HREELS study on coadsorption of oxygen and cyclohexanone on the Pt(111) surface

The coadsorption of cyclohexanone and oxygen on Pt(111) has been investigated by HREELS and TDS. At 205 K the presence of oxygen induces an "extra" red\|shift of the C--O stretching of coadsorbed cyclohexanone. Heating this coadsorbed surface from 205 to 250 K leads to further dehydrogenation to form intermediate species and to complete disappearance of the C--O stretching band. Above 300 K, the molecule rings of dehydrogenation species cleave to form hydrocarbon fragments and CO molecules which directly desorb into the vacuum or react with preadsorbed oxygen to produce CO\-2 which leave the surface immediately. TDS results provide further evidence that the preadsorbed oxygen promotes the decomposition of cyclohexanone.

Adsorption of Gold on Iridium

The work described in this paper is a study of gold adsorption on the whole tip surface of iridium field emitter. The study has been carried out using field emission microscope. Changes in electron work function of the iridium substrate which are produced by vapor of deposition of submonolayers of gold in ultra high vacuum have been measured by noting the changes in the slope of Fowler-Nordheim plots. The same procedure for studying the adsorption of copper on iridium?[1] was followed to study the adsorption of gold on iridium. Adsorption of gold was examined on the iridium surface containing the (100) ring which could not be removed thermally.

Adsorption of glycine at the anatase TiO_(2)/water interface: Effects of Ca^(2+) ions

Adsorption reactions of amino acids(AAs)on TiO_(2) nanoparticles(NPs)play an important role in the available nutrients in soils and sediments.The pH effects on glycine adsorption have been studied,but little is known about its coadsorption with Ca^(2+)at the molecular level.Combined attenuated total reflectance Fourier transform infrared(ATR-FTIR)flow-cell measurements and density functional theory(DFT)calculationswere used to determine the surface complex and corresponding dynamic adsorption/desorption processes.The structures of glycine adsorbed onto TiO_(2) were closely associated with its dissolved species in the solution phase.The presence of Ca^(2+)exerted different influences on glycine adsorption within pH 4−11,thus affecting its migration rate in soils and sediments.The mononuclear bidentate complex at pH 4−7,involving the COO−moiety of zwitterionic glycine,remained unchanged in the absence and presence of Ca^(2+).At pH 11,the mononuclear bidentate complex with deprotonated NH2 can be removed from the TiO_(2) surface upon coadsorption with Ca^(2+).The bonding strength of glycine on TiO_(2) was much weaker than that of the Ca-bridged ternary surface complexation.Glycine adsorption was inhibited at pH 4 but was enhanced at pH 7 and 11.

Shape-dependence in seeded-growth of Pd-Cu solid solution from Pd nanostructure towards methanol oxidation electrocatalyst

Ultrathin Pd nanosheets(NSs)have great advantages in catalysis due to their large specific surface area and high percentage of under-coordinated atoms.However,the electrochemical performance still can be improved via composition-controllable growth of their solid solution.Herein,seeded alloying strategy was proposed to synthesize Pd-Cu solid solution from Pd NSs and Pd-Cu nanostructures with tunable molar ratios obtained by changing the amount of Cu precursor.As compared to the pristine Pd NSs,the Pd-Cu solid solution shows significantly enhanced methanol oxidation reaction(MOR)performance over those of Pd NSs and homemade Pd/C as the incorporation of Cu weakens the adsorption of CO intermediate on Pd in the MOR process.The choice of template is pivotal to the growth,as a shape-dependent behavior could be identified in the alloying of Cu with Pd nanosheets enclosed by{111}and{100}facets,Pd nanocubes enclosed by{100}facet,and Pd nano-tetrahedrons enclosed by{111}facet.The Pd-Cu solid solution with tunable composition can only be obtained from Pd NSs and the shape-dependent alloying process is mainly determined by the diffusion barrier and the minimum diffusion depth of the different facets.

FeOOH上掺入Ni和Cu引起的羟基和含氮中间物的共吸附行为实现加速氨氧化反应中的脱氢过程

氨是一种很有前途的能源载体,由于其高氢含量和无碳的特点,可用于燃料电池,并可作为电解水制氢装置中水的替代氧化底物.然而,人们对氨电氧化反应(AOR)的机理认识不足,且缺乏廉价、高效的AOR催化剂,因而阻碍了氨基能源系统的发展.在这项工作中,我们通过光诱导化学沉淀法合成的新型Ni和Cu共掺杂的多孔FeOOH纳米棒(NiCu-FeOOH)可以作为AOR催化剂,其具有高效的催化活性(阳极电流密度达到10 mA cm^(-2)时执行电压为1.41 V)和在氨碱溶液中优异的稳定性.实验数据和理论计算结果表明,异质的Ni和Cu原子的协同作用使得NiCu-FeOOH表面的Ni和Fe位点表现出更合适的电子结构,他们可以共同吸附含氮中间产物和羟基,并使其吸附自由能位于火山形曲线的顶部,从而加速AOR脱氢.决速步骤的后移(*NH_(2)+*OH形成步骤移至*N_(2)H_(3)+*OH形成步骤)和决速步骤较低的能垒(0.86 eV)揭示了Ni和Cu的共掺策略使FeOOH晶体对催化AOR更具活性.本文创新地提出了涉及含氮中间物和羟基的共吸附反应途径,以更好地描述和模拟AOR过程,这为设计低成本和稳定的AOR催化剂开辟了新的路径.

Synergistic co-removal of zinc(Ⅱ) and cefazolin by a Fe/amine-modified chitosan composite

A novel Fe/amine modified chitosan composite(Fe/N-CS) was facilely synthesized and showed higher affinity to both Zn(Ⅱ) and cefazolin(CEF) than its precursors.Synergistic co-adsorption of them by Fe/NCS was observed in varied conditions.The adsorption amount maximally increased by 100.1% for Zn and68.2% for CEF in bi-solute systems.The initial adsorption rate of Zn(Ⅱ) also improved with CEF.The increasing temperature facilitated coadsorption.The results of the preloading tests,FTIR/XPS characterizations and DFT calculations suggested that(1) both polyamines and Fe sites participated in the adsorption of Zn(Ⅱ) and CEF,(2) Zn(Ⅱ) could serve as a new efficient site for CEF,forming [amineZn-CEF]/[FeOH-Zn-CEF] ternary complexes,and(3) the co-presence of CEF shielded the electrostatic repulsion between protonated amines and Zn(Ⅱ),contributing to the enhancement of Zn(Ⅱ) adsorption.Further,the ion strength exerted positive and negative influences on the adsorption of Zn(Ⅱ) and CEF,respectively.Additionally,CEF and Zn(Ⅱ) were successively recovered by 0.1 mol/L NaOH followed by2 mmol/L HCl.Fe/N-CS could be stably reused five times.The findings imply that Fe/N-CS is promising for the highly efficient co-removal of concurrent heavy metals and antibiotics.

Structure and properties of Ni(110) surface coadsorbing chlorine and oxygen

The coadsorption of chlorine with oxygen on Ni(110) surface has been investigated by XPS, UPS, AES and work function measurements. The chlorine preadsorption drastically inhibits the further uptake of oxygen. On the contrary, precovered oxygen has hardly any influence on the additional adsorption of chlorine due to the incorporation of precovered oxygen into the subsurface driven by the chlorine coadsorption. ARXPS measurements provide the evidence for this coadsorption model. The thermal desorption of chlorine and oxygen from the coadsorption surface is very similar to that of both individual adsorbates under the same heating conditions, but the desorption temperature of both the adsorbates apparently decreases on the coadsorption surface. The coadsorption and thermodesorption mechanisms are also discussed in detail.