The decisive role of adsorbed OH^(*)in low‐potential CO electro‐oxidation on single‐atom catalytic sites

CO impurity-induced catalyst deactivation has long been one of the biggest challenges in proton-exchange membrane fuel cells,with the poisoning phenomenon mainly attributed to the overly strong adsorption on the catalytic site.Here,we present a mechanistic study that overturns this understanding by using Rh-based single-atom catalysis centers as model catalysts.We precisely modulated the chelation structure of the Rh catalyst by coordinating Rh with C or N atoms,and probed the reaction mechanism by surface-enhanced Raman spectroscopy.Direct spectroscopic evidence for intermediates indicates that the reactivity of adsorbed OH^(*),rather than the adsorption strength of CO^(*),dictates the CO electrocatalytic oxidation behavior.The RhN_(4)sites,which adsorb the OH^(*)intermediate more weakly than RhC4 sites,showed prominent CO oxidation activity that not only far exceeded the traditional Pt/C but also the RhC4 sites with similar CO adsorption strength.From this study,it is clear that a paradigm shift in future research should be considered to rationally design high-performance CO electro-oxidation reaction catalysts by sufficiently considering the water-related reaction intermediate during catalysis.

In situ investigation of atmospheric corrosion behavior of PCB-ENIG under adsorbed thin electrolyte layer

The effects of relative humidity (RH) on a printed circuit board finished with electroless nickel immersion gold (PCB-ENIG) under an adsorbed thin electrolyte layer (ATEL) were investigated in situ via the measurement of cathodic polarization curves, electrochemical impedance spectroscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy to clearly elaborate the corrosion behavior of PCB-ENIG in the atmospheric environment. Results indicated that the cathodic process of PCB-ENIG under ATEL was dominated by the reduction of dissolved oxygen, corrosion products, and H2O. The cathodic current density of PCB-ENIG increased progressively with increasing RH. Moreover, its cathodic current density in the solution was greater than that under ATEL. This result demonstrated that the diffusion process was not the controlling step during the limiting reduction of cathodic oxygen. When the polarization potentials were located in a more negative region, the cathodic polarization current density gradually decreased under 75% and 85% RH. Notably, the anodic process became the controlling step in the extremely thin liquid film during the remainder of the experiment.

Dielectric Relaxation of Adsorbed Water in Wood Cell Wall under Equilibrium and Non-Equilibrium State

This article summarized systematically the previous investigations on t he dielectric relaxation of wood, the main substances and extractives in wood at oven-dry state, and the dielectric relaxation based on the adsorbed water in w o od cell wall under equilibrium and non-equilibrium state. Moreover, some expect a tions for future research were proposed on this basis. The purpose of this artic le is to provide other researchers an overall understanding about the research i n this region, and further to promote the research onto a new and higher level.

Elastic Behaviors of Adsorbed Protein-like Chains

Elastic behaviors of protein-like chains are investigated by Pruned-Enriched-Rosenbluth method and modified orientation-dependent monomer-monomer interactions model. The protein-like chain is pulled away from the attractive surface slowly with elastic force acting on it. Strong adsorption interaction and no adsorption interaction are both considered. We calculate the characteristic ratio and shape factor of protein-like chains in the process of elongation. The conformation change of the protein-like chain is well depicted. The shape of chain changes from “rod” to “sphere” at the beginning of elongation. Then, the shape changes from “sphere” to “rod”. In the end, the shape becomes a “sphere” as the chain leaves away from the surface. In the meantime, we discuss average Helmoholtz free energy per bond, average energy per bond, average adsorbed energy per bond, average α-helical energy per bond, average β-sheet energy per bond and average contact energy per bond. On the other hand, elastic force is also studied. It is found that elastic force has a long plateau during the tensile elongation when there exists adsorption interaction. This result is consistent with SMFS experiment of general polymers. Energy contribution to elastic force and contact energy contribution to elastic force are both discussed. These investigations can provide some insights into the elastic behaviors of adsorbed protein chains.

Measurement and engineering application of adsorbed water content in fine-grained soils

In this paper,the content and density of adsorbed water in fine-grained soil are determined.According to the test results,the calculation method of compaction degree of the solid-phase and void ration of soil is improved.Four kinds of fine-grained soils from different regions in China were selected,and the adsorbed water content and density of four kinds of fine-grained soils were determined by thermogravimetry and volumetric flask method.Furthermore,SEM and XRD experiments were used to analyze the differences in the ability of each soil sample to absorb water.In order to study the compression characteristics of adsorbed water,four saturated soil samples were tested by consolidation method.The results show that the desorption temperature range of the adsorbed water and its density were equal to 100−115℃and 1.30 g/cm^(3),respectively.Adsorbed water plays a positive role in keeping the compressibility of fine-grained soil at a low rate when it has high water content.Besides,adsorbed water can be a stable parameter and is difficult to discharge during the operation period of subgrade.The settlement of fine-grained soil embankment is predicted by engineering example,and compared with the result of conventional calculation method.The results show that it is more close to the field monitoring results by using the improved void ratio of soil as the parameter.

The molecular conformation of silk fibroin regulates osteogenic cell behavior by modulating the stability of the adsorbed protein-material interface

Silk fibroin(SF)can be used to construct various stiff material interfaces to support bone formation.An essential preparatory step is to partially transform SF molecules from random coils toβ-sheets to render the material water insoluble.However,the influence of the SF conformation on osteogenic cell behavior at the material interface remains unknown.Herein,three stiff SF substrates were prepared by varying theβ-sheet content(high,medium,and low).The substrates had a comparable chemical composition,surface topography,and wettability.When adsorbed fibronectin was used as a model cellular adhesive protein,the stability of the adsorbed protein-material interface,in terms of the surface stability of the SF substrates and the accompanying fibronectin detachment resistance,increased with the increasingβ-sheet content of the SF substrates.Furthermore,(i)larger areas of cytoskeleton-associated focal adhesions,(ii)higher orders of cytoskeletal organization and(iii)more elongated cell spreading were observed for bone marrow-derived mesenchymal stromal cells(BMSCs)cultured on SF substrates with high vs.lowβ-sheet contents,along with enhanced nuclear translocation and activation of YAP/TAZ and RUNX2.Consequently,osteogenic differentiation of BMSCs was stimulated on highβ-sheet substrates.These results indicated that theβ-sheet content influences osteogenic differentiation of BMSCs on SF materials in vitro by modulating the stability of the adsorbed protein-material interface,which proceeds via protein-focal adhesion-cytoskeleton links and subsequent intracellular mechanotransduction.Our findings emphasize the role of the stability of the adsorbed protein-material interface in cellular mechanotransduction and the perception of stiff SF substrates with differentβ-sheet contents,which should not be overlooked when engineering stiff biomaterials.

Synthesis of Zeolite ZSM-35 in a Dry Powder System with an Adsorbed-State Template

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The Evolution of IR Spectra of H_2 Adsorbed on ZrO_2 with Changing Temperature（298－723K）

I.r.bands at 1559.0, 1441 .0, 1378 .9, 13603, 1031. 1,981 .4 and 947.3 cm -1 due tovarious types of dissociative adsorption of H2 over ZrO2 with changing temperatore wereobserved by in situ FT-IR spectroscopy.

SERS CHARACTERIZATION OF ADSORBED WATER AT VERY NEGATIVE POTENTIALS

Surface enhanced Raman scattering of water adsorbed at silver electrodes in very negative potential region was first observed and a simple model related to the adsorption configuration is proposed.

SURFACE-ENHANCED RAMAN SPECTRA OF p-AMINOBENZOIC ACID ADSORBED ON Ag2CO3 COLLOIDS

It was observed that the p-aminobenzoic acid(PABA)molecules adsorbed on A92CO3 colloids exhibited strong SERS effect,the enhancement factor is estimated at 10~7—10~8 The mechanism of SERS effect on PABA adsorbed on the colloids was discussed.

Local electric field and configuration of CO molecules adsorbed on a nanostructured surface with nanocones

Based on the nanostructured surface model that the （platinum, Pt） nanocones grow out symmetrically from a plane substrate, the local electric field near the conical nanoparticle surface is computed and discussed. On the basis of these results, the adsorbed CO molecules are modelled as dipoles, and three kinds of interactions, i.e. interactions between dipoles and local electric field, between dipoles and dipoles, as well as between dipoles and nanostructured substrate, are taken into account. The spatial configuration of CO molecules adsorbed on the nanocone surface is then given by Monte-Carlo simulation. Our results show that the CO molecules adsorbed on the nanocone surface cause local agglomeration under the action of an external electric field, and this agglomeration becomes more compact with decreasing conical angle, which results in a stronger interaction among molecules. These results serve as a basis for explaining abnormal phenomena such as the abnormal infrared effect （AIRE）, which was found when CO molecules were adsorbed on the nanostructured transition-metal surface.

AC IMPEDANCE OF PHENYL ISO-THIOCYANATE ADSORBED ON PT ELECTRODE

The paper presents ac impedance behaviours of phenyl iso-thiocyanate adsorbed on Pt electrode.Nyquist plots are analysed and simulated,and parameters of relative equivalent circuits are obtained.

Trimethylammonium Chlorochromate Adsorbed on Alumina:a New Reagent for the Oxidation of Alcohols to the Corresponding carbonyl Compounds

A new reagent. trimethylammonium chlorochromate adsorbed on alumina, suitable for the oxidation of hydroxy compounds to the corresponding carbonyl compounds is described.

Local field distribution and configuration of CO molecules adsorbed on the nanostructure platinum surface

This paper shows that the local electric field distribution near the nanostructure metallic surface is obtained by solving the Laplace equation, and furthermore, the configuration of CO molecules adsorbed on a Pt nanoparticle surface is obtained by using Monte Carlo simulation. It is found that the uneven local electric field distribution induced by the nanostructure surface can influence the configuration of carbon monoxide （CO） molecules by a force, which drags the adsorbates to the poles of the nanoparticles. This result, together with our results obtained before, may explain the experimental results that the nanostructure metallic surface can lead to abnormal phenomena such as anti-absorption infrared effects.

ANHARMONIC EFFECT ON ORIENTATIONAL ORDERING IN ADSORBED INCOMMENSURATE MONOLAYERS

The orientational ordering in adsorbed incommensurate monolayers is discussed in an anharmonic approach.A nonlinear relationship is predicted between the orientation of the monolayer relative to the substrate and the monolayer lattice parameter.Calculated values of the rninimum energy crientation angle for Ar on graphite are in good agreement with the experimental reported measurements.

SERS OF THE MOLECULES ADSORBED ON Cu SURFACE AT 4880Å EXCITATION

SERRS has been developed for observing a weak enhancement of SERS.A SERS from dye molecules 1555 adsorbed on Copper surface was observed at 4880Åexcitation and this result could be qualitatively explained by the antenna model of SERS.

ANALYSIS OF SYMMETRY OF C_60) ADSORBED ON THE SILVER MIRROR BY SERS SPECTRUM

The SERS spectrum of C_(60) was obtained by using silver mirror. From the SERS spectrum of C_(60) and the IR spectrum of C_(60), we proposed that C_(60) adsorbed on the silver mirror adopts a more ellipsoidal shape.

Promotion effect of adsorbed water/OH on the catalytic performance of Ag/activated carbon catalysts for CO preferential oxidation in excess H_2

Activated carbon （AC） supported silver catalysts were prepared by incipient wetness impregnation method and their catalytic performance for CO preferential oxidation （PROX） in excess H2 was evaluated. Ag/AC catalysts, after reduction in H2 at low temperatures （≤200 ℃） following heat treatment in He at 200 ℃ （He200H200）, exhibited the best catalytic properties. Temperature-programmed desorption （TPD）, X-ray diffraction （XRD） and temperature-programmed reduction （TPR） results indicated that silver oxides were produced during heat treatment in He at 200 ℃ which were reduced to metal silver nanoparticles in H2 at low temperatures （≤200 ℃）, simultaneously generating the adsorbed water/OH. CO conversion was enhanced 40% after water treatment following heat treatment in He at 600 ℃. These results imply that the metal silver nanoparticles are the active species and the adsorbed water/OH has noticeable promotion effects on CO oxidation. However, the promotion effect is still limited compared to gold catalysts under the similar conditions, which may be the reason of low selectivity to CO oxidation in PROX over silver catalysts. The reported Ag/AC-S-He catalyst after He200H200 treatment displayed similar PROX of CO reaction properties to Ag/SiO2. This means that Ag/AC catalyst is also an efficient low-temperature CO oxidation catalyst.

GEOMETRIC STRUCTURE OF ETHYLENOXIDE ADSORBED ON Cu(110) SURFACE

The binding energies of ethylene oxide (Et-O) adsorbed on Cu(110) surface for different adsorption sites and orientations are calculated with an atom superposition and electron delocalization molecular orbital (ASED-MO) using cluster models. It shows that the top site of Cu(110) surface is preferable for Et-O adsorption and the orientation of C-C bond of Et-O is parallel to the [110] direction of the substratc. The distance of an oxygen of Et-O to the Cu atom is approximately 1.5817(?). It is different from the supposition of C. Benndorf et al., in which the oxygen was proposed on the short bridge site with C-C bond orientating to [110] direction of Cu(110)

Abnormal IR Spectra of CO Adsorbed on the Surface of Glass Carbon Electrode Modified with Polypyrrole Film with Platinum Microparticles

Abnormal IR spectra of CO adsorbed at the surface of glass carbon electrode modified with polypyrrole film with Pt microparticles are reported.