“Buckets effect”in the kinetics of electrocatalytic reactions

In this study,we systematically investigated the effect of proton concentration on the kinetics of the oxygen reduction reaction(ORR)on Pt(111)in acidic solutions.Experimental results demonstrate a rectangular hyperbolic relationship,i.e.,the ORR current excluding the effect of other variables increases with proton concentration and then tends to a constant value.We consider that this is caused by the limitation of ORR kinetics by the trace oxygen concentration in the solution,which determines the upper limit of ORR kinetics.A model of effective concentration is further proposed for rectangular hyperbolic relationships:when the reactant concentration is high enough to reach a critical saturation concentration,the effective reactant concentration will become a constant value.This could be due to the limited concentration of a certain reactant for reactions involving more than one reactant or the limited number of active sites available on the catalyst.Our study provides new insights into the kinetics of electrocatalytic reactions,and it is important for the proper evaluation of catalyst activity and the study of structureperformance relationships.

Deciphering the linear relationship in the activity of the oxygen reduction reaction on Pt electrodes:A decisive role of adsorbates

Despite substantial efforts in developing high-performance catalysts for the oxygen reduction reaction(ORR),the persistent challenge lies in the high onset overpotential of the ORR,and the effect of the elec-trolyte solution cannot be ignored.Consequently,we have systematically investigated the impact of adsorbate species and concentration,as well as solution pH,on the ORR activity on Pt(111)and Pt(poly)electrodes.The results all tend to establish a linear quantitative relationship between the onset potential for ORR and the adsorption equilibrium potential of the adsorbate.This finding indicates the decisive role of adsorbates in the onset potential for ORR,suggesting that the adsorption potential of adsorbates can serve as an intuitive criterion for ORR activity.Additional support for this conclusion is derived from experimental results obtained from the oxygen evolution reaction on Pt(poly)with different adsorbate species and from the hydrogen evolution reaction on Pt(111)with iodine adsorption.We further propose both an empirical equation for the onset potential for ORR and the concept of a potential-regulated adsor-bate shielding effect to elucidate the influence of adsorbates on ORR activity.This study provides new insights into the high onset overpotential of the ORR and offers potential strategies for predicting and enhancingORRactivity inthefuture.

A case of herpesviral corneal endotheliitis presenting with corneal endothelial defect

Dear Editor,Corneal endotheliitis,first reported in 1982 as an autoimmune disorder by Khodadoust and Attarzadeh[1],is now recognized to be frequently induced by viral infections,including varicella zoster virus(VZV),cytomegalovirus(CMV)and herpes simplex virus(HSV),that can cause inflammatory and immune-related injuries or direct damages to corneal endothelial cells[2-3].In cases with this type of endotheliitis of viral origin,manifestations may include conjunctival ciliary congestion or mixed congestion,corneal subepithelial bulla,localized corneal edema,keratic precipitates(KP)characteristic to the edema area,puckered posterior elastic lamina,mild anterior chamber reaction,intraocular pressure(IOP)elevation in presence of inflammation in trabecular meshwork,and endothelial decompensation[3-4].Accurate diagnosis of viral corneal endotheliitis is challenging due to its complex presentation,leading to a high misdiagnosis rate.To the best of our knowledge,there was no previous report of viral corneal endotheliitis presenting with corneal endothelial defects in the English literature.

Long noncoding RNA protein-disulfide isomerase-associated 3 regulated high glucose-induced podocyte apoptosis in diabetic nephropathy through targeting miR-139-3p

BACKGROUND Podocyte apoptosis plays a vital role in proteinuria pathogenesis in diabetic nephropathy(DN).The regulatory relationship between long noncoding RNAs(lncRNAs)and podocyte apoptosis has recently become another research hot spot in the DN field.AIM To investigate whether lncRNA protein-disulfide isomerase-associated 3(Pdia3)could regulate podocyte apoptosis through miR-139-3p and revealed the underlying mechanism.METHODS Using normal glucose or high glucose(HG)-cultured podocytes,the cellular functions and exact mechanisms underlying the regulatory effects of lncRNA Pdia3 on podocyte apoptosis and endoplasmic reticulum stress(ERS)were explored.LncRNA Pdia3 and miR-139-3p expression were measured through quantitative real-time polymerase chain reaction.Relative cell viability was detected through the cell counting kit-8 colorimetric assay.The podocyte apoptosis rate in each group was measured through flow cytometry.The interaction between lncRNA Pdia3 and miR-139-3p was examined through the dual luciferase reporter assay.Finally,western blotting was performed to detect the effect of lncRNA Pdia3 on podocyte apoptosis and ERS via miR-139-3p.RESULTS The expression of lncRNA Pdia3 was significantly downregulated in HG-cultured podocytes.Next,lncRNA Pdia3 was involved in HG-induced podocyte apoptosis.Furthermore,the dual luciferase reporter assay confirmed the direct interaction between lncRNA Pdia3 and miR-139-3p.LncRNA Pdia3 overexpression attenuated podocyte apoptosis and ERS through miR-139-3p in HG-cultured podocytes.CONCLUSION Taken together,this study demonstrated that lncRNA Pdia3 overexpression could attenuate HG-induced podocyte apoptosis and ERS by acting as a competing endogenous RNA of miR-139-3p,which might provide a potential therapeutic target for DN.

新生血管性年龄相关性黄斑变性治疗进展

年龄相关性黄斑变性是西方国家65岁以上人群视力损害和视力丧失的重要原因,是目前我国第三大致盲性眼病,主要影响中心视力。血管内皮生长因子在新生血管性年龄相关性黄斑变性的发病机制中起着重要的作用,目前抗血管内皮生长因子治疗已成为临床一线治疗方法。但仍有一部分患者需反复注射或不应答,因此需探索新的治疗方式进一步完善当前治疗,为今后新生血管性年龄相关性黄斑变性的治疗提供新思路。

Preparation of Surfactant-Free Pt and PtRu Nanoparticles with High Activity for Methanol Oxidation

A simple and green approach to synthesize highly active electro-catalysts for methanol oxi- dation reaction （MOR） without using any organic agents is described. Pt nanoparticles are directly deposited on the pre-cleaned and pre-oxidized multiwall carbon nanotubes （MWC- NTs） from Pt salt by using CO as the reductant. MOR activity has been characterized by both cyclic voltammetry and chronoamperometry, the current density and mass specific current at the peak potential （ca. 0.9 V vs. RHE） reaches 11.6 mA/cm^2 and 860 mA/mgpt, respectively. After electro-deposition of Ru onto the Pt/MWCNTs surface, the catalysts show steady state mass specific current of 20 and 80 mA/mgpt at 0.5 and 0.6 V, respectively.

Unravelling Hydrogen Adsorption Kinetics on Ir(111)Electrode in Acid Solutions by Impedance Spectroscopy

The kinetics for hydrogen(H)adsorption on Ir(111)electrode has been studied in both HClO_(4) and H_(2)SO_(4) solutions by impedance spectroscopy.In HClO_(4),the adsorption rate for H adsorption on Ir(111)increases from 1.74×10^(-8)mol·cm^(-2)·s^(-1) to 3.47×10^(-7)mol·cm^(-2)·s^(-1) with the decrease of the applied potential from 0.2 V to 0.1 V(vs.RHE),which is ca.one to two orders of magnitude slower than that on Pt(111)under otherwise identical condition.This is explained by the stronger binding of water to Ir(111),which needs a higher barrier to reorient during the under potential deposition of H from hydronium within the hydrogen bonded water network.In H_(2)SO_(4),the adsorption potential is ca.200 mV negatively shifted,accompanied by a decrease of adsorption rate by up to one order of magnitude,which is explained by the hindrance of the strongly adsorbed sulfate/bisulfate on Ir(111).Our results demonstrate that under electrochemical environment,H adsorption is strongly affected by the accompanying displacement and reorientation of water molecules that initially stay close to the electrode surface.

pH Effect on Oxidation of Hydrogen Peroxide on Au(111) Electrode in Alkaline Solutions

The hydrogen peroxide oxidation reaction (HPOOR) on Au(111) electrode in alkaline solutions with pH values ranging from 10 to 13 was examined systematically. HPOOR activity increased and the slope of the i-E curve decreased with increasing pH. HO2- is suggested to be the main reactive intermediate for HPOOR in alkaline media. The fast kinetics for HPOOR in alkaline solution is facilitated by the electrostatic interaction between the positively charged electrode and the reactive anions (i.e., HO2- and HO-), which increases the concentration of these reactants and the thermodynamic driving force for HO2- oxidation at the reaction plane.

Restructuring of well-defined Pt-based electrode surfaces under mild electrochemical conditions

Since the 1980s,single-crystal Pt electrodes with well-defined surface structures have been deemed stable under mild electrochemical conditions(e.g.,in the potential region of electric double layers,underpotential deposition of hydrogen,or mild hydrogen evolution/OH adsorption)and have served as model electrodes for unraveling the structure-performance relation in electrocatalysis.With the advancement of in situ electrochemical microscopy/spectroscopy techniques,subtle surface restructuring under mild electrochemical conditions has been achieved in the last decade.Surface restructuring can considerably modify electrocatalytic properties by generating/destroying highly active sites,thereby interfering with the deduction of the structure-performance relation.In this review,we summarize recent progress in the restructuring of well-defined Pt(-based)electrode surfaces under mild electrochemical conditions.The importance of the meticulous structural characterization of Pt electrodes before,during,and after electrochemical measurements is demonstrated using CO adsorption/oxidation,hydrogen adsorption/evolution,and oxygen reduction as examples.The implications of present findings for correctly identifying the reaction mechanisms and kinetics of other electrocatalytic systems are also briefly discussed.

Effect of mass transfer and solution composition on the quantification of reaction kinetics by differential electrochemical mass spectrometry

Differential electrochemical mass spectrometry(DEMS)is one of the most powerful techniques for both the mechanistic and kinetic study of complicated electrocatalytic reactions.It can provide information on the nature and yields of the products generated,their production rate,and the structure-activity relationship between the electrocatalysts and the target reactions.The precise calibration of the mass signal is a prerequisite for the accurate evaluation of reaction kinetics.In this work,we use the oxidation reactions of CO and HCOOH to demonstrate how certain conditions,such as the flow rate and solution composition,affect the collection efficiency and ionization probability of the species to be detected.These parameters can affect the determination of the mass calibration constant and the accuracy of the subsequent quantitative DEMS analysis.We show the relationship between the mass calibration constant and the flow rate,and provide strategies for eliminating this and the related problems.

Electrochemical Study on Hydrogen Evolution and CO2 Reduction on Pt Electrode in Acid Solutions with Different pH

Hydrogen evolution reaction(HER)is the major cathodic reaction which competes CO2 reduction reaction(CO2 RR)on Pt electrode.Molecular level understanding on how these two reactions interact with each other and what the key factors are of CO2 RR kinetics and selectivity will be of great help in optimizing electrolysers for CO2 reduction.In this work,we report our results of hydrogen evolution and CO2 reduction on Pt(111)and Pt film electrodes in CO2 saturated acid solution by cyclic voltammetry and infrared spectroscopy.In solution with pH>2,the major process is HER and the interfacial pH increases abruptly during HER;COad is the only adsorbed intermediate detected in CO2 reduction by infrared spectroscopy;the rate for COad formation increases with the coverage of UPD-H and reaches maximum at the onset potential for HER;the decrease of COad formation under HER is attributed to the available limited sites and the limited residence time for the reduction intermediate(Had),which is necessary for CO2 adsorption and reduction.

Electrochemical CO2 Reduction on Pd-Modified Cu Foil

Bimetallic catalysts can improve CO2 reduction efficiency via the combined properties of two metals.CuPd shows enhanced CO2 reduction activity compared to copper alone.Using differential electrochemical mass spectrometry(DEMS)and electrochemical infrared(IR)spectroscopy,volatile products and adsorbed intermediates were measured during CO2 and CO reduction on Cu and CuPd.The IR band corresponding to adsorbed CO appears 300 mV more positive on CuPd than that on Cu,indicating acceleration of CO2 reduction to CO.Electrochemical IR spectroscopy measurements in CO-saturated solutions reveal similar potentials for CO adsorption and CO3^2-desorption on CuPd and Cu,indicating that CO adsorption is controlled by desorption of CO3^2-.DEMS measurements carried out during CO reduction at both electrodes showed that the onset potential for reduction of CO to CH4 and CH3OH on CuPd is about 200 mV more positive than that on Cu.We attribute these improvements to interaction of Cu and Pd,which shifts the d-band center of the Cu sites.

Identifying Diffusion Limiting Current to Unravel the Intrinsic Kinetics of Electrode Reactions Affected by Mass Transfer at Rotating Disk Electrode

Rotating disk electrode systems are widely used to study the kinetics of electrocatalytic reactions that may suffer from insufficient mass transfer of the reactants.Kinetic current density at certain overpotential calculated by the Koutecky-Levich equation is commonly used as the metrics to evaluate the activity of electrocatalysts.However,it is frequently found that the diffusion limiting current density is not correctly identified in the literatures.Instead of kinetic current density,the measured current density normalized by diffusion limiting current density(j/jL)has also been frequently under circumstance where its validity is not justified.By taking oxygen reduction reaction/hydrogen oxidation reaction/hydrogen evolution reaction as examples,we demonstrate that identifying the actual diffusion limiting current density for the same reaction under otherwise identical conditions from the experimental data is essential to accurately deduce kinetic current density.Our analysis reveals that j/jLis a rough activity metric which can only be used to qualitatively compare the activity trend under conditions that the mass transfer conditions and the roughness factor of the electrode are exactly the same.In addition,if one wants to use j/jLto compare the intrinsic activity,the concentration overpotential should be eliminated.

Effect of Sulfate Adlayer on Formic Acid Oxidation on Pd(111) Electrode

The kinetics of formic acid oxidation (FAO) on Pd(111) in 0.1 mol/L H2SO4+0.1 mol/L HCOOH with and without addition of Na2SO4 is studied using cyclic voltammetry and potential step method, which is compared with that in 0.1 mol/L HClO4. It is found that adsorbed sulfate has significant inhibition effect on FAO kinetics. After addition of 0.05 mol/L or 0.1 mol/L Na2SO4, FAO current in the negative-going scan is found to be significantly smaller than that at the same potential in the positive-going scan. We speculate that at potentials positive of the phase transition potential for the (SO4*ad)m+[(H2O)n-H3O+] or(SO4*ad)m+[Na+(H2O)n-H3O+] adlayer, the adlayer structure probably becomes denser and more stable with the increase of potential or with the addition of Na2SO4. The formation of connected adlayer network greatly enhance the stability of the adlayer, and the insertion of positive-charged H+ or Na+ into the adlayer network further reduces the electrostatic repulsion between partially charged sulfates. As a result, the destruction/desorption of compact sulfate adlayer becomes more difficult, which leaves much less free sites on the surface for FAO, and thus FAO kinetics at higher potentials and in the subsequent negative-going potential scan is significantly inhibited.

In Situ HRTEM Observation of Electron-Irradiation-Induced Amorphization and Dissolution of the E(Al_(18)Cr_2Mg_3) Phase in 7475 Al Alloy

Electron irradiation effects on phase stability of the E （Al18Cr2Mg3） phase have been investigated by high- angle annular dark-field scanning transmission electron microscopy and high-resolution transmission electron microscopy （HRTEM）. The in situ HRTEM observations show that the Ala8Cr2Mg3 particles with different thickness undergo amorphization and dissolution under 300 keV electron irradiation at 25 ℃. The results indicate that the intermetallic compound Al18Cr2Mg3 is unstable under electron irradiation, and structural changes mainly depend on the thickness of particles. Amorphization in the thick particles is caused by a combination of chemical disordering and an increase in point defect concentration. Dissolution after amorphization in the thin particles is attributed to the diffusion of point defect towards the Al matrix.

Fhe risk of human papillomavirus infection for male ertility abnormality： a meta-analysis

Human papillomavirus （HPV） is the most common sexually transmitted virus in males and females worldwide; yet its impact upon male fertility remains unclear. The objective of this study was to evaluate the potential impact of HPV infection in semen on male fertility abnormality. A systematic literature search was performed in PubMed, Medline, Embase, Web of Science, and the Cochrane Library database for relevant publications up to May 6,2017. The odds ratio （OR）, and its corresponding 95% confidence interval （CI）, was selected to represent the effect size. Statistical analysis was conducted using STATA 12.0. In total, eight articles, providing data on 1955 participants, were included in this meta-analysis. Collectively, the data suggested that HPV infection of semen was a risk factor for male fertility abnormality with an OR of 3.02 （95% Ch 2.11-4.32; I2= 6.9%）. Sensitivity analysis revealed that the results of this study were robust. In conclusion, HPV infection of semen represents a risk factor for male fertility abnormality.

Effects of an odd particle on shape phase transitions in odd-even systems

A scheme to solve the Hamiltonian in the interacting boson-fermion model in terms of the SU(3)coupling basis is introduced,through which the effects of an odd particle on shape phase transitions(SPTs)in odd-A nuclei are examined by comparing the critical behaviors of some selected quantities in odd-even and even-even systems.The results indicate that the spherical to prolate(U(5)-SU(3))SPT and spherical to γ-soft (U(5)-O(6))SPT may clearly occur in the odd-even system with the SPT signatures revealed by various quantities including the excitation energies,energy ratio,B(E2)ratio,quadrupole moments,and one-particle-transfer spectroscopic intensities.In particular,the results indicate that the spherical to prolate SPT in the odd-even system can even be strengthened by the effects of the odd particle with the large fluctuations of the quadrupole deformations appearing near the critical point.

Effect of Ag on the Microstructure,Mechanical and Bio-corrosion Properties of Fe–30Mn Alloy

In the current work, biodegradable Fe–30 Mn– X Ag( X = 1, 2, 5, 10 wt%) alloys were prepared by the rapid solidifi cation with copper-mold-casting technology. Phase analysis demonstrates that Fe–30 Mn– X Ag alloys consist of austenite γ phase with a fcc structure and martensite ε phase with a hcp structure. The yield strength of the samples increases with increasing Ag contents. Compared with Fe–30 Mn alloy, the degradation rates of Fe–30 Mn– X Ag in Hank’s solution are signifi cantly improved. Cytotoxicity evaluation reveals that the Fe–30 Mn–1 Ag and Fe–30 Mn–2 Ag alloys perform less toxicity on the Human Umbilical Vein Endothelial Cells(HUVEC), while Fe–30 Mn–5 Ag and Fe–30 Mn–10 Ag alloys perform no toxicity on it. The contact angles of deionized water on the Fe–30 Mn– X Ag alloy surface were ranged from 55° to 69°, which is benefi cial to the adhesion and growth of the cells. Besides, the addition of Ag leads to a much lower M/H slope, particularly for the Fe–30 Mn–5 Ag alloy exhibiting a non-magnetic property as SS316 L. Therefore, the present Fe–30 Mn– X Ag alloys would be potential candidates for degradable metals.

The determination of thermal junction potential difference

A novel method has been designed and exploited to determine the thermal junction potential difference(TJPD) between two acids or alkalies of the same composition but with different temperature. The absolute value of measured TJPD between two strong acids(or alkalies) maintained at different temperatures increases with increasing of the temperature difference between the two electrolytes over the range from 0 to 40 °C. In strong acids, the hot end always has the lower potential while in strong alkalies, the cold end has the lower potential. This is because the ions of fast diffusion rate contribute most to the TJPD. Our results demonstrate the importance of the correction for TJPD in deriving the kinetic parameters when studying the temperature effect on reaction kinetics.