst(denoted as FeP@PGL)composed of nitrogen-doped carbon nanosheets with embedded FeP nanoparticles(NPs),which were encapsulated by in-situ formed phosphorus-doped graphene layers.It is found that phosphorous was preferentially doped in the coating layers on FeP NPs,instead of in the carbon nanosheets.The FeP@PGL catalyst exhibited excellent ORR performance,with the onset and half-wave potential up to 1.01 and 0.90 V vs.the reversible hydrogen electrode(RHE)in alkaline media,and0.95 and 0.81 V vs.RHE in acidic media,respectively.By thorough microscopy and spectroscopy characterizations,the interfacial charge transfer between the encapsulated FeP NPs and P-doped graphene layers was identified,and the local work function of the catalyst surface was also reduced by the interfacial interaction.The interfacial synergy between the encapsulated FeP and phosphorus-doped graphene layers was essential to enhance the ORR performance.This study not only demonstrates the promising ORR properties of the encapsulated-FeP-based nanocomposite catalyst,but also provides direct evidence of the interfacial charge transfer effect and its role in ORR process.

Early stages of non-classic crystal growth

Investigation of early stages of crystal growth revealed that crystal growth in some systems may not follow the classic route.In the early stages of inorganic crystal growth,precursor molecules and/or nanocrystallites may aggregate into large and disordered particles with the assistance of some polymers or biomolecules.Surface crystallization of these aggregates would then take place to form shells with high crystallinity and density,followed by an extension of the crystallization from surface to core.This so-called reversed crystal growth mechanism has been found in crystallization of several inorganic compounds including zeolites,perovskites,metals and metal oxides,and will be identified in more material systems.The establishment of this new crystal growth route gave us more freedom to control the morphology of crystals and to understand the formation mechanism of many natural minerals.This article gives a brief review of the recent research in this field by featuring some typical examples of the reversed crystal growth.

Acid promoted Ni/NiO monolithic electrode for overall water splitting in alkaline medium

Exploring and designing bi-functional catalysts with earth-abundant elements that can work well for both hydrogen evolution reaction（HER） and oxygen evolution reaction（OER） in alkaline medium are of significance for producing clean fuel to relieve energy and environment crisis.Here,a novel Ni/NiO monolithic electrode was developed by a facile and cost-effective acid promoted activation of Ni foam.After the treatment,this obtained monolithic electrode with a layer of NiO on its surface demonstrates rough and sheet-like morphology,which not only possesses larger accessible surface area but also provides more reactive active sites. Compared with powder catalysts,this monolithic electrode can achieve intimate contact between the electrocatalyst and the current collector,which will alleviate the problem of pulverization and enable the stable function of the electrode. It can be served as an efficient bi-functional electrocatalyst with an overpotential of 160 mV for HER and 290 mV for OER to produce current densities of 10 mA cm^（-2） in the alkaline medium. And it maintains benign stability after 5,000 cycles,which rivals many recent reported noble-metal free catalysts in 1.0mol L^（-1） KOH solution. Attributed to the easy,scalable methodology and high catalytic efficiency,this work not only offers a promising monolithic catalyst but also inspires us to exploit other inexpensive,highly efficient and self-standing noble metalfree electrocatalysts for scale-up electrochemical water-splitting technology.