Single atom Cu-N-C catalysts for the electro-reduction of CO_(2) to CO assessed by rotating ring-disc electrode

The electrochemical CO_(2) reduction reaction(CO_(2)RR) to controllable chemicals is considered as a promising pathway to store intermittent renewable energy. Herein, a set of catalysts based on copper-nitrogendoped carbon xerogel(Cu-N-C) are successfully developed varying the copper amount and the nature of the copper precursor, for the efficient CO_(2)RR. The electrocatalytic performance of Cu-N-C materials is assessed by a rotating ring-disc electrode(RRDE), technique still rarely explored for CO_(2)RR. For comparison, products are also characterized by online gas chromatography in a H-cell. The as-synthesized Cu-NC catalysts are found to be active and highly CO selective at low overpotentials(from -0.6 to -0.8 V vs.RHE) in 0.1 M KHCO_(3), while H_(2) from the competitive water reduction appears at larger overpotentials(-0.9 V vs. RHE). The optimum copper acetate-derived catalyst containing Cu-N_(4) moieties exhibits a CO_(2)-to-CO turnover frequency of 997 h^(-1) at -0.9 V vs. RHE with a H_(2)/CO ratio of 1.8. These results demonstrate that RRDE configuration can be used as a feasible approach for identifying electrolysis products from CO_(2)RR.

Investigation on the Electrochemical Polymerization of Catechol by Means of Rotating Ring-disk Electrode

The electrolysis of catechol was studied in the pH values of 1 to 10. The results from the rotating ring disk electrode (RRDE) experiments show that at low pH values, the electrochemical polymerization of catechol was performed by one step, and at higher pH values, the electrochemical polymerization of catechol was carried out by two steps, i.e . oxidation of catechol and followed by polymerization. The intermediates generated at the disk were detected at the ring electrode in the ring potential region of -0.2 to 0 V (vs. Ag/AgCl). One of reasons for the decrease in the ratio of i r to i d with increasing the ring potential is caused by formation of positively charged intermediates at the disk electrode. This ratio increases with increasing the rotation rate of the RRDE, which indicates that the intermediates are not stable. A shielding effect during polymerization of catechol was observed when the ring potential was set at 0.1 V (vs. Ag/AgCl). The electron spin resonance (ESR) of polycatechol shows that polycatechol possesses unpaired electrons. The images of polycatechol films synthesized at different conditions are described.

Shape memory TiNi powders produced by plasma rotating electrode process for additive manufacturing

This study aimed to produce spherical TiNi powders suitable for additive manufacturing by plasma rotating electrode process(PREP).Scanning electron microscopy,X-ray diffractometry and differential scanning calorimetry were used to investigate the surface and inner micro-morphology,phase constituent and martensitic transformation temperature of the surface and inner of the atomized TiNi powders with different particle sizes.The results show that the powder surface becomes smoother and the grain becomes finer gradually with decreasing particle size.All the powders exhibit a main B2-TiNi phase,while large powders with the particle size≥178μm contain additional minor Ti2Ni and Ni3Ti secondary phases.These secondary phases are a result of the eutectoid decomposition during cooling.Particles with different particle sizes have experienced different cooling rates during atomization.Various cooling rates cause different martensitic transformation temperatures and routes of the TiNi powders;in particular,the transformation temperature decreases with decreasing particle size.

Electrowinning of Copper Using Rotating Cylinder Electrode Utilizing Lead Anode

The effect of lead anode, rotating cylinder electrode (RCE), amount of 1,2-dihydroxypropane (12-DHP), temperature and rotation on the electrowinning of copper from low concentration acidified copper sulphate solution has been investigated. Copper powder was electrodeposited onto RCE that made of pure copper. From cyclic voltammetry experiments, an empirical parameter called the departure percent, S, was obtained which may represent the stability of the organic additive in the given medium and under the experimental conditions. The inhibition percentage, P, was 0.00 - 89.91% depending on the experimental variables. P was affected by temperature and mole fraction of 12-DHP, while rotation did not show any influence on it. Values of activation energy of electrodeposition process, Ea, were found to be less than 28 kJ mol-1 indicating diffusion controlled process. The overall mass transfer correlations under the present conditions have been computed using the dimensional analysis method. The data were valid for 90 < Sh < 1098, 737 < Sc < 59284 and 271 < Re < 7046 and the results agreed with the previous studies of mass transfer to rotating cylinders in turbulent flow regimes. The effect of time, content of 12-DHP, temperature and the speed of rotation on the morphological changes of the electrodeposited copper powder as well as deposits composition and crystallite size have been studied. Various crystallite sizes ranged 7.1 nm - 250.6 nm were obtained and characterized by EDS and XRD. Different topographs proved that the rate of copper electrodeposition increased by increasing deposition time, temperature and the speed of rotation. Also, they proved that the deposition rate decreased by adding 12-DHP to the solution. Therefore, the results obtained by SEM supported those achieved by measuring the limiting current density and follow the normal manner when organic solvents were added to the electrodeposition bath.

Electrochemical oxidation of sodium sulfide on rotating ring-disc electrode

A rotating ring (Pt) disc (Pt) electrode was employed to investigate the oxidation process of sodium sulfide (Na 2S). It was reported that the oxidation intermediates and product of HS - were formed on the disc electrode and then reduced on the ring electrode. The results indicate that at a rotation rate of 20 Hz, when the disc electrode potential was -0.15 V (vs SHE) and higher, more extensive oxidation process took place via a series of electrochemical steps to produce sulfur (S). The products of oxidation intermediates (S 2- x , S 2- 2) and sulfur (S) reduced either on the ring electrode with a set potential of -0.8 V (vs SHE), or on disc electrode with negative going potential sweep at about -0.5～ 0.55 V (vs SHE). The experimental results of voltammogram of ring disc electrode at sodium sulfide solution demonstrated that the first step was the oxidation of HS - and produce S 2- x , and then the S 2- x adsorbed integrated itself and formed sulfur (S).

Investigations of Thallium(Ⅰ) Underpotential Deposition on the Silver Rotating Disk Electrode and Its Analytical Application

The cyclic voltammetry(CV) and the square wave technique were used for the investigations of thallium(Ⅰ) underpotential deposition(UPD) on the silver electrode. A solution of 10 \{mmol/L\} HClO 4+10 mmol/L NaCl was selected as the supporting electrolyte. The calibration plots for Tl(Ⅰ) concentration in the range of 2×10 -9 -1×10 -7 mol/L were obtained. The detection limit was 5×10 -10 mol/L. For the solutions of 4 0×10 -9 mol/L thallium added before the urine sample pretreatment procedure, the average recovery was 105 6% with a relative standard deviation(RSD) of 15 5%.

A Study of Making Iron Aluminide Alloy Powders with New Rotating Electrode Technology

A new process was used for producing FeAl alloy pow de rs with double consumable rotating electrodes and the powders made in this appar atus were analyzed. In this new technology, tungsten rod serves as a cathode ele ctrode, while the alloy rod as an anode electrode. The conventional rotating ele ctrode process must have an anode with pre-melting alloys; however, in this new process, using pure iron as cathode electrode and pure aluminum as anode electr ode can eliminate the step of pre-melting. The effects of process variables, which include electrode rotational speed, a nd electrode diameter of the mean particle diameter were determined. Results showed that both the rotational speed and diameter of electrodes would a ffect the mean diameter of particles. There are three kinds of powders with diff erent composition produced in this study and the possible mechanisms are discuss ed. The process parameters and volume mean diameter of the powders have been cor related to find an experimental equation. The results show that when the rotational speed and the diameter of the anode el ectrode are increased, the powders size will decrease. However, the powders size will increase with cathode electrode.

Generation of atmospheric pressure air diffuse discharge plasma in oxygen enriched working gas with floating electrode

In this work,a floating electrode is employed to generate a stable large-area diffuse discharge plasma under an open oxygen-rich environment.The discharge image and the optical emission spectra of the N2(C-B),N2+(B-X),N2(B-A),and O(3p–3s,777 nm)are measured to analyze the morphological and optical characteristics of the discharge.The effects of applied voltage,gas flow rate,and electrode gap on the reactive species,vibrational temperature and rotational temperature are investigated,and the discharge mode is discussed by simulating the electrostatic field before the breakdown.It is found that the changes of applied voltage and electrode gap causes the transition of the discharge modes among corona mode,diffuse discharge mode and spark mode.It is shown that the floating electrode can inhibit the transition from discharge to spark mode to a certain extent,which is conducive to maintaining the stability of discharge.As is vividly illustrated in this study,the increase of applied voltage or the decrease of electrode gap contributes to the generation of more active particles,such as N2(C)andN+2(B).Furthermore,the Joule heating effect becomes more evident with the increased applied voltage when the electrode gap is 15 and 20 mm.Moreover,as the applied voltage increases,the vibrational temperature increases at the electrode gap of 25 mm.

Influence of Relative Electrode-Electrolyte Movement over Productivity for Silver Recovery from Diluted Solutions

The paper presents the influence of relative electrode-electrolyte movement over productivity for silver ions recovery by electrodeposition from diluted solutions. Wasted photographic fixing agent solution in various concentrations was used. For each concentration three regimes were studied： stationary, electrode rotation with 100 rpm and electrode rotation with 300 rpm. Polarization curves were drawn and working conditions from silver recovery point of view were discussed.

Solidification Behavior and Microstructures Characteristics of Ti-48Al-3Nb-1.5Ta Powder Produced by Supreme-Speed Plasma Rotating Electrode Process

In this study,the characteristics and solidification behavior of Ti-48Al-3Nb-1.5Ta powder produced by supreme-speed plasma rotating electrode process(SS-PREP®)were investigated.The microstructure,phase and characteristics were analyzed by scanning electron microscopy,X-ray diffraction and other methods.The atomization mechanism is direct drop formation.The relationship between the particle size and cooling rate is vc=3.14×10^(-7)·d^(-2)+1.18×10^(-2)·d^(3/2),and the relationship between secondary dendrite arm space and the particle size isλ=0.028d+0.11,as well as the relationship between SDAS and cooling rate isλ=4.84×10^(-5)·T^(-1.43).With increase in particle size,the surface structure gradually changes from the featureless smooth structure to dendritic and cellular dendritic morphology,and the flow ability becomes better.The carbides mainly exist within 5 nm of the surface and the oxidation layer is about 20 nm thick.Ti-48Al-3Nb-1.5Ta powder was mainly composed ofα2 phase andγphase.With increase in particle size,the content ofγphase increases,and the hardness decreases accordingly.The 106–250μm particles are composed of multiple grains with the grain size of 70–80μm.The microstructure,phase composition and hardness of different TiAl powders with the same size are similar,but the elastic modulus is different.

基于旋转圆柱三电极阵列的覆冰测量方法

覆冰严重会影响电网安全稳定运行,输配电装备的覆冰监测是电网冰灾防御的前提。为此,基于冰层的电容效应提出一种旋转圆柱三电极阵列覆冰测量方法。首先,推导电容值与覆冰厚度计算公式,从理论上说明该方法的可行性;其次,建立圆柱三电极阵列有限元模型并对其结构参数进行有限元数值计算;再次,以信号强度、灵敏度与穿透深度为评价指标对圆柱三电极阵列选取合适参数;最后,在野外自然环境下对旋转圆柱三电极阵列覆冰测量装置进行试验。仿真和试验结果表明,在穿透深度以内,旋转圆柱三电极阵列能够较为准确地测量覆冰厚度、分辨覆冰类型。在雨凇、混合凇覆冰条件下,覆冰电容值平均误差最大为4.83%,能够满足覆冰厚度的测量要求。该文为输配电装备覆冰监测提供了一种新型装置与测量方法,未来有望应用于架空线路覆冰在线监测。

铝合金深盲小孔管电极电解加工试验研究

针对瓶口阀铝合金阀体深盲小孔难加工问题,应用管电极电解加工方法解决该问题。为提高铝合金深盲小孔管电极电解加工稳定性,仿真分析了不同电极进给速度下加工间隙内电场、流场的分布规律;以6061铝合金为对象,使用内径为0.6 mm、外径为1.0 mm的管电极进行电解加工,研究了初始间隙、电极进给速度以及电极旋转对管电极电解加工的影响。仿真和试验结果表明,电极进给速度过大或过小,均不利于铝合金深盲小孔的稳定加工,电极进给速度大于1.4 mm/min时孔底易形成凸起,电极进给速度小于1.0 mm/min时孔底易形成凹坑;初始间隙取0.3 mm能获得质量更好的孔口形貌;电极旋转有利于产物和热量的排出,从而提高加工精度。采用最优参数加工得到了孔间距为2.46 mm、平均直径为1.28 mm的密集孔和平均直径为1.29 mm、深度为50 mm的深盲小孔。

EIGA和PREP制备M62轴承钢粉末

采用电极感应熔炼气雾化法(electrode induction melting gas atomization,EIGA)和等离子旋转电极雾化法(plasma rotating electrode process,PREP)分别制备出了高纯度M62轴承钢粉末,利用激光粒度分析仪、氧氮分析仪、扫描电子显微镜对M62轴承钢粉末的粒径分布、氮氧含量、微观形貌进行了对比分析。结果表明:两种粉末都以球形粉为主,其中PREP制备的粉末(M62-PREP)球形度更高,而EIGA制备的粉末(M62-EIGA)中卫星粉和不规则粉末的比例较多;M62-PREP粉末的中值粒度(D50)为108.11μm,明显高于M62-EIGA粉末的中值粒度(D50=38.68μm)。两种粉末成分分布均匀,无明显元素偏析,其中M62-EIGA粉末颗粒内部的晶粒更细,两种粉末都具有良好的流动性。预合金电极棒、M62-PREP粉末、M62-EIGA粉末的N含量(质量分数)分别为0.0070%、0.0072%、0.0068%,N元素的含量变化不大;M62-PREP粉末的O含量(质量分数)由预合金电极棒的0.0008%增加到了0.0035%,而M62-EIGA粉末的O含量增加到了0.0089%,粉末中O含量明显增多。对热等静压后的烧结试样进行了夹杂物分析,M62-EIGA粉末轴承钢中大尺寸含氧夹杂物数量更多,选用M62-PREP粉末轴承钢应有更好的性能。

旋转圆盘电极原子发射光谱法检测变压器油中金属及污染物元素含量及其不确定度评估

本文采用旋转圆盘电极原子发射光谱法(RDE-AES)测定变压器绝缘油中银、铝、钡等21种金属及污染物元素含量,考察了圆盘电极浸油深度以及油样均匀化方式对检测结果的影响,并用标准油和绝缘油样品对实验方法进行了验证。结果表明:当选择圆盘电极浸油深度为其直径的1/3时,超声3 min且用力摇匀后检测,检测结果相对误差较小。各元素检出限为0~1.07μg/g,相对标准偏差(RSD,n=6)为0.7%~2.9%,除V元素外,其他20种元素加标回收率为96.64%~110.01%。对绝缘油中P元素含量进行A类和B类不确定度评定,并对各分量不确定度进行合成和扩展,得到不确定度为(8.34±1.06)μg/g(k=2),此不确定度主要来源于工作曲线的标准油样、测量重复性和日常标准化过程。

PREP工艺参数对GH3536高温合金粉末性能的影响

采用等离子旋转电极雾化法(Plasma Rotating Electrode Process,PREP)制备GH3536合金粉末,探究电极棒旋转速度和电流强度对粉末粒度及其物性能的影响。结果表明,粉末平均粒径随着旋转速度的提高而减小,当旋转速度为16000 r·min^(-1)时,粉末的D50粒径最小为27μm。在棒料转速一定时,随着主弧电流强度的增加,粉末的平均直径逐渐增大,当电流强度由1300 A提高至1500 A时,粉末D50粒度从33μm增加至42μm。此外,棒料旋转速度和主弧电流的增加能够改善GH3536粉末的流动性与松装密度。经过综合考虑,旋转速度14000 r·min^(-1)、电流1300 A、进给速度0.8 mm·s^(-1)工艺的参数组合最为适宜。

Koutecky-Levich analysis applied to nanoparticle modified rotating disk electrodes： Electrocatalysis or misinterpretation？

The application of naive Koutecky-Levich analysis to micro- and nano-particle modified rotating disk electrodes of partially covered and non-planar geometry is critically analysed. Assuming strong overlap of the diffusion fields of the particles such that transport to the entire surface is time-independent and one-dimensional, the observed voltammetric response reflects an apparent electrochemical rate o constant koapp, equal to the true rate constant ko describing the redox reaction of interest on the surface of the nanoparticles and the ratio,ψ, of the total electroactive surface area to the geometric area of the rotating disk surface. It is demonstrated that Koutecky-Levich analysis is applicable and yields the expected plots of I-1 versus ω-1 where I is the current and ω is the rotation speed but that the values of the electrochemical rate constants inferred are thereof koapp, not ko. Thus, for ψ 〉 1 apparent electrocatalysis might be naively but wrongly inferred whereas for ψ 〈 1 the deduced electrochemical rate constant will be less than ko. Moreover, the effect of ψ on the observed rotating disk electrode voltammograms is significant, signalling the need for care in the overly simplistic application of Koutecky-Levich analysis to modified rotating electrodes, as is commonly applied for example in the analysis of possible oxygen reduction catalysts.

Analysis and control of inter-electrode gap during leveling process in counter-rotating electrochemical machining

The inter-electrode gap(IEG) is an essential parameter for the anode shaping process in electrochemical machining(ECM) and directly affects the machining accuracy. In this paper, the IEG during the leveling process of an oval anode workpiece in counter-rotating ECM(CRECM)is investigated. The variation of the minimum IEG is analyzed theoretically, and the results indicate that rather than reaching equilibrium, the minimum IEG in CRECM expands constantly when a constant feed speed is used for the cathode tool. This IEG expansion leads to a poor localization effect and has an adverse influence on the roundness of the machined workpiece. To maintain a small constant IEG in CRECM, a variable feed speed is used for the cathode based on a fitted equation. The theoretical results show that the minimum IEG can be controlled at a small value by using an accelerated feed speed. Experiments have been conducted using a specific experimental apparatus in which the cathode tool is designed as a combined structure of two sectors and a thin sheet. By detecting the machining currents flowing through the minimum IEG, how the latter varies is obtained indirectly. The results indicate that using an accelerated feed speed is effective for controlling the IEG, thereby improving the roundness of the machined workpiece.

Effect of Rotation Rate on the Formation of Platinum-modified Polyaniline Film and Electrocatalytic Oxidation of Methanol

The oxidation of methanol was investigated on platinum-modified polyaniline electrode. Changes in the electrode rotation rates (Ω) during platinum electrodeposition remarkably affect the formation and distribution of platinum in the polymer matrix and consequently lead to different currents of methanol oxidation. The results show that platinum loading is proportional to rotation ratesΩ1/2.

小电流下弧根运动对空气直流电弧的影响

阴极弧根为电子发射的主要区域,弧根的运动对空气直流电弧等离子体特性有重要意义。通过电极旋转驱动阴极弧根运动,实验观测得到电极旋转情况下空气直流电弧拉弧过程电极表面烧蚀情况、扭曲的弧柱形态,同时提取并对比了直线拉弧和旋转拉弧的电弧电压上升曲线。参照临界电流试验条件,建立小电流下平行电极间三维电弧仿真模型,探究在小电流情况下,自由燃烧态电弧的演变过程。仿真结果表明:阴极弧根运动使得发射后极间带电粒子空间分布变化,间隙放电通道改变,电弧的最大温度值降低;当电弧放电通道不稳定时,极间电弧电压出现波动,电弧能量包络空间相对变小,间隙中高能粒子较少,有利于电弧能量的空间逸散。

等离子旋转电极雾化制粉研究现状

等离子体旋转电极制备的合金粉末具有空心粉末少、化学纯度高、球形度高、尺寸分布窄等优点,但细粉的低生产率限制了其发展。为了深入分析等离子体旋转电极雾化的制粉过程,改善制粉工艺并提高细粉生产率,综述了等离子旋转电极雾化机理、数值模拟及工艺参数对粉末影响的研究进展,指出粉末通常表现为液线破碎模式与直接液滴形成模式,提升转速与增加电流强度可提高细粉生产率,而等离子旋转电极雾化制粉过程的数值模拟还有待进一步研究。