Preparation,characterization and application of alkaline leached CuNiZn ternary coatings for long-term electrolysis in alkaline solution

The NiCuZn ternary coating was electrochemically deposited on a copper electrode. Then, it was etched in a concentrated alkaline solution (30% NaOH) to produce a porous and electrocatalytic surface suitable for use in the hydrogen evolution reaction (HER). The surface composition of coating before and after alkaline leaching was determined by energy dispersive X-ray (EDX) analysis. The surface morphologies were investigated by scanning electron microscopy (SEM). The long-term stability of electrode prepared for alkaline water electrolysis was investigated in 1 M KOH solution with the help of cathodic current-potential curves and electrochemical impedance spectroscopy (EIS) techniques. It was found that, the NiCuZn coating has a compact and porous structure with good physical stability. Alkaline leaching process further improved the activity of NiCuZn coating in comparison with binary NiCu deposit for the HER. The long-term operation at −100 mA cm⁻² showed good electrochemical stability over 120 h.     

Phthalate-derivative/TiO2-modified electrode for electrochromic application

We studied electrochromic properties (EC) of phthalate derivatives (TP), which showed reversible color change from colorless clear to three primary colors by electrochemical reaction, from a viewpoint of color electronic paper. To improve the ability of keeping coloring state under an open circuit, we successfully prepared terephthalate-derivative/TiO₂-modified electrode and evaluated its EC properties. TP film also showed reversible color change from clear to magenta and enabled not only keeping the coloring state longer under open-circuit condition but also good bleaching response under short-circuit condition.     

Bi-doped La1.5Sr0.5Ni0.5Mn0.5O4+δ as an efficient air electrode material for SOEC

Bi-doped La_1.5-xBi_xSr_0.5Ni_0.5Mn_0.5O_4+δ (LBSNM-x, x = 0, 0.05, 0.1, 0.15) was investigated as a potential air electrode for solid oxide electrolysis cell (SOEC). The effect of Bi doping on the structure, electrical conductivity, chemical compatibility with GDC electrolyte, electrochemical performance and thermal expansion coefficients (TECs) were investigated. XRD characterization results show that the solid solution content of Bi is less than or equal to 0.1. XPS characterization results indicate that Bi doping increases the oxygen vacancy content of LBSNM-x air electrode and thus greatly benefits its oxygen evolution reaction. Among the Bi-doped samples, LBSNM-0.1 electrode has the best electrochemical performance with its lowest Rp (polarization resistance) of 0.28 Ω cm² at 800 °C based on LBSNM-0.1/GDC half-cell. LBSNM-0.1 single cell with 70%CO₂ + 30%CO fuel gas feed on the fuel electrode has achieved current density of 811 mA cm⁻² at 800 °C and 1.4 V, a 62.2% increase relative to that of LSNM single cell. In addition, LBSNM-0.1 single cell exhibits excellent stability at 800 °C and 1.3 V with 70%CO₂ + 30%CO feed gas on the fuel electrode. These results prove that Bi-doped LBSNM-0.1 is an efficient air electrode for SOEC.     

Single wall nanohorns as electrocatalyst support for vapour phase high temperature DMFC

The use of single wall nanohorns (SWNH) as electrocatalyst support has proved to increase the performance of polymer electrolyte membrane-based fuel cells. In order to investigate in more detail such behavior, the electrochemical characterization of SWNH based electrodes was performed. The use of SWNH in vapour phase high temperature direct methanol fuel cells (HT-DMFC) was also addressed. Cyclic voltammetry experiments have indicated a higher electrochemical activity towards methanol electro-oxidation and a higher tolerance to carbonaceous species accumulation for a SWNH based electrode than for carbon black and commercial corresponding ones. Carbon black electrode presented a better performance than SWNH one for oxygen reduction reaction at low current densities while, at higher overvoltages, SWNH electrode performed better. The exact role of the improved performance of SWNH based electrodes is yet not clear but may be related to a higher water vapour adsorption or electrode morphology. Vapour phase HT-DMFC operation showed the improved performance of the SWNH electrode in agreement with previous works and with the electrochemical characterization performed during this work; despite the higher ohmic resistance observed in comparison with the carbon black based electrode. Moreover, SWNH based electrode showed improved fuel cell stability during longer operation times.     

Organic electrochromism for a new color electronic paper

We studied electrochemical properties of terephthalate derivatives, which showed reversible color change from clear to three primary colors by electrochemical stimuli, towards paper-like electronic imaging device. To improve the repetitive stability of the electrochromic cell, ferrocene was added to the electrolyte solution as electron donor (counter redox material). Passive-matrix operation (8×8) of electrochromic display (ECD) has been demonstrated. Moreover, a prototype three-layered ECD, which consisted of cyan, magenta and yellow primary-color layers, was also demonstrated to clarify the potential for full-color electronic paper.     

Electrosynthesis of Bi2O3 thin films and their use in electrochemical supercapacitors

Bismuth oxide (Bi₂O₃) thin films are grown on copper substrates at room temperature by electrodeposition from an aqueous alkaline nitrate bath. The usefulness of electrochemically deposited Bi₂O₃ for electrochemical supercapacitors is proposed for the first time. The supercapacitor properties of Bi₂O₃ electrode are studied in aqueous NaOH solution. The Bi₂O₃ electrode exhibits very good electrochemical supercapacitive characteristics as well as stability in aqueous NaOH electrolyte. The effect of electrolyte concentration, scan rate, and number of cycles on the specific capacitance of Bi₂O₃ electrodes has been studied. The highest specific capacitance achieved with the electrodeposited Bi₂O₃ films is 98 F g⁻¹.     

Lithium alloy formation at bismuth thin layer electrode and its kinetics in propylene carbonate electrolyte

The study on the formation of lithium alloying with Bi thin layer electrode and its kinetics was carried out in 1 mol/dm³ LiClO₄/PC electrolyte. In situ XRD and chronopotentiometry results confirmed the formation of LiBi and Li₃Bi alloy phases with the open circuit potentials of 0.830 and 0.805 V, respectively. The formation of Li₃Bi alloy rather than LiBi alloy was found to be responsible for the mechanical degradation of Li–Bi alloy electrode. Lithium diffusion coefficient in LiBi alloy was evaluated to be in the order of 10⁻¹³ cm²/s by ac impedance measurement. This smaller lithium diffusion coefficient in thin layer electrode than that in the common sheet electrode was attributed to the intrinsic properties of the thin layer electrode. Furthermore, a mechanism involving the adsorption process at the electrode surface was proposed for lithium alloying with bismuth.     

Electrochemical fabrication of Ni–Mo nanostars with Pt-like catalytic activity for both electrochemical hydrogen and oxygen evolution reactions

Synthesis of electrocatalysts with excellent performance for hydrogen and oxygen evolution are the main challenges for production of hydrogen by electrochemical water splitting method. Here, Ni–Mo nanostars were created by electrochemical deposition process at different morphologies and their electrocatalytic behavior was studied for hydrogen and oxygen evolution reactions in 1.0 M KOH solution. Increased electrochemically active surface area due to the nanostars formation, improved intrinsic electrocatalytic activity, increased surface wettability, as well as being binder-free during electrode production, resulted in excellent electrocatalytic behavior. For optimized condition, 60 mV and 225 mV overpotential are needed for generating the current density of 10 mA.cm-² in HER and OER process respectively in the alkaline medium. The lower slope of the electrode compared to the other electrodes also indicated that the kinetics of HER on the surface of the electrode was better. Also, there was very little change in the potential during the stability test, indicating the excellent electrocatalytic stability of the synthesized electrode. The present study introduces a rational, cost-effective and binder-free method for the synthesis of high performance electrocatalysts.     

Electrochemical behavior of lead alloys in sulfuric and phosphoric acid electrolyte

The electrochemical behavior of lead, lead–calcium–tin–aluminum and lead–calcium–tin–aluminium–bismuth alloy electrode has been studied in the electrolyte of sulfuric, phosphoric and mixed acid electrolyte. The electrochemical measurements were performed using a cyclic voltammetry technique (CV) with three-electrode system. The results demonstrated that bismuth(III) doped in the lead electrode can increase electrical capacity. The oxidation peak potential of lead alloy electrode in phosphoric acid shifted to the positive compared to that in sulfuric acid. The formation of PbHPO₄ in phosphoric acid and its passivation are responsible for the positive shift of the oxidation.     

Chemically grown, porous, nickel oxide thin-film for electrochemical supercapacitors

A porous nickel oxide film is successfully synthesized by means of a chemical bath deposition technique from an aqueous nickel nitrate solution. The formation of a rock salt NiO structure is confirmed with XRD measurements. The electrochemical supercapacitor properties of the nickel oxide film are examined using cyclic voltammetery (CV), galvanostatic and impedance measurements in two different electrolytes, namely, NaOH and KOH. A specific capacitance of ∼129.5 F g⁻¹ in the NaOH electrolyte and ∼69.8 F g⁻¹ in the KOH electrolyte is obtained from a cyclic voltammetery study. The electrochemical stability of the NiO electrode is observed for 1500 charge-discharge cycles. The capacitative behaviour of the NiO electrode is confirmed from electrochemical impedance measurements.     

Characterization of interphases appearing on LiNi0.5Mn0.5O2 using Li MAS NMR

⁷Li MAS NMR, usually a bulk characterization technique, is used here to analyze the positive electrode/electrolyte interphase. The sharpening of the NMR spectra line shape as the amount of surface species increases shows that the observed signal is clearly the sum of signals due to the distribution of lithium ions in the interphase in terms of distance from the bulk of electrode active material. This technique is then used to compare characteristics of the interphase coming from the contact with LiPF₆-based electrolyte in the case of storage or electrochemical cycling. A clear influence of the change of potential on the interphase configuration and in particular on its intimacy with the bulk of active material is deduced from the change in NMR spectra lineshape. This information is hardly obtained by other characterization technique, making NMR a powerful tool for the study of interphases and passivation layers in lithium batteries materials.     

Electrochemical properties of Ti2Ni hydrogen storage alloy

In this paper, the long cycling behavior, the kinetic and thermodynamic properties of Ti₂Ni alloy used as negative electrode in nickel-metal hydride batteries have been studied by different electrochemical techniques. Several methods, such as, galvanostatic charge and discharge, the constant potential discharge and the potentiodynamic polarization are applied to characterize electrochemically the studied alloy. The studied electrodes are observed before and after electrochemical tests at different temperatures by scanning electron microscopy.The amorphous Ti₂Ni is activated after five cycles and the achieved maximum discharge capacity is about 67 mAh g^?1 at ambient temperature. Despite the low values of the maximum discharge capacity and the cycling stability (17%) and the steep decrease of the discharge capacity after activation, this alloy conserves a good stability lifetime during a long cycling. A good correlation is observed between the evolution of the discharge capacity and those of the redox parameters during a long cycling.The enthalpy change, the entropy change and the activation energy of the formation reaction of the Ti₂Ni metal hydride are evaluated electrochemically. The found values of the enthalpy change, the entropy change and the activation energy are about ?43.3 kJ mol^?1, 51.7 J K^?1 mol^?1 and 34.9 kJ mol^?1, respectively.     

Development of an SFMM/CGO composite electrode with stable electrochemical performance at different oxygen partial pressures

This paper carefully evaluates the electrocatalytic activity of Sr₂FeMo_0.5Mn_0.5O₆ (SFMM) double perovskite as a candidate to substitute the state-of-the-art Ni/YSZ fuel electrode. The electrochemical performance of a 40% SFMM/CGO composite electrode was studied in CO/CO₂ and H₂ with different oxygen partial pressure. Two different cell configurations are prepared at a relatively low temperature of 800 °C to increase the electrochemically active surface area. The cell was supported with a 150 μm 10Sc1CeSZ electrolyte in the first configuration. The cell in the second configuration was made by applying a 400 nm thin 8YSZ layer on 150 μm CGO electrolyte to improve the electrolyte ionic conductivity. Improving catalytic activity with increasing oxygen partial pressure is a key characteristic of the developed electrode. The polarization resistance of about 0.34 and 0.56 Ω cm² at 750 °C in 3%H₂O + H₂ and 60% CO/CO₂ makes this electrode a promising candidate for SOCs application.     

New anode systems for lithium ion cells

Samples of small particle size bismuth and electroplated Ni–Sn alloy were tested as anodes for lithium ion batteries to highlight the effects of volume changes during charge and discharge on the cycling life of the electrodes. Bismuth was used for its relatively “high” potential of Li–Bi alloys formation (0.8–0.6 V) which prevents other components within the electrode from being electrochemically active versus lithium in this potential window. Electrochemical tests have shown that the capacity fade during cycling is largely dependant of the amount of Bi in the electrode. Electroplated Ni–Sn alloys were directly used as anodes and do not need to be reground nor mixed with additives. Different electroplating conditions, leading to different morphology, highlight the leading role of the particle size of the active materials used in the lithium ion cells.     

Methods to increase electrochemical activity of lanthanum nickelate-ferrite electrodes for intermediate and low temperature SOFCs

In this study the methods to increase electrochemical activity and stability of air electrodes based on LaNi_0·6Fe_0·4O_3-δ (LNF) and Сe_0.8Sm_0.2O_1.9 (SDC) with different collector layers has been developed. The influence of the electrode layers’ composition and sintering conditions on the electrode performance in contact with the SDC electrolyte is considered. The polarization resistance of the electrodes with the LNF collector containing a combined Bi–Cu additive is in a range of 0.60–0.67 Ωcm² at 600 °C. Appearance of low-melting liquid phases during the collector formation gives rise to both additional sintering and electrochemical activation of the functional layers. The optimized electrodes exhibit a low degradation (13–15%) preserving a polarization resistance level of 0.15–0.21 Ω cm² at 700 °C after long-term testing for 600 h. To elucidate reasons of the electrode ageing, changes in the electrode performance and microstructure are analyzed using DRT technique and autocorrelation function analysis of SEM images.     

Application of biphenyl additive in electrolyte for liquid state Al-plastic film lithium-ion batteries

In order to investigate the influence of the biphenyl (BH) as a polymerizable electrolyte additive on the properties of Al-plastic film lithium-ion batteries, we examined the electrochemical properties of batteries which containing different amounts of BH. The main analysis tools were overcharge tests, linear sweep voltammetry, cycling tests, rate capability, thermal stability, AC impedance, etc. The results showed that the BH can electrochemically polymerize at the overcharge potential of 4.5–5.5 V to form a layer on the cathode surface, the internal resistance was increased rapidly after the electrode covered with the black electro-polymerization production, and the internal short-circuit was occurred with enough polymerization product, all of these caused to low overcharge current and good overcharge performance, meanwhile, the overcharge performance was increased with the increasing of BH content. However, the cycling performance was deteriorated with an increase in BH content, but not seriously, so the content of additive is ought to be adjusted to practical need in production.     

Electrochemical- and mechanical stability of catalyst layers in anion exchange membrane water electrolysis

Anion exchange membrane (AEM) water electrolysis is considered a promising solution to future cost reduction of electrochemically produced hydrogen. We present an AEM water electrolyzer with CuCoO_x as the anode catalyst and Aemion as membrane and electrode binder. Full cell experiments in pure water and 0.1 M KOH revealed that the optimum binder content depended on the type of electrolyte employed. Online dissolution measurements suggested that Aemion alone was not sufficient to establish an alkaline environment for thermodynamically stabilizing the synthesized CuCoO_x in a neutral electrolyte feed. A feed of base is thus indispensable to ensure the thermodynamic stability of such non-noble catalyst materials. Particle loss and delamination of the catalyst layer during MEA operation could be reduced by employing a heat treatment step after electrode fabrication. This work summarizes possible degradation pathways for low-cost anodes in AEMWE, and mitigation strategies for enhanced system durability and performance.     

Improvement of thermal stability of an organic-aqueous gel electrolyte for bismuth electrodeposition devices

The purpose of this work is to study bismuth deposition/dissolution behavior in an aqueous electrolytic gel media, aiming its application in electrochromism. The gel was made from a polymeric animal protein derivative. This polymer is extremely consistent and it becomes a transparent gel in the 350–850 nm range (visible region). The cross-linking reaction of the gel was made with formaldehyde, targeting to improve the thermal stability of the polymeric matrix without considerable loss of optical properties during electrodeposition. Differential scanning calorimetry and thermo-mechanical analysis were used to verify the transition temperatures of the gel, showing that the cross-linked material can be heated up to 90°C without great changes in their mechanical properties. Voltammetric and chromogenic experiments carried out with the electrochromic device using the gel as electrolyte, were very promising and the electrochemical reversibility of Bi/Bi³⁺ redox couple is not affected by the cross-linking reaction showing a large variation of absorbance values.     

Nanoporous bismuth electrocatalyst with high performance for glucose oxidation application

Although direct glucose fuel cell (DGFC) is widely regarded as one of the most promising energy systems, the low catalytic activity and inferior instability of most anode catalysts during electro-oxidation of glucose has greatly hampered its potential applications. In this work, an efficient and durable anode catalyst of nanoporous bismuth (Bi) for the alkaline electro-oxidation of glucose was proposed just by a simple de-alloying method. The microstructure and catalytic performance of nanoporous bismuth could be finely tuning through actively controlling the composition of precursor Mg–Bi alloy. A three-dimension structure was formed after de-alloying Mg–Bi precursor, giving rise to an increased specific surface area and correspondingly resulting in an enhanced electro-catalytic performance. It has intimated that the optimal nanoporous Bi catalyst with an open, bi-continuous interpenetrating pore-to-ligament structure was constructed based on Mg₆₅Bi₃₅ alloy etching and exhibited an enhanced current density (as high as 8.04 mA/cm²) during alkaline electro-oxidation of glucose, together with the lowest poisoning rate of 5.6 × 10^?3%. The remarkable electrochemical performance of the nanoporous Bi catalyst, coupling with facile dealloying strategy may facilitate design and development of renewable energy device.     

Electrochemical study of lithiated transition metal oxide composite as symmetrical electrode for low temperature ceramic fuel cells

In this work, Lithiated NiCuZnO_x (LNCZO) composite is synthesized and evaluated as a potential symmetrical electrode for ceria-carbonate composite electrolyte based low temperature ceramic fuel cells. Its crystal structures, the hydrogen oxidation/oxygen reduction electrochemical activities and fuel cell performances are systematically examined on the symmetrical cell configuration. Nano crystallite particles in the form of composite are observed for these oxides. The LNCZO shows relatively high catalytic activities for hydrogen oxidation and oxygen reduction reaction according to the electrochemical impedance spectroscopy measurements. A remarkable low oxygen reduction activation energy of 42 kJ mol⁻¹ is obtained on the LNCZO/ceria-carbonate composite, demonstrating excellent electro-catalytic activity. Especially, the catalytic activity can be further improved in the presence of water in the cathode chamber. The results show that the lithiated transition metal oxide composite is a promising symmetrical electrode for ceria-carbonate electrolyte and composite approach might a probable solution to develop super-performance electrodes for reduced temperature ceramic fuel cells.