Ti/SnO_2-MnO_x-RuO_2/MnO_2电极的制备及其析氧、析氯性能

为了改善金属氯化物溶液电解过程中产生的氯气污染问题,采用热分解法制备了以钛为基体、SnO_2-MnO_xRuO_2为中间层、MnO_2为活性层的电极.应用极化曲线法和Tafel曲线分析法测定了电极在25℃、1moL·L^(-1)的H_2SO_4溶液和NaCl溶液中的析氧与析氯电位.在25℃,电流密度为500 A·m^(-2)条件下,用0.5 mol·L^(-1)的H_2SO_4为电解液,测试电极寿命.试验表明:该电极的析氯电位比析氧电位低0.03V,因此,电解过程中会产生部分氧气,减少了氯气的产生量.电极快速寿命测试结果表明,该电极的寿命为8h.

添加剂对Ni(OH)_2电极充放电性能的影响

Mg、Ca、Sr、Ba、Cd、Zn、Co和La等添加剂以化学共沉积的方式添加到镍电极活性物质Ni(OH)2中,XRD显示Ni(OH)2为β型。恒流充放电和循环伏安实验结果表明:添加剂能提高镍电极的充放电性能,其中Sr、Co和La是比较理想的添加剂。它们能明显提高析氧极化,降低析氧速率,增强电极的可逆性,改善电极的充放电性能。

Electrochemical behavior of Pb-Ag-Nd alloy during pulse current polarization in H_2SO_4 solution

The anodic layer and oxygen evolution behavior of Pb-Ag-Nd alloy during pulse current polarization and constant current polarization in 160 g/L H2SO4 solution was comparatively investigated by chronopotentiometry, SEM, XRD, EIS and Tafel techniques. The results show that the anodic layer on Pb-Ag-Nd alloy formed through pulse current polarization is more intact and presents fewer micro-holes than that formed through constant current polarization. This could be attributed to the low current density period, which works as a ‘recovery period＇. During this period, the oxygen evolution reaction is less intense, which benefits the recovery of porous anodic layer. Pb-Ag-Nd anode also shows a lower anodic potential during pulse current polarization, which is in accordance with its smaller charge transfer resistance and smaller Tafel slope coefficient at high over-potential region. The lower anodic potential could be ascribed to the higher concentration of Pb O2 in the anodic layer, which promotes the formation of more reactive sites for the oxygen evolution reaction.

Preparation and electrochemical characterization of activated carbons by chemical-physical activation

A process was proposed based on the combination of chemical and physical activation for the production of activated carbons used as the electrode material for electric double layer capacitor (EDLC). By material characterization and electrochemical methods, the influences of the activitation process on the specific surface area, pore structure and electrochemical properties of the activated carbons were investigated. The results show that specific surface area, the mesopore volume, and the specific capacitance increase with the increase of the mass ratio of KOH to char (m(KOH)/m(char)) and the activation time, respectively. When m(KOH)/m(char) is 4.0, the specific surface area and the mesopore volume reach the maximum values, i.e. 1 960 m2/g and 0.308 4 cm3/g, and the specific capacitance is 120.7 F/g synchronously. Compared with the chemical activation, the activated carbons prepared by chemical-physical activation show a larger mesopore volume, a higher ratio of mesopore and a larger specific capacitance.

Electrochemical properties of powder-pressed Pb-Ag-PbO_(2) anodes

Pb?Ag?PbO2 composite anodes with different mass fractions(1%,2%,3%,4%and 5%)ofβ-PbO2 were prepared by powder-pressed(PP)method.The galvanostatic polarization curves,Tafel curves and anodic polarization curves were tested in sulfuric acid solution.The morphologies and phase compositions of the anodic layers formed after galvanostatic polarization were investigated by using scanning electron microscope(SEM)and X-ray diffractometer(XRD),respectively.The results showed thatβ-PbO2 can improve the electrocatalytic activity of anodic oxide.The anode containing 3%β-PbO2 had the lowest overpotential of oxygen evolution reaction(OER)and the best corrosion resistance.The morphologies of the anode surfaces were gradually transformed from regular crystals to amorphous ones as the content ofβ-PbO2 increased in anodes.

Dynamic model for predicting nitrogen oxide concentration at outlet of selective catalytic reduction denitrification system based on kernel extreme learning machine

To solve the increasing model complexity due to several input variables and large correlations under variable load conditions,a dynamic modeling method combining a kernel extreme learning machine(KELM)and principal component analysis(PCA)was proposed and applied to the prediction of nitrogen oxide(NO_(x))concentration at the outlet of a selective catalytic reduction(SCR)denitrification system.First,PCA is applied to the feature information extraction of input data,and the current and previous sequence values of the extracted information are used as the inputs of the KELM model to reflect the dynamic characteristics of the NO_(x)concentration at the SCR outlet.Then,the model takes the historical data of the NO_(x)concentration at the SCR outlet as the model input to improve its accuracy.Finally,an optimization algorithm is used to determine the optimal parameters of the model.Compared with the Gaussian process regression,long short-term memory,and convolutional neural network models,the prediction errors are reduced by approximately 78.4%,67.6%,and 59.3%,respectively.The results indicate that the proposed dynamic model structure is reliable and can accurately predict NO_(x)concentrations at the outlet of the SCR system.

EXPERIMENT AND RESEARCH ON DEVELOPMENT AND CHARACTERIZATIONS OF ANODIC ALUMINA MEMBR-ANE FOR USE IN HEMODIALYSIS

Objective The correlation between various formative conditions and the pore characterizationsof the anodic alumina membrane is investigated to seek the optimal conditions for the formation of anodic aluminamembrane. Methods High purity aluminum foils are used as the starting materials. The anodization is conduc-ted in three types of electrolytes, 3% sulfuric acid, 5% sulfuric acid and 2. 7% oxalic acid, respectively, with dif-ferent voltages at for 48h. The characterizations of the pore size, the effective porosity and the pore porosity areobserved and determined by scanning electron microscopy. The hydraulic conductances of the membranes are meas-ured to confirm that the pores are open and evaluate the permselectivity of the membranes. Results The experi-mental result shows that the ordered pore arrays are obtained for oxidation under our experimental conditions. Withthe increasing of the voltage, the pore size and pore porosity increased significantly (P <0.05) , while the effectiveporosity decreased significantly (P <0.05) with the same electrolyte. The pore size formed in 3% sulfuric acid or5% sulfuric acid is much smaller than in 2. 7% oxalic acid as an electrolyte. The hydraulic conductance of anodicalumina membrane that formed under our experimental condition is higher than those of the membranes are availablecurrently used in clinical. Conclusion The results suggest that the optimal conditions for the formation of anodicalumina membrane that used in hemodialysis are in 3% or 5% sulfuric acid with 12. 5V to 17. 5V at for 48h.

Analysis of Absorption and Reaction Kinetics in the Oxidation of Organics in Effluents Using a Porous Electrode Ozonator

A novel electrode design for the in situ generation of ozone in the reaction zone of a tubular reactor is described in this work.The ozone generator uses a porous inner electrode tube in the corona discharge assembly,and the ozone generated around the outer periphery of the porous tube diffuses into the tubular reactor and reacts with the contaminants in the fluid that is being treated.A mathematical model that includes absorption and second order reaction in the film is developed to describe ozonation kinetics of a contaminant dye in the tubular reactor.The model describes the experimental data for dye decolorization,oxidation byproducts,dissolved ozone,and ozone gas concentrations well.Model analysis indicates that the fast dye decolorization reaction occurs partly in the liquid film and partly in the bulk fluid.The model can be used in the selection of appropriate gas-liquid contactors for efficient oxidation of contaminants in effluents.

In situ evolution of surface Co_(2)CrO_(4) to CoOOH/CrOOH by electrochemical method:Toward boosting electrocatalytic water oxidation

Developing non‐noble‐metal electrocatalyst with efficient and durable activity is a urgent task for addressing the sluggish reaction kinetics of electrochemical water oxidation.Structural evolution of the electrocatalyst is an important strategy for achieving enhanced performance.Herein,in situ evolution of surface Co_(2)CrO_(4) to CoOOH/CrOOH(CoOOH/CrOOH‐Co_(2)CrO_(4))by an electrochemical method under alkaline conditions was designed for enhancing the electrocatalytic performance of water oxidation.The experiments demonstrated that the synergy between CoOOH/CrOOH and Co_(2)CrO_(4) resulted in a marked increase in the number of active sites and improved the rate of charge transfer,which enhanced the activity for water oxidation.At a geometrical current density of 20 mA cm^(−2),the overpotential of the oxygen evolution reaction was 244 mV and the turnover frequency was 0.536 s^(−1) in 1.0 M NaOH.

Iron-induced 3D nanoporous iron-cobalt oxyhydroxide on carbon cloth as a highly efficient electrode for oxygen evolution reaction

The development of highly efficient and cost-effective electrode materials for catalyzing the oxygen evolution reaction(OER)is crucial for water splitting technology.The increase in the number of active sites by tuning the morphology and structure and the enhancement of the reactivity of active sites by the incorporation of other components are the two main strategies for the enhancement of their catalytic performance.In this study,by combining these two strategies,a unique three-dimensional nanoporous Fe-Co oxyhydroxide layer coated on the carbon cloth(3D-FeCoOOH/CC)was successfully synthesized by in situ electro-oxidation methods,and directly used as a working electrode.The electrode,3D-FeCoOOH/CC,was obtained by the Fe doping process in(NH4)2Fe(SO4)2,followed by continuous in situ electro-oxidization in alkaline medium of“micro go chess piece”arrays on the carbon cloth(MCPAs/CC).Micro characterizations illustrated that the go pieces of MCPAs/CC were completely converted into a thin conformal coating on the carbon cloth fibers.The electrochemical test results showed that the as-synthesized 3D-FeCoOOH/CC exhibited enhanced activity for OER with a low overpotential of 259 mV,at a current density of 10 mA cm^–2,and a small Tafel slope of 34.9 mV dec^–1,as well as superior stability in 1.0 mol L^–1 KOH solution.The extensive analysis revealed that the improved electrochemical surface area,conductivity,Fe-Co bimetallic composition,and the unique 3D porous structure together contributed to the enhanced OER activity of 3D-FeCoOOH/CC.Furthermore,the synthetic strategy applied in this study could be extended to fabricate a series of Co-based electrode materials with the dopant of other transition elements.

A highly-efficient oxygen evolution electrode based on defective nickel-iron layered double hydroxide

Exploring efficient and cost-effective electro- catalysts for oxygen evolution reaction （OER） is critical to water splitting. While nickel-iron layered double hydroxide （NiFe LDH） has been long recognized as a promising non- precious electrocatalyst for OER, its intrinsic activity needs further improvement. Herein, we design a highly-efficient oxygen evolution electrode based on defective NiFe LDH na- noarray. By combing the merits of the modulated electronic structure, more exposed active sites, and the conductive elec- trode, the defective NiFe LDH electrocatalysts show a low onset potential of 1.40 V （vs. RHE）. An overpotential of only 200 mV is required for 10 mA cm-2, which is 48 mV lower than that of pristine NiFe-LDH. Density functional theory plus U （DFT＋U） calculations are further employed for the origin of this OER activity enhancement. We find the introduction of oxygen vacancies leads to a lower valance state of Fe and the narrowed bandgap, which means the electrons tend to be ea- sily excited into the conduction band, resulting in the lowered reaction overpotential and enhanced OER performance.