Degradation of Phenol by Hydroxyl Radicals on Different Coating Lead Dioxide Electrodes

Lead dioxide electrodes on Ti substrates were prepared by thermal-deposition or electro-deposition. The amount of hydroxyl radicals generated at the electrodes prepared by the above-mentioned two methods was compared with that at the electrodes mingled with Bi or La prepared by electro-deposition. The experimental results indicate that the highest concentration of hydroxyl radicals generated by thermal-deposition, electro-deposition mingled with nothing, electro-deposition mingled with Bi or La was 0.781, 1.048, 1.838 or 2.044 μmol/L, respectively. When phenol was electrolyzed on the four electrodes at a current density of 30 mA/cm2, the removal efficiency of phenol after electrolysis for 1.5 h was 87.30%, 93.55%, 97.95% or 98.70%, TOC removal efficiency after electrolysis for 5 h was 86.76%, 94.26%, 98.53% or 99.60%, respectively. Through the degradation experiments of phenol, the amount of hydroxyl radicals was responsible for the removal efficiency of phenol. The electro-catalytic characteristics were investigated by SEM, the generation amount of hydroxyl radicals, the degradation degree of phenol and the stability and conductivity of the electrodes were also investigated. The experimental results indicate that the four electrodes all show good electro-catalytic characteristics; the electro-catalytic characteristics of the electrode mingled with La were superior to those of the other three ones, and the electrochemical degradation of phenol followed one-step reaction dynamics.

Surface treatment of titanium dioxide nanopowder using rotary electrode dielectric barrier discharge reactor

Titanium dioxide(Ti O_(2))nanopowder(P-25;Degussa AG)was treated using dielectric barrier discharge(DBD)in a rotary electrode DBD(RE-DBD)reactor.Its electrical and optical characteristics were investigated during RE-DBD generation.The treated TiO_(2)nanopowder properties and structures were analyzed using x-ray diffraction(XRD)and Fourier-transform infrared spectroscopy(FTIR).After RE-DBD treatment,XRD measurements indicated that the anatase peak theta positions shifted from 25.3°to 25.1°,which can be attributed to the substitution of new functional groups in the TiO_(2)lattice.The FTIR results show that hydroxyl groups(OH)at 3400 cm-1 increased considerably.The mechanism used to modify the TiO_(2)nanopowder surface by air DBD treatment was confirmed from optical emission spectrum measurements.Reactive species,such as OH radical,ozone and atomic oxygen can play key roles in hydroxyl formation on the TiO_(2)nanopowder surface.

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.

Electrosynthesis and physicochemical properties ofα-PbO_2-CeO_2-TiO_2 composite electrodes

In order to investigate the effect of solid particles dopants on physicochemical properties of α-PbO2 electrodes, a-PbO2 composite electrodes doped with nano-TiO2 and nano-CeO2 particles were respectively prepared on A1/conductive coating electrodes in 4 mol/L NaOH solution with addition of PbO until saturation by anodic codeposition. The electrodeposition mechanism, morphology, composition and structure of the composite electrodes were characterized by cyclic voltarnmogram （CV）, SEM, EDAX and XRD. Results show that the doping solid particles can not change reaction mechanism of α-PbO2 electrode in alkaline or acid plating bath, but can improve deposition rate and reduce oxygen evolution potential. The doping solid particles can inhibit the growth of a-PbO2 unit cell and improve specific surface area. The diffraction peak intensity of a-PbO2-CeO2-TiO2 composite electrode is lower than that of pure a-PbO2 electrode. The electrocatalytic activity of a-PbO2-2.12%CEO2-3.71%TIO2 composite electrode is the best. The Guglielmi model for CeO2 and TiO2 codeposition with a-PbO2 is also pronosed.

Composite Electrodeposited PbO2/Co3O4 on a Ti Substrate as Positive Electrode Materials for a Hybrid Supercapacitor

PbO2/Co3O4 composites were prepared on a Ti substrate by means of a composite electrodeposition method in Pb2+ plating solution containing dissolved nano-Co3O4 particles. X-ray diffraction（XRD）, scanning electron microscopy（SEM）, energy dispersive spectrometry（EDS） and transmission electron microscopy（TEM） were used to characterize the chemical composition and morphology of the PbO2/Co3O4 composites. The electrochemical and capacitance performance of the composites were investigated by cyclic voltammetry（CV）, charge-discharge tests and electrochemical impedance（EIS）. The results indicate that the composites comprise rutile phase Co3O4 and β-PbO2. In addition, the surface of the composite electrode is rough and porous. The PbO2/Co3O4 composites exhibit a high specific capacitance up to 215 F/g, which is ten times higher than that of the pure-PbO2 and two times higher than that of the pure-Co3O4 in 1 mol/L NaOH electrolytes.

Identifying the active sites in C-N codoped TiO_(2) electrode for electrocatalytic water oxidation to produce H_(2)O_(2)

Unveiling the active site of an electrocatalyst is fundamental for the development of efficient electrode material.For the two-electron water oxidation to produce H_(2)O_(2),competitive reactions,including four-and one-electron water oxidation and surface reconstruction derived from the high-oxidative environment co-existed,leading to great challenges to identify the real active sites on the electrode.In this work,Ti/TiO_(2)-based electrodes calcined under air,nitrogen,or urea atmospheres were selected as electrocatalysts for two-electron water oxidation.Electrochemical analyses were applied to evaluate the catalytic activity and selectivity.The morphological and current change on the electrode surface were determined by scanning electrochemical microscopy,while the chemical and valence evolutions with depth distributions were tested by XPS combined with cluster argon ion sputtering.The results demonstrated that Ti/TiO_(2) nanotube arrays served as the support,while the functional groups of carbonyl groups and pyrrolic nitrogen derived from the co-pyrolysis with urea were the active sites for the H_(2)O_(2) production.This finding provided a new horizon to design efficient catalysts for H_(2)O_(2) production.

Effects of sintering temperature on microstructure and performance of Ti-based Ti-Mn alloy anodic material

A novel Ti-based Ti-Mn composite anode used for electrolytic manganese dioxide(EMD) fabrication was developed by a two-step heating manganizing technique.The effects of sintering temperature on the manganized microstructure and the performance of the composite anode were studied by scanning electron microscopy(SEM),mechanical properties tests at room temperature and electrochemical methods.The results show that the thickness of the diffusion layer increases with the increase of sintering temperature up to 1 100 °C;whereas,the surface Mn content increases and reaches the maximum at 1 000 °C and then decreases thereafter.Lower surface Mn content is beneficial for the enhanced corrosion resistance and lowered open cell voltage in electrolytic process.The new anode prepared under the optimized conditions has been applied in industry and exhibits superior economic benefits to conventional Ti anodic materials.

Revealing the role of electrode potential micro-environments in single Mn atoms for carbon dioxide and oxygen electrolysis

Elucidation the relationship between electrode potentials and heterogeneous electrocatalytic reactions has attracted widespread attention.Herein we construct the well-defined Mn single-atom(MnSA)catalyst with four N-coordination through a simple thermal pyrolysis preparation method to investigate the electrode potential micro-environments effect on carbon dioxide reduction reactions(CO_(2)RR)and oxygen reduction reactions(ORR).MnSA catalysts generate higher CO production Faradaic efficiency of exceeding 90%at-0.9 V for CO_(2)RR and higher H_(2)O_(2)yield from 0.1 to 0.6 V with excellent ORR activity.Density functional theory(DFT)calculations based on constant potential models were performed to study the mechanism of MnSA on CO_(2)RR.The thermodynamic energy barrier of CO_(2)RR is lowest at-0.9 V vs.reversible hydrogen electrode(RHE).Similar DFT calculations on the H_(2)O_(2)yield of ORR showed that the H_(2)O_(2)yield at 0.2 V was higher.This study provides a reasonable explanation for the role of electrode potential micro-environments.

Correlation between impedance spectroscopy and bubble-induced mass transport in the electrochemical reduction of carbon dioxide

In the electrochemical conversion of carbon dioxide, high currents need to be employed to obtain large production rates, thus implying that mass transport of reactants and products is of crucial importance.This aspect can be investigated by employing a model that depicts the local environment for the reduction reactions. Simultaneously, electrochemical impedance spectroscopy, despite being a versatile technique, has rarely been adopted for studying the mass transport features during the carbon dioxide(CO_(2))electroreduction. In this work, this aspect is deeply analyzed by correlating the results of impedance spectroscopy characterization with those obtained by a bubble-induced mass transport modeling under controlled diffusion conditions on a gold rotating disk electrode. The effects of potential and rotation rate on the local environment are also clarified. In particular, it has been found that CO_(2) depletion occurs at high kinetics when the rotation is absent, giving rise to an increment of the competing hydrogen evolution reaction. This feature reflects in an enlargement of the diffusion resistance, which overcomes the charge transport one.

Valorizing carbon dioxide via electrochemical reduction on gas-diffusion electrodes

The electrochemical carbon dioxide(CO_(2))reduction provides a means to upgrade CO_(2)into value-added chemicals.When powered by renewable electric-ity,CO_(2)electroreduction holds the promise of chemical manufacturing with carbon neutrality.A commercially relevant CO_(2)electroreduction process should be highly selective and productive toward desired products,energetically efficient for power conversion,and stable for long-term operation.To achieve these goals,designing gas-diffusion catalytic electrodes and prototyping reactors built upon in-depth understandings of the reaction mechanisms are of para-mount importance.In this review,the fundamentals of gas-diffusion electrodes are briefly presented.Then,the most recent advances in developing high-performance CO_(2)reduction using gas-diffusion electrodes are overviewed.Reactor engineering aiming at enhancing productivity,energy efficiency,CO_(2)single-pass utilization,and operating lifetime is further discussed.Challenges in developing CO_(2)electroreduction systems are included.The prospects for advancing CO_(2)electroreduction toward practical applications are also narrated.

Real-time in situ TEM studying the fading mechanism of tin dioxide nanowire electrodes in lithium ion batteries

Fading mechanism of tin dioxide （SnO2） electrodes in lithium ion batteries has attracted much attentions, which is of great importance for the battery applications. In this paper, electrochemical lithiation-delithiation cycles of individual SnO2 nanowires were conducted in situ in a high-resolution transmission electron microscopy （TEM）. Major changes in volume with expan- sions of 170%~300% on SnO2 nanowire electrodes were observed during the first lithiation process in electrochemical cycling, including conversion reaction of SnO2 precursor to Li20 matrix and active lithium host Sn, and alloying of Sn with Li to form brittle Li-Sn alloy. SnO2 nanowire electrodes were inclined to suffer from thermal runaway condition in the first two cycles. During cycling, morphology and composition evolution of SnO2 nanowire electrodes were recorded. Cyclic lithiation and del- ithiation of the electrode demonstrated the phase transition between Lii3Sn5 and Sn. Metallic Sn clusters were formed and their sizes enlarged with increasing cycle times. Detrimental aggregation of Sn clusters caused pulverization in SnO2 nanowire elec- trodes, which broke the conduction and transport path for electrons and lithium ions. The real-time in situ TEM revealed fading mechanism provides important guidelines for the viable design of the SnO2 nanowire electrodes in lithium ion batteries.

Manganese dioxide(MnO_(2))/Fullerene-C_(60)-Modified Electrodes for the Voltammetric Determination of Rifaximin

Rifaximin(RFX)is a broad-spectrum oral antibiotic with bactericidal actions against Gram-negative and Gram-positive bacteria.In the present work,a sensitive voltammetric assay for the RFX in pharmaceutical formulations is designed using nanostructured working electrodes.Surface functionalization with manganese dioxide(MnO_(2))/fullerene-C_(60) nanocomposite exhibited the highest electrochemical responses with a sharp oxidation peak at about 336 mV that was obtained using the differential pulse voltammetry(DPV).The cyclic voltammetry(CV)and electrochemical impedance spectroscopy(EIS)were applied,while the electrode matrix composition including types of nanomaterials,electroanalytical parameters,and pH eff ect were optimized.To that end,using the DPV,high sensitivity was obtained from the linear calibration curve ranged from 0.8 to 31.5μg·mL^(-1) with the correlation coe fficient of 0.99,limit of detection of 0.76μg·mL^(-1) and limit of quantification of 2.31μg·mL^(-1) .Accordingly,the designed approach is off ering a potential applicability towards the RFX determination in pharmaceutical preparations and its quality control.

面向栽培基质的二氧化钛电极EGFET pH传感器设计

针对农业生产中栽培基质直接在线检测pH准确性差的问题,采用化学腐蚀法,制备出具有氢离子敏感特性和超亲水特性的二氧化钛(TiO_(2))电极,并且采用退火工艺以提高电极表面硬度;将TiO_(2)电极与金属氧化物场效应晶体管(MOSFET)组合成基于延伸式栅极场效应晶体管(EGFET)的pH传感器.测试得到传感器灵敏度为0.05063 V/pH,重复性试验的变异系数最大为0.0057.测试结果表明该传感器具有良好的灵敏度、重复性和稳定性.选取4种典型栽培基质进行pH在线检测应用试验,pH检测误差的绝对值最大为0.18,经过温度补偿后误差的绝对值最大为0.11;使用后电极表面的亲水性依旧保持良好.应用试验结果表明,该传感器适用于栽培基质pH在线检测.

新型电化学反应器降解苯酚废水的研究

以自制钛基PbO_(2)电极为阳极,以碳纤维管为阴极成功开发了一种基于电磁感应无线供电技术的微型电解池填充式电化学反应器,从电解质浓度、pH值和输入电压等等方面探究了新型电化学反应器对苯酚废水的最佳降解条件,当电解质浓度为0.012 5 mol/L,pH值为5,输入电压为8 V时进行降解100 min,苯酚降解率可达92%,处理效果最佳。与传统平板式电化学反应器相比具有明显优势。

铈掺杂量对钛基锡锰铈氧化物涂层电极表面形貌及电化学性能的影响

[目的]电沉积用钛基二氧化锰电极的电化学性能有待提高。[方法]采用热分解法在450℃下制备了以SnO_(2)为中间层,稀土铈掺杂量不同的钛基MnO_(2)电极(Ti/SnO_(2)/MnO_(2)+CeO_(2)),通过场发射扫描电子显微镜与循环伏安测量、电化学阻抗谱、析氧极化曲线测试、加速寿命试验等电化学方法对电极的活性层形貌及电化学行为进行分析。[结果]铈掺杂可以明显改变活性层形貌,使其形成由大量圆形晶粒组成,均匀且致密的表面结构。当铈掺杂量为4%时,电极具有最平整的活性表层,其伏安电荷容量约为未掺杂铈时的6倍,加速寿命约为未掺杂铈时的1.8倍。[结论]适量掺杂铈可以提高钛基二氧化锰涂层电极的电催化活性及延长其使用寿命。

CeO_(2)@Ni(OH)_(2)/CC复合电极材料的制备及其性能的研究

以柔性碳纤维(CC)为基底,采用化学镀法和电化学沉积法负载Ni(OH)_(2),并对其制备条件进行优化,得到性能良好的Ni(OH)_(2)/CC复合材料,再以电化学方法对Ni(OH)_(2)/CC进行稀土掺杂改性,制备出CeO_(2)@Ni(OH)_(2)/CC复合电极材料。采用透射电镜(TEM)、场发射扫描电子显微镜(SEM)、X射线衍射仪(XRD)和X射线光电子能谱分析(XPS)等测试对样品的形貌、组成以及结构进行分析;稳定性测试结果表明电极材料的比电容量呈先上升后稳定的趋势,电容保持率为164.76%;10 mA/cm^(2)的恒电流充放电时,CeO_(2)@Ni(OH)_(2)/CC的比电容高达872 mF/cm^(2)。

3D花状VO_(2)(B)正极材料的制备与电化学性能研究

以五氧化二钒和柠檬酸为原料,采用水热反应法制备了具有大比表面积和优异结构稳定性的3D花状VO_(2)(B)电极材料。采用X射线衍射、扫描电子显微镜、透射电子显微镜等对VO_(2)(B)晶体结构和形貌进行了表征,通过恒流充放电、循环伏安法等对VO_(2)(B)电极材料的电化学性能进行了测试。结果表明:电流密度0.1 A/g下,3D花状VO_(2)(B)电极材料的首次放电比容量达227 mAh/g;1 A/g高电流密度下,初始放电比容量仍达151 mAh/g,300次充放电循环后的容量保持率为79.6%,该电极材料表现出良好的倍率性能。

A Cu-Pd alloy catalyst with partial phase separation for the electrochemical CO_(2) reduction reaction

Cu catalysts can convert CO_(2) through an electrochemical reduction reaction into a variety of useful carbon-based products.However,this capability provides an obstacle to increasing the selectivity for a single product.Herein,we report a simple fabrication method for a Cu-Pd alloy catalyst for use in a membrane electrode assembly(MEA)-based CO_(2) electrolyzer for the electrochemical CO_(2) reduction reaction(ECRR)with high selectivity for CO production.When the composition of the Cu-Pd alloy catalyst was fabricated at 6:4,the selectivity for CO increased and the production of multi-carbon compounds and hydrogen is suppressed.Introducing a Cu-Pd alloy catalyst with 6:4 ratio as the cathode of the MEAbased CO_(2) electrolyzer showed a CO faradaic efficiency of 92.8%at 2.4 V_(cell).We assumed that these results contributed from the crystal planes on the surface of the Cu-Pd alloy.The phases of the Cu-Pd alloy catalyst were partially separated through annealing to fabricate a catalyst with high selectivity for CO at low voltage and C_(2)H_4 at high voltage.The results of CO-stripping testing confirmed that when Cu partially separates from the lattice of the Cu-Pd alloy,the desorption of~*CO is suppressed,suggesting that C-C coupling reaction is favored.

球状废轮胎热解炭/二氧化锰纳米片复合电极材料制备及超电容性能研究

高锰酸钾(KMnO_(4))和废轮胎热解炭(AC)在室温下水溶液中发生共沉淀氧化还原反应,制备了球状废轮胎热解炭/二氧化锰纳米片复合电极材料(AC-MnO_(2)),通过改变AC与KMnO_(4)的反应时间控制纳米复合材料的形态以及二氧化锰(MnO_(2))在AC上的负载量。研究结果表明:在1 moL/L Na 2SO_(4)电解液中,反应时间为1 h制备的样品(AC-MnO_(2)-1)比电容为177.4 F/g(1 A/g)。即使在10 A/g的高电流密度下,经过10000次循环后,AC-MnO_(2)-1的电容保持率也达到99.72%。以此纳米复合材料作为正负电极材料组装了对称超级电容器(SSC),1 A/g时的比电容高达80.3 F/g,能量密度为18.0 Wh/kg,功率密度为899.6 W/kg。