Surface Chemistry and Catalysis of Rare Earth Oxides I．A Study of the Reactivity of Surface Hydroxyls on CeO_2 and Pr_6O_（11） by FT－IR Spectroscopy

The surface chemical properties of CeO2 and Pr6O11 have been investigated with FT-IR spectroscopy. The reactivities of surface hydroxyls were tested through the reaction of CO. Surface formate species are formed on CeO2 and Pr6O11 under CO atmosphere at 200℃ . and the reaction becomcs more prevailing at higher temperatures especially for partially reduced samples. The surface formate species are produced via the reaction of CO with surface hydroxyls which was confirmed by the reaction of CO with D2-treated CeO2 and Pr6O11. The Surface formate can be oxidized to carbonate at temperatures exceeding 300 ℃, and the surface hydroxyls could be recovered as the formate species decompose or are oxidized to carbonate species. The roles played by the surface hydroxyls and surface active sites in the CO oxidation are discussed.

Selective sulfur conversion with surface engineering of electrocatalysts in a lithium-sulfur battery

The sluggish kinetics of multiphase sulfur conversion with homogeneous and heterogeneous electrochemical processes,causing the“shuttle effect”of soluble polysulfide species(PSs),is the challenges in terms of lithium-sulfur batteries(LSBs).In this paper,a Mn_(3)O_(4-x) catalyst,which has much higher activity for heterogeneous reactions than for homogeneous reactions(namely,preferentialactivity catalysts),is designed by surface engineering with rational oxygen vacancies.Due to the rational design of the electronic structure,the Mn_(3)O_(4-x) catalyst prefers to accelerate the conversion of Li2S4 into Li_(2)S_(2)/Li_(2)S and optimize Li_(2)S deposition,reducing the accumulation of PSs and thus suppressing the“shuttle effect.”Both density functional theory calculations and in situ X-ray diffraction measurements are used to probe the catalytic mechanism and identify the reaction intermediates of MnS and Li_(y)Mn_(z)O_(4-x) for fundamental understanding.The cell with Mn_(3)O_(4-x) delivers an ultralow attenuation rate of 0.028% per cycle over 2000 cycles at 2.5 C.Even with sulfur loadings of 4.93 and 7.10mg cm^(-2) in a lean electrolyte(8.4μL mg s^(-1)),the cell still shows an initial areal capacity of 7.3mAh cm^(-2).This study may provide a new way to develop preferential-activity heterogeneous-reaction catalysts to suppress the“shuttle effect”of the soluble PSs generated during the redox process of LSBs.

Optimization of Photo-Fenton Catalyst Preparation Based Bamboo Carbon Fiber by Response Surface Methodology

In this paper,the residue from bamboo factory has been used to design photo-Fenton catalyst,which has the advantages of low cost and magnetic recycling.The photo-Fenton catalytic performance of the biocarbon-based catalyst was excellent and its optimal preparation process was also explored by response surface methodology.First,bamboo-carbon fiber was selected as the photo-Fenton catalyst carrier.Subsequently,the surface of the car-bon fiber was modified,with which dopamine,nano-Fe_(3)O_(4) and nano-TiO_(2) were successively loaded by hydro-thermal method.After the single factor tests,four factors including dopamine concentration,ferric chloride mass,P25 titanium dioxide mass and liquid-solid ratio were selected as the characteristic values.The degradation efficiency of photo-Fenton catalyst to methylene blue(MB)solution was treated as the response value.After the analysis of the response surface optimization,it was shown that the significance sequence of the selected 4 factors in terms of the MB degradation efficiency was arranged as follows:dopamine concentration>liquid-solid ratio>P25 titanium dioxide quality>ferric chloride quality.The optimal process parameters of fiber-carbon catalyst were affirmed as follows:the 1.7 mg/mL concentration of dopamine,the 1.2 g mass of ferric chloride,the 0.2 g mass of P25 titanium dioxide and the liquid-solid ratio of 170 mL/g.The experiment-measured average MB degra-dation efficiency performed by the optimized catalyst was 99.3%,which was nearly similar to the model-predicted value of 98.9%.It showed that the prediction model and response surface model were accurate and reliable.The results from response surface optimization could provide a good reference to design bamboo-based Fenton-like catalyst with excellent catalytic performance.

Recent advances on surface metal hydrides studied by solid-state nuclear magnetic resonance spectroscopy

Metal hydrides (MeH) on solid surfaces, i.e., surface MeH, are ubiquitous but criticalspecies in heterogeneous catalysis, and their intermediate roles have been proposed innumerous reactions such as (de)hydrogenation and alkanes activation, etc., however, thedetailed spectroscopic characterizations remain challenging. Solid-state nuclear magnetic resonance (ssNMR) spectroscopy has become a powerful tool in surface studies, asit provides access to local structural characterizations at atomic level from multipleviews, with comprehensive information on chemical bonding and spatial structures. Inthis review, we summarized and discussed the latest research developments on thesuccessful application of ssNMR to characterize surface MeH species on solid catalystsincluding supported single-site heterogeneous catalysts, bulk metal oxides and metalmodified zeolites. We also discussed the opportunities and challenges in this field, aswell as the potential application/development of state-of-the-art ssNMR technologies toenable further exploration of metal hydrides in heterogeneous catalysis.

Effects of Zr/Ti molar ratio in SO_4^(2-)/ZrO_(2-)TiO_2 calcined at different temperatures on its surface properties and glucose reactivity in near-critical methanol

Effects of Zr/Ti molar ratio in SO42-/ZrO2-TiO2 solid acid catalyst calcined at different temperatures on its surface properties and catalytic activity were thoroughly investigated in this paper. The physicochemical characteristics of prepared samples were determined by N2 adsorptiondesorption, XRD, NH3-TPD and XPS techniques, respectively. It was found that the crystallization temperature of the samples increased after the combination of ZrO2 and TiO2; and phase transformations from the anatase to the rutile of TiO2 species and the tetragonal to the monoclinic of ZrO2 species were effectively suppressed at higher temperature. The sample with a Zr/Ti molar ratio of 3/1 calcined at 450℃ showed the highest surface area and the most acid sites among all the tested samples. The acid site densities of samples were relatively closed to each other if they were calcined at the same temperature, however, decreased with the calcination temperature. The result indicates that the sulfur content in samples is a crucial factor to control the acid site density. Calcining the sample at 650℃ and higher temperatures resulted in a significant desorption of sulfate ion on the samples. The synthesized samples were evaluated as a potential catalyst for glucose conversion under the near-critical methanol conditions （200℃/4 MPa）. The results suggested that the relatively weaker acid sites of the catalyst were more favorable for the accumulation of methyl glucosides, while the moderate acid sites were responsible for the formation of methyl levulinate. The catalytic activity for methyl levulinate production almost increases linearly with the catalyst acid site density. The catalyst deactivation is due to the loss of sulfate ion and the two catalysts with Zr/Ti molar ratios of 3/1 and 1/3 could effectively alleviate the deactivation caused by sulfate solution in the reaction medium and can be reused after calcination with the reuse rate of over 90% in terms of the methyl levulinate selectivity.

Quantum Dots Compete at the Acme of MXene Family for the Optimal Catalysis

It is well known that two-dimensional(2D)MXene-derived quan-tum dots(MQDs)inherit the excellent physicochemical properties of the parental MXenes,as a Chinese proverb says,“Indigo blue is extracted from the indigo plant,but is bluer than the plant it comes from.”Therefore,0D QDs harvest larger surface-to-volume ratio,outstanding optical properties,and vigorous quantum confinement effect.Currently,MQDs trigger enormous research enthusiasm as an emerging star of functional materials applied to physics,chemistry,biology,energy conversion,and storage.Since the surface properties of small-sized MQDs include the type of surface functional groups,the functionalized surface directly determines their performance.As the Nobel Laureate Wolfgang Pauli says,“God made the bulk,but the surface was invented by the devil,”and it is just on the basis of the abundant surface functional groups,there is lots of space to be thereof excavated from MQDs.We are witnessing such excellence and even more promising to be expected.Nowadays,MQDs have been widely applied to catalysis,whereas the related reviews are rarely reported.Herein,we provide a state-of-the-art overview of MQDs in catalysis over the past five years,ranging from the origin and development of MQDs,synthetic routes of MQDs,and functionalized MQDs to advanced characterization techniques.To explore the diversity of catalytic application and perspectives of MQDs,our review will stimulate more efforts toward the synthesis of optimal MQDs and thereof designing high-performance MQDs-based catalysts.

Controllably tailoring external surface sites of nanosheet HZSM-5 for maximizing light olefins in catalytic cracking of n-decane

A series of triphenylethoxysilane(TPEOS)-modified nanosheet HZSM-5 catalysts(ZN-x,x=4%,8%and16%,mass)were synthesized by chemical liquid deposition to selectively change external acidity distributions.TPEOS modification was found to passivate some external Br?nsted and Lewis acid sites by37.8%,in which Br?nsted acid sites(BAS)were found more easily sacrificed by breaking the surface Al AO bond of bridging hydroxyl groups and forming Si AOASi bonds.The selectivity of ZN-8 catalyst for light olefins(ethylene,propylene and butene)in n-decane catalytic cracking is up to 26%(450℃,WHSV=10.95 h^(-1)),which is ca.78%higher than that of parent one.The better performance was attributed to the appropriate external acid density in ZN-8,which inhibits bimolecular hydrogen transfer reaction of light olefins on the adjacent acid sites,resulting in more olefins,few coke precursors and thus an excellent catalytic stability.

NH_3 Plasma Surface Treatments of Engineering Fluoropolymers: A Way to Enhance Adhesion of Ni or Cu Thin Films Deposited by Electroless Plating

This paper describes the electroless Ni or Cu plating of some fiuoropolymer substrates through a tin-free activation process. Materials subjected to surface metallization are commercial Teflon() FEP, Nafion(), ACLAR() and LaRCTM-CP1 thin films which have recently gained a large scientific and technological interest due to their excellent thermal, chemical, mechanical and dielectric properties. The original approach implemented in the present work involves: (i)the grafting of nitrogen-containing functionalities on the polymer surfaces through plasma treatments in ammonia, (ii) the direct catalysis of the so-modified surfaces via their immersion in a simple acidic PdCl2 solution (i.e. without using a prior surface sensitization in an acidic SnCl2 solution), and finally (iii) the electroless metallization itself. However, prior to the immersion in the industrial plating baths, the chemical reduction of the Pd+2 species (species covalently tethered on the nitrogen-containing groups) to metallic palladium (PdO) is shown to be a key factor in catalyzing the electroless deposition initiation. This is made by immersion in an hypophosphite (H2PO2-) solution. Wettability measurements and X-ray photoelectron spectroscopy (XPS) experiments are used to characterize every surface modification step of the developed process. A cross-hatch tape test was used to asses the adhesion strength of the electroless films that is shown qualitatively good. In addition, a fragmentation test was developed in combination with electrical measurements. Its use allows to distinguish different adhesion levels at the metal/polymer interface and to evidence the influence of some processing parameters.

The BOLS-NEP theory reconciling the attributes of undercoordinated adatoms,defects,surfaces and nanostructures

This article describes a theory unifying the unusual performance of the undercoordinated adatoms,point defects,terrace edges,surfaces,and nanostructures of various shapes.The ideas of bond order-length-strength correlation and the associated nonbonding electron polarization(BOLS-NEP)feature that bonds between undercoordinated atoms contract spontaneously.Bond contraction raises the local density of charge and energy.Bond strength gain deepens the interatomic potential well to trap the core and bonding electrons deeply.In turn,the locally and densely entrapped electrons polarize those partially occupying the valence band and above pertaining to the lower-coordinated atoms.The BOLS-NEP theory reconciles the unusual behaviors of undercoordinated systems and the size dependency of nanostructures in their lattice oscillating dynamics,mechanical strength,thermal stability,photon emissivity,chemical reactivity,dielectric permeability,associated with generation of polarized Dirac fermions,serving as carriers for extraordinary catalysis,hydrophobicity,fluidity,lubricity,as well as monolayer high-TC superconductivity and topological insulator conductivity.

Skyrmion-Like Solitons, Topological Quasi-Positroniums, and Soliton-Catalytic Effects in Graphite-Potassium Intercalation Compounds and Metal Surfaces

We have analyzed the narrow components in the positron annihilation angular correlation spectra of graphite-potassium intercalation with the theoretical formula, which is extended from “topological quasi-positronium” model and discusses the relation to the catalytic activity of hydrogens. One mechanism of the soliton-catalytic effect is proposed.

Novel synthesis of nickel oxide microsphere with high surface area and its catalytic application for carbon dioxide reforming of methane

Nickel oxide(NiO)microsphere with a large surface area was novelly synthesized through nickel bicarbonate(Ni(HCO3)2)precursor.The obtained nickel oxide(NiO)microsphere was characterized by X-ray pattern diffraction,scanning electron microscopy,CO2 temperature-programmed desorption,H2 temperature-programmed reduction,N2 adsorption/desorption and laser scattering particle size distribution analyzer.It was found that nickel oxide(NiO)synthesized by the thermal decomposition of Ni(HCO3)2through area hydrolysis,presented very nice microsphere with high surface area.The catalytic properties of obtained nickel oxide(NiO)microsphere were studied in the reaction of carbon dioxide reforming of methane where 91.3% conversion of CH4 with 93% conversion of CO2 was observed.Besides,the catalyst maintained high stability over 200 h on the stream.

Coherent Resonance for Rate Oscillations During CO Oxidation on Pt（110） Surfaces： Interplay Between Internal and External Noise

率摆动上的噪音的效果在磅(110 ) 表面上的公司氧化期间被调查，理论上并且数字地，由集中于内部噪音的相互影响(在里面) 由于在反应事件，和外部噪音的 stochasticity (在) 源于参数不安。表面被划分成被假定很好被混合的可变尺寸的房间，并且我们在一个单个房间内考虑行为。在噪音能导致随机的摆动的地方，注意对确定的 Hopf 分叉次于最低限度的参数区域被给予，哪个与噪音紧张的变化显示出最大值的 signal-to-noise 比率(SNR ) ，已知的同样协调的回声(CR ) 。由随机的正常理论，我们显示出那在并且在以到有效噪音的一条加权的添加剂路作出贡献导致 CR 以便 SNR 在 D-1/ 飞机显示出山脉形状 D 和 1/measures 力量在并且在分别地。它被看那为在太大(在) ， CR 行为与在(在里面) 不再存在。数字模拟与理论结果显示出好协议。

Surface Coordination Decouples Hydrogenation Catalysis on Supported Metal Catalysts

Supported metal catalysts integrating advantages of catalytic hydrogenation and stoichiometric reduction are highly desirable for the green production of fine chemicals.Decoupling catalytic hydrogenation into H_(2)activation and selective reduction taking place at different locations is expected to provide an effective strategy to fabricate such catalyst systems.Herein,we report a decoupled hydrogenation system by modifying Pt catalysts supported on reducible In2O3 with ethylenediamine(EDA).The system exhibits good catalytic performance in oximes production from nitroalkanes,an industrially important reaction,by employing H_(2).Systematic studies demonstrate that the surface coordination of EDA on Pt is crucial to passivate the Pt surface from nitro hydrogenation without inhibiting H_(2)activation.The activated H_(2)species can then transfer and reduce the In_(2)O_(3)support in situ to generate sustainable stoichiometric reducing agents for the chemoselective reduction of nitroalkanes.Based upon the mechanistic understanding,a sustainable strategy for the production of oximes has been successfully fabricated.

Surface Engineered Ru_(2)Ni Multilayer Nanosheets for Hydrogen Oxidation Catalysis

The hydrogen oxidation reaction(HOR)in alkaline conditions is of great importance for the application of anion exchange membrane fuel cells(AEMFCs).However,the electrocatalysts for alkaline HOR generally suffer from the disadvantage of sluggish kinetics.Herein,we have fabricated Ru2Ni multilayered nanosheets(Ru2Ni MLNSs)in the layer-by-layer manner and engineered the surface properties via postannealing for efficient alkaline HOR.Detailed investigations reveal that such annealing at different temperatures can alter the surface properties of Ru2Ni MLNSs and thus regulate their adsorption abilities toward*H and*OH.In particular,the optimal catalyst exhibits a mass activity of 4.34 A mgRu−1 at an overpotential of 50 mV,which is 18.1 and 13.2 times higher than those of Ru/C(0.24 A mgRu−1)and Pt/C(0.33 A mgPt−1),respectively.Theoretical calculations indicate that the presence of surface O atoms can facilitate the HOR activity while the excessive coverage of O atoms on Ru2Ni surface leads to the strengthened H binding and the decay of HOR activity.This work not only provides an efficient catalyst for alkaline HOR,but it also may shed new light on the design of high-performance catalysts for electrocatalysis and beyond.We have fabricated Ru2Ni multilayer nanosheets(Ru2Ni MLNSs)and realized the surface engineering via an annealing process.Detailed investigations show that such surface engineering can regulate the surface properties and thus promote the alkaline HOR activity.Consequently,the optimal catalyst exhibits a much higher activity than those of commercial Ru/C and Pt/C and is a promising catalyst for alkaline HOR.

压力影响硅基防热材料界面多相催化的微观机理研究

反应分子动力学模拟是阐明高温壁面效应微观致热机理、深化高速飞行器非平衡气动热认知的重要途径之一,然而通过人为增加压力实现计算效率提升的微观模拟,往往会导致反应路径和速率系数差异,进而影响气动热,造成机理认知偏差。采用基于ReaxFF力场的分子动力学方法,以离解氧原子在硅基防热材料表面的催化复合反应体系为对象,计算分析了不同气相压力条件下的基元反应速率、表面覆盖率和复合系数,用于获得基元反应速率常数与压力的量化关系,明确通过增压提高计算效率的上限范围。结果表明,增压可导致主导反应路径从吸附相间作用至气相-吸附相作用的转变,且使基元反应速率常数-压力的关系偏离实验/飞行条件下的规律。在1200 K条件下、单原子碰撞的压力范围内,各基元反应步骤的速率常数均随压力的降低而下降。其中,ER1~ER3复合反应的速率常数随压力呈近似线性变化,速率常数分别与压力的1.10179、1.01686和0.91654次方呈线性关系;LH1~LH3复合反应的速率常数与压力呈对数关系,且对数前因子显著小于非单原子碰撞区;热解附反应的速率常数与压力呈指数关系。根据气相压力影响催化反应机制的微观机理,以基元反应速率常数-压力关系可以稳定解析为判据,提出了人为增加压力的约束上限条件:以体系高度为特征长度的努森数应大于102量级,以保证气固单原子碰撞。相关研究为气固界面反应的分子模拟方法和防热材料微观催化数据的累积提供了支撑。

Surface/Interface Engineering of Hierarchical MoO_(2)/MoNi_(4)@Ru/RuO_(2)Heterogeneous Nanosheet Arrays for Alkaline Water Electrolysis with Fast Kinetics

Realizing the hydrogen economy by water electrolysis is an attractive approach for hydrogen production,while the efficient and stable bifunctional catalysts under high current densities are the bottleneck that limits the half-cell reactions of water splitting.Here,we propose an approach of hydrothermal and thermal annealing methods for robust MoO_(2)/MoNi_(4)@Ru/RuO_(2) heterogeneous cuboid array electrocatalyst with multiplying surface-active sites by depositing a monolayer amount of Ru.Benefiting from abundant MoO_(2)/MoNi_(4)@Ru/RuO_(2)heterointerfaces,MoO_(2)/MoNi_(4)@Ru/RuO_(2) heterogeneous cuboid array electrocatalysts effectively drive the alkaline water splitting with superior hydrogen evolution reaction(HER)and oxygen evolution reaction(OER)performances.The synthesized MoO_(2)/MoNi_(4)@Ru/RuO_(2) has high HER activity,which realizes the working overpotentials of 48 mV at 50 mA·cm^(-2),further achieving overpotentials of 230 mv for industry-level 1000 mA·cm^(-2) in alkaline water electrolysis.Moreover,it also showed an enhanced OER activity than commercial RuO_(2) with a small overpotential of 280 mV at 200 mA·cm^(-2) in alkaline media.When building an electrolyzer with electrodes of(-)MoO_(2)/MoNi_(4)@Ru/RuO_(2)IIMo02/MoNig@Ru/RuO_(2)(+),a cell voltage of 1.63 V and 1.75 V is just required to support the current density of 200 mA·cm^(-2) and 500 mA-cm^(-2) in alkaline water electrolysis,much lower than that of the electrolyzer of(-)Pt/CIIRuO_(2)(+).This work demonstrates that MoO_(2)/MoNig@Ru/RuO_(2) heterogeneous nanosheet arrays are promising candidates for industrial water electrolysis applications,providing a possibility for the exploration of water electrolysis with a large currentdensity.

响应面法优化光电脱色降解直接橙

结合单因素试验与响应面法,对直接橙染料的光电脱色工艺进行了系统优化.探讨了TiO2浓度、NaCl浓度、外加电压、光照时间等多个因素对脱色效果的影响.试验结果表明,在优化的工艺条件下,即TiO2质量浓度为0.15 g/L、NaCl质量浓度为2.85 g/L时,对直接橙溶液(pH 7.0)施加7.60 V电压电解,辅以250 W的高压汞灯(主峰波长365 nm)进行照射,仅需20 min,直接橙的脱色率即可达到98.81%.

pH Dependent plasmon-driven surface-catalysis reactions of p,p'-dimercaptoazobenzene produced from para-aminothiophenol and 4-nitrobenzenethiol

In this paper,we studied the pH dependent plasmon-driven surface-catalysis(PDSC) reactions of p,p'-dimercaptoazobenzene(DMAB) produced from para-aminothiophenol(PATP) and 4-nitrobenzenethiol(4NBT) both theoretically and experimentally.The surface enhanced Raman spectrum(SERS) of DMAB produced from PATP and 4NBT on Ag films in solutions with various pH values has been measured.The simulation and experimental results indicated that the pH dependence of PATP appeared in acidic environment and came from the amino group NH2.Furthermore,the ratio of intensity of Raman peak caused by PATP and DMAB indicated that this acidic sensor had higher pH sensitivity when it was excited by photons of higher energy.

本科物理化学实验中开展计算化学教学初探

计算化学已成为研究化学过程的重要辅助手段,因此在大学本科物理化学实验课程教学阶段引入计算化学实验内容的需求也越来越迫切。根据复旦大学化学系本科生教学的实际情况,我们设计了一个纯理论计算的物理化学实验《H2在Cu表面解离反应动力学模拟》,并成功在4届本科生中开展了此项实验。在本论文中,我们详细介绍了理论实验设计的思路以及具体开展实验的细节。根据开展实验过程中的结果,我们总结了教学实验效果,并探讨了一些普遍存在的问题,如学生关于计算化学必须使用的Linux操作系统熟练度不够,对计算化学背后的知识点掌握不牢固等问题。针对这些问题,我们探讨了未来在课程设置上可能的改进方案以及后续实验课程的设计思路。总之,我们在物理化学实验课程中成功开展了计算化学实验内容,取得了良好的效果,证明了该方面教学改革的可行性。

TiO_(2)-Ag纳米复合材料的制备及其光电催化性能研究

载流子在等离激元金属纳米粒子上的快速复合,导致传统的光电催化剂效率显著降低,通过金属和半导体的复合可实现热电子和空穴的分离以提升光电催化效率。采用Ag纳米粒子与半导体TiO_(2)纳米粒子复合提高其光电催化活性,并探索了催化活性提升的机理,研究了TiO_(2)-Ag纳米复合材料之间空间电荷区能带弯曲以及内置电场的作用,为设计高性能SPR光电催化剂提供理论和实验依据。以对氨基苯硫酚(PATP)及对硝基苯硫酚(PNTP)的光电催化偶联反应为探针,研究了TiO_(2)-Ag纳米复合材料的催化性能。结果表明TiO_(2)的引入提高了Ag的SPR催化活性,其主要原因是TiO_(2)的引入可提高TiO_(2)-Ag间电子和空穴的分离效率。