A systematic study on the influence of electrochemical charging conditions on the hydrogen embrittlement behaviour of a pipeline steel

Although hydrogen embrittlement (HE) has been the subject of extensive research over the past century, a systematic study on the HE susceptibility of steels under different electrochemical charging conditions has been lacking. This study specifically targets this knowledge gap by evaluating the HE behaviour of a typical pipeline steel X65 after hydrogen-charging in acidic, neutral, and alkaline electrolytes that simulate various industrial environments. Results from a series of experiments show that the HE susceptibility of X65 steel varied significantly with hydrogen-charging electrolytes and, to a smaller extent, with electrochemical charging variables. The highest and lowest HE susceptibilities were found from specimens charged in acidic and alkaline electrolytes, respectively. An increase in yield strength was observed for almost all hydrogen-charged specimens, regardless of the charging conditions. Under severe electrochemical charging conditions, blistering was detected and mechanical properties were substantially decreased. Discussion has been made in comprehending these relationships.     

The influence of some additives on the electrochemical behaviour of sintered nickel electrodes in alkaline electrolyte

Sintered nickel electrodes containing cobalt and cadmium hydroxides as additives were prepared by anodic polarization in 42 wt.% KOH solution of sintered nickel supports impregnated with mixed metal nitrate solutions. The structural and electrochemical characteristics of these electrodes were investigated by scanning electron microscopy, X-ray diffraction, cyclic voltammetry and charge–discharge curves. The addition of Co(OH)₂ and Cd(OH)₂ in active material have been shown to increase the discharge capacity and coulombic efficiency of nickel electrode by improvement of the electrode processes reversibility and by minimizing of the parasitic oxygen evolution reaction.     

The influence of formation conditions on the electrochemical behavior of lead oxide in sulfuric acid solution

In course of anodic oxidation of lead in chloride-nitrate melt it has been formed β-PbO either in the form of nanopowder with the average size of the particles 20-70 nm or in the form of nanofibers with the thickness of 20 nanometers and length 500 nm. Synthesis is easily reproduced and can become a basis of industrial production lead nano-oxide. Lead oxide nanopowders and nanofibers tested in a course of potentiodynamic cycling in working conditions of a positive electrode of the acid lead battery, have shown good reproducibility of results and high values of currents density that can be unequivocally connected with increase in the true area of a surface of active mass of electrodes.     

Electrical analysis of Li/SOCl2 cell connected with electrochemical capacitor

A Li/SOCl₂ bobbin-type cell, connected in parallel with an electrochemical capacitor, is investigated in order to overcome the voltage delay problem at high-rate discharge. In spite of the high internal resistance of the Li/SOCl₂ cell due to the passivation, the voltage delay is suppressed. Impedance measurements, in which the cell is separated from the capacitor, explain the suppression process clearly. The electrochemical capacitor operates as a high-current buffer and voltage-delay suppressor for the Li/SOCl₂ bobbin-type cell.     

Influence of preparation conditions of spherical nickel hydroxide on its electrochemical properties

The influence of various conditions in spherical nickel hydroxide preparation on its electrochemical properties is studied. Experimental results show that several factors, such as pH and temperature, exert a great influence on the properties of the final product. Optimum conditions and reference data for preparing spherical nickel hydroxide with excellent properties are provided.     

Effect of the preparation conditions on the performance of TiO2 nanotube arrays obtained by electrochemical oxidation

In this paper, nanotubular arrays of TiO₂ are used as anode in an undivided electrochemical cell where the water photosplitting process may occur enhanced by the external applied potential. The behavior of the nanotubular structure, prepared by electrochemical anodization of Ti foils, is investigated. All the samples were submitted to thermal annealing in order to transform the amorphous structure into crystalline. Emphasis is paid on the influence of the current transient during the anodization on the photochemical response of the samples. Depending on the current transient, a different distribution of defects, at the surface or in the bulk, is originated in the initial structure, which resulted differently sensitive to the temperature.     

The factors affecting the electrochemical performance of Li/LixMnO2 solid-state polymer battery

The electrochemical behavior of an all solid-state Li/Li_xMnO₂ polymer cell was evaluated by using three kinds of polymer-electrolytes in the composite positive electrodes. The discharge-rate capability and cycle life was significantly improved by using low-molecular weight polymer-electrolyte. It was confirmed that the improvement is due to the smaller charge transfer resistance between a polymer-electrolyte/cathode material interface, and the compatibility of polymer-electrolyte toward the cathode material is much more direct than the ionic conductivity of the polymer-electrolyte in the effects on its rate capability and cyclability.     

Dynamic behaviour of Li batteries in hydrogen fuel cell power trains

A Li ion polymer battery pack for road vehicles (48 V, 20 Ah) was tested by charging/discharging tests at different current values, in order to evaluate its performance in comparison with a conventional Pb acid battery pack. The comparative analysis was also performed integrating the two storage systems in a hydrogen fuel cell power train for moped applications. The propulsion system comprised a fuel cell generator based on a 2.5 kW polymeric electrolyte membrane (PEM) stack, fuelled with compressed hydrogen, an electric drive of 1.8 kW as nominal power, of the same typology of that installed on commercial electric scooters (brushless electric machine and controlled bidirectional inverter). The power train was characterized making use of a test bench able to simulate the vehicle behaviour and road characteristics on driving cycles with different acceleration/deceleration rates and lengths. The power flows between fuel cell system, electric energy storage system and electric drive during the different cycles were analyzed, evidencing the effect of high battery currents on the vehicle driving range. The use of Li batteries in the fuel cell power train, adopting a range extender configuration, determined a hydrogen consumption lower than the correspondent Pb battery/fuel cell hybrid vehicle, with a major flexibility in the power management.     

Estimation of electrochemical charge storage capability of ZnO/CuO/reduced graphene oxide nanocomposites

Nanocomposites of ZnO/CuO with rGO were synthesized using sonochemical and thermal treatment methods. The formation of ZnO and CuO phases on the rGO sheets and both ZnO/CuO in the ternary component nanocomposites were confirmed from IR spectroscopy and X-ray photoelectron spectroscopy. The microstructure of the nanocomposites as revealed by TEM and FE-SEM suggested that CuO was decorated as nano-rods, whereas ZnO particles retained the spherical shape. In case of ternary nanocomposite, both nano-rods and spherical particles were agglomerated on the rGO sheets. The pseudocapacitive behavior of ZnO-rGO nanocomposite corresponded to relatively higher specific capacitance (344.6 F/g) compared with other nanocomposites. The galvanostatic cyclic charge/discharge (GCD) tests also confirmed that ZnO-rGO nanocomposite could provide the highest specific energy (21.7 Wh/kg) and power density (129.8 kW/kg) at 0.4 A/g compared with CuO-rGO and ZnO/CuO-rGO.     

Thermal and electrochemical behaviour of C/LixCoO2 cell during safety test

Thermal and electrochemical processes in a 1000 mAh lithium-ion pouch cell with a graphite anode and a Li_xCoO₂ cathode during a safety test are examined. In overcharge tests, the forced current shifts the cell voltage to above 4.2 V. This causes a cell charged at the 1 C rate to lose cycleability and a cell charged at the 3 C rate to undergo explosion. In nail penetration and impact tests, a high discharge current passing through the cells gives rise to thermal runaway. These overcharge and high discharge currents promote joule heat within the cells and leads to decomposition and release of oxygen from the de-lithiated Li_xCoO₂ and combustion of carbonaceous materials. X-ray diffraction analysis reveals the presence of Co₃O₄ in the cathode material of a 4.5 V cell heated to 400 °C. The major cathode product formed after the combustion process cells abused by forced current is Co₃O₄ and by discharge current the products are LiCoO₂ and Co₃O₄. The formation of a trace quantity of CoO through the reduction of Co₃O₄ by virtue of the reducing power of the organic solvent is also discussed.     

The electrochemical behaviour of the carbon-coated Ni0.5TiOPO4 electrode material

Ni_0.5TiOPO₄ oxyphosphate exhibits good electrochemical properties as an anode material in lithium ion batteries but suffers from its low conductivity. We present here the electrochemical performances of the synthesized Ni_0.5TiOPO₄/carbon composite by using sucrose as the carbon source. X-ray diffraction study confirms that this phosphate crystallizes in the monoclinic system (S.G. P2₁/c). The use of the Ni_0.5TiOPO₄/C composite in lithium batteries shows enhanced electrochemical performances compared with the uncoated material. Capacities up to 200 mAh g⁻¹ could be reached during cycling of this electrode. Furthermore, an acceptable rate capability was obtained with very low capacity fading even at 0.5C rate. Nevertheless, a considerable irreversible capacity was evidenced during the first discharge. In situ synchrotron X-ray radiation was utilized to study the structural change during the first discharge in order to evidence the origin of this irreversible capacity. Lithium insertion during the first discharge induces an amorphization of the crystal structure of the parent material accompanied by an irreversible formation of a new phase.     

Study of electrochemical process conditions for the electricity production in microbial fuel cell

The aim of this study was to focus on the optimization of various process parameters such as time (days), pH, and electrode type on electricity production by a microbial fuel cell (MFC). The efficiency of MFC was examined based on the current (A) and potential (V) measurements. In MFC, the anode section was filled with 500 mL of rumen fluid, slaughter house waste, and 2 g of hay as substrate. The cathode section was filled with distilled water, which acted as the air cathode. The results obtained confirmed that copper anode explores the maximum efficiency compared to stainless steel and aluminum. The biofilm attached to the electrode is electrochemically active as per the redox potential shown in cyclic voltammogram results.     

The influence of annealing conditions on the efficiency of phosphorous gettering in CZ-Si for solar cell applications

The effect of the annealing ambient on the efficiency of the phosphorous gettering process for Czochralski (CZ) silicon wafers is investigated in this paper. Phosphorous is diffused from a POCl₃ source at different temperatures into single-crystal p-type silicon wafers having a resistivity of around 1 ohm/cm. This is followed by an additional heat treatment in either oxidizing (wet and dry oxide) or in inert (argon) ambient. The laser microwave photoconductivity decay method is used to monitor the changes in the minority carrier lifetime after the phosphorous diffusion and the subsequent annealing. Furthermore, solar cells are fabricated on the treated samples in order to correlate the lifetime measurements with the illuminated I-V characteristics of the cells.     

The compression of hydrogen in an electrochemical cell based on a PE fuel cell design

The compression of gases in conventional compressors is often combined with low efficiency and the contamination of the compressed gases. In this paper, a system is described that uses an electrochemical cell for the compression of hydrogen. This electrochemical hydrogen compressor operates at lower hydrogen flux than mechanical hydrogen compressors. Further development of polymer electrolyte membrane (PEM) fuel cells afford a good prospect of realizing the electrochemical compression on a competitive basis. A specialized gas diffusion layer established the possibility to pressurize the cathode volume up to 54 bar. The ohmic resistance and pressure stability have been rescued by an improved membrane electrode assembly (MEA). A three cell stack on a laboratory scale has been designed. Data of single cell and stack experiments will be discussed in this paper. The advantages of the electrochemical system, apart from the efficiency, are: noiseless operation, purified hydrogen and simplicity of the system cooling.     

The influences of some additives on electrochemical behaviour of nickel electrodes

Nickel hydroxide is used as an active material in positive electrodes of rechargeable alkaline batteries. Since the nickel hydroxide electrode exhibits a poor performance which results not only from the competitive reactions of the oxidation of the active material but also from the evolution of oxygen. Its reduced charge acceptance is suspected to be related to a relatively long distance between nickel hydroxide particles and the nearest portion of the substrate. The practical capacity of the positive nickel electrode depends on the efficiency of the conductive network connecting the Ni(OH)₂ particle with the current collector.     

The influence of the solid/porous electrode interphase on the behaviour of porous lead dioxide electrodes

A method is described by which the ease of reduction and reoxidation of porous lead dioxide electrodes may be assessed in the short time. Fourteen alloAntimony at 6% is far superior to the other electrodes investigated. Bismuth appears to be an enhancing ingredient and it is suggested that evidence fr     

Investigations on the electrochemical behaviour of prussian blue films in acetonitrile

The differences noticed in the order of preference for alkali metal cations through the channels of Prussian blue surface modified electrodes during redox reaction in aqueous versus acetonitrile media are presented. Since intercalation/deintercalation processes by alkali metal cations like K⁺, Na⁺, Li⁺, etc., help in deciding the efficacy of the PB film in device fabrications, the associated columbic charges and diffusion coefficient values computed from chronoamperometric and chronocoulometric studies are reported.     

Effects of preparation conditions on the electrochemical and morphological characteristics of Li4Ti5O12 powders prepared by spray pyrolysis

Li₄Ti₅O₁₂ anode powders were prepared by post-treatment of the precursor powders obtained by spray pyrolysis at various preparation conditions. The precursor powders had fine size, narrow size distribution, dense inner structure and homogeneous composition when the flow rate of the carrier gas and the preparation temperature were 10 l min⁻¹ and 800 °C. The spherical shapes of the precursor powders obtained at the optimum preparation conditions maintained after post-treatment at a temperature of 800 °C. The mean sizes of the Li₄Ti₅O₁₂ powders were controlled by changing the concentrations of the spray solution. The initial discharge capacities and cycle properties of the Li₄Ti₅O₁₂ powders were strongly affected by the preparation temperatures of the precursor powders. The optimum preparation temperature of the precursor powders was 800 °C when the flow rate of the carrier gas was 10 l min⁻¹. The discharge capacities and cycle properties of the Li₄Ti₅O₁₂ powders were not affected by flow rates of the carrier gas. The Li₄Ti₅O₁₂ powders had good cycle properties irrespective of the concentrations of the spray solution. However, the Li₄Ti₅O₁₂ powders obtained from the spray solutions with high concentration above 0.5 M had high discharge capacities than those obtained from the spray solutions with low concentration below 0.1 M.     

The influence of noble-metal-containing cathodes on the electrochemical performance of anode-supported SOFCs

In order to enhance the catalytic activity of the cathode for oxygen reduction and thus to increase the electrochemical performance of planar anode-supported solid oxide fuel cells, Pd, Ag, or Pt was added to the cathode. Four routes were used to add these noble metals: infiltration of the cathode with a Pd solution, deposition of Pt on the electrolyte surface, mixing of La_0.65Sr_0.30MnO₃ (LSM) and YSZ cathode powders with different metal precursors (Pt and Pd black, Pd on activated carbon, Ag powder, Ag₂O, Ag acetate, Ag citrate, Ag₂CO₃, colloidal Ag, AgNO₃), and synthesis of LSM powder with the addition of AgNO₃.

Between 750 and 900 °C no electrocatalytic effect occurred with respect to the presence of Pt, either added by deposition on the electrolyte or by mixing with cathode powders. Infiltration of the cathode with a Pd solution or mixing with Pd black did not result in a positive effect either. A catalytic effect was only found with Pd on activated carbon and in particular at lower temperatures.

Cells prepared with Ag powder and Ag₂O showed an improved electrochemical performance compared to Ag-free cells sintered at the same temperature (920 °C). However, in comparison to Ag-free cells sintered at the standard temperature (1100 °C) lower current densities were measured. This can be explained by a weak contact between electrolyte and cathode functional layer and an insufficiently sintered cathode. A detrimental effect was observed regarding the addition of the other Ag precursors. Thermal decomposition of these precursors resulted in the formation of large pores in the cathode.     

The influence of calcium compounds on the behaviour of the nickel electrode

The nickel hydroxide electrode normally exhibits a poor change-acceptance which results from the competitive reactions of the oxidation of active material and the evolution of oxygen. The combined addition of cobalt and a calcium compound to the nickel hydroxide can improve appreciably the utilization and discharge potential of the active material. The action of the calcium additive is to increase the oxygen evolution potential, while the cobalt imparts good conductivity to the active material for both electrons and protons.