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Abstract An in-situ electrochemical activation method was developed to activate the carbon fiber paper (CFP) for the highly efficient concentrated HNO 3 reduction. The defects and heteroatoms were introduced onto the surface of carbon fiber resulting in a significant improvement in the reactivity. Furthermore, the surface wettability of electrode was adjusted to enhance the accessibility of the active surface. Owing to these advantages, the activated-CFP electrode exhibits a higher current density (464.1 mA cm−2) for the electroreduction of 4 M HNO 3 compared to the conventional Pt electrodes (75.39 mA cm−2). Based on scanning electron microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy and contact angle analysis, the HNO 3 reduction mechanism on the activated CFP electrode was discussed. High activity as well as excellent electrochemical and chemical stability in the concentrated HNO 3 make the activated-CFP as an effective alternative for noble-metal electrode in the future industrial applications. Graphical abstract Image 1 [ABSTRACT FROM AUTHOR]

Abstract: A commercial sheet of paper based on natural cellulose fibers acting as permeable membrane with thin film metal cathode (Cu) and anode (Al) layers in each face was used to produce paper batteries that could be interconnected in series and rechargeable using water as electrolyte. Their electrical characteristics and the set of electrochemical reactions that support the experimental behavior observed are described in this paper. A series of integrated batteries able to supply a voltage of about 3V and a current ranging from 0.7μA to 25μA in cells with sizes of 1.2cm×3.0cm for a relative humidity in the range of 50–65% were produced in a single sheet of paper, and successfully applied to control the ON/OFF gate state of paper transistors. [Copyright &y& Elsevier]

Highlights: [•] Solution coating of metal oxide layer directly onto carbon paper. [•] Most uniform Metal oxide coating on functionalized carbon paper. [•] Highest electrochemical stability for metal oxide coated functionalized carbon paper. [ABSTRACT FROM AUTHOR]

We present a novel approach for the synthesis of silver nanoparticles capped with oleylamine (AgNPs/OLA) and its application in conductive ink for electroanalytical application. The synthesized OLA capped AgNPs was characterized with TEM, UV-Vis, EDX, FTIR and TGA to confirm the size, composition and surface modification of NPs. In this paper, we report conductive ink printing using a pen to achieve a best conductivity value of 0.11 × 10 5 Scm −1 . A 10 wt% AgNPs nano-ink solution was used for printing conductive electrodes (counter, reference and working) on-to photo paper and sintered at 150 °C for 1 h to achieve metallization. We demonstrated successful application of printed conductive electrodes in cyclic voltammetry (CV) measurement. To ensure the continuity of conductive pattern, we demonstrated the lighting of LED when conductive track was connected to a 9 V battery. This report shows that paper-based flexible electrodes are user-friendly, cost effective and useful for multiple analyses in CV compared to other printed electrodes. [ABSTRACT FROM AUTHOR]

Highlights: [•] Simple, easy-to-use electrochemical paper-based analytical device. [•] The 3D device allows fast filtration and electrochemical detection. [•] The paper-based electrochemical cell was constructed using pencil and paper. [•] The paper based device allows p-nitrophenol detection at the micromolar level. [ABSTRACT FROM AUTHOR]

Abstract: This paper focuses on an understanding of the influence of paper thickness on the electrochemical performances of graphene papers as an anode for lithium ion batteries. Three types of graphene papers, with thickness of ∼1.5, 3 and 10μm, respectively, were fabricated by vacuum-assisted filtration of reduced graphene nanosheets suspended in water. These papers deliver evidently different lithium storage capacities, with thinner papers always outperform thicker ones. The 1.5μm paper gives rise to initial reversible specific capacities (the first 10 cycles) of ∼200mAhg−1 at a current density of 100mAg−1, while the 10μm paper only presents ∼80mAhg−1 at a current density of 50mAg−1. After 100 cycles, a specific capacity of ∼180mAhg−1 is retained for the 1.5μm paper; in contrast, only ∼65mAhg−1 remains for the 10μm paper. The capacity decline with the paper thickness is associated with the dense restacking of graphene nanosheets and a large aspect ratio of the paper. The effective Li+ diffusion distance in graphene paper is mainly controlled by the thickness of the paper, and the diffusion proceeds mainly in in-plane direction, cross plane diffusion is restrained. As such, the effective contact of graphene nanosheets with electrolyte is limited and the efficiency of carbon utilization is very low in the thick papers. [Copyright &y& Elsevier]

Highlights: [•] A microfluidic origami multianalyte electrochemical immunodevice was fabricated. [•] Polyaniline-AuNPs modified paper working electrodes were used as sensor platform. [•] 3DGS were used as matrices to immobilize the redox probes and antibodies. [ABSTRACT FROM AUTHOR]

Abstract: An approach to the analysis of the impedance of porous electrodes proposed by Barcia et al. [Electrochim. Acta 47 (2002) 2109] is reconsidered. It is pointed out that the impedance data are not sufficient to determine pore length (l) pore radius (r) and number of pores (n), since their analysis can only yield two combinations of these geometrical parameters: nr 3/2 and . However, if one of the geometrical parameters l, r or n is known from an independent measurement, the impedance data can provide the information for estimating the others. [Copyright &y& Elsevier]

The mechanism for the deterioration of the lifetime of dye-sensitized solar cell (DSC) is not clear yet, and there is still no effective way to solve the current situation. In this paper, after the DSC device was assembled and lasted for nearly 700 h, the Dyed-NSF/El interface was reconstructed by electrical erasing and the results showed that the photovoltaic performance of the cell could be regenerated. At the same time, electrochemical impedance spectroscopy was used to analyze the changes of internal electron transport and transfer impedance, surface state defects, etc. in the process of degradation and regeneration, and inferred internal causes of cell degradation and regeneration. It was confirmed that the changes in the structure and properties of Dyed-NSF/El interface was the origin of performance degradation. The results of this paper provide a potential technology that could lead to a significant increase in device lifetime and make DSC no longer a disposable cell. [ABSTRACT FROM AUTHOR]

Abstract: The electrochemical removal of bromate ions was performed with BDD electrodes in a two-compartment electrolytic reactor. Bromate ions removal and the production of Br− were observed and determined. The removal of bromate ions occurred at an applied bias potential of −0.45V (vs. SCE). And, the removal rate increased with the applied bias potential. Within 2h, nearly 90% of bromate ions were removed with the applied bias potential of −1.0V (vs. SCE). Effect of pH on bromate ions removal was slight. SO4 2− and Cl− ions inhibit the electrochemical reduction of bromate ions, which can be explained by the competitive adsorption of coexisting anions at the electrode surface with the bromate ions. In comparison, the graphite and carbon paper electrode exhibit low catalytic activities toward reduction removal of bromate ions under the same experimental conditions. A possible reason was proposed. [Copyright &y& Elsevier]

This paper investigates the open circuit voltage (OCV) during the warm-up process of a high temperature proton exchange membrane fuel cell (HT-PEMFC) from 140 °C to the desired temperature of 180 °C, where the temperature increases with time. The heating strategy involves the external heating of the fuel cell with constant heat input rate. The commonly used Nernst equation, to predict the OCV of the fuel cell, is usually used in transient start-up models. Thus, this papers highlights the limitations of using the Nernst equation where the temperature increases transiently with time. A polybenzimidazole-based HTPEM single cell was set up and the OCV was measured under constant heating power supplied by an external source. A parametric study was done by varying the external heating power and the effect on the OCV was observed. The results showed that the OCV reduces non-linearly with respect to temperature, when the fuel cell is subjected to a constant heating power. This behaviour is clearly in contrast with the Nernst equation, which considers the temperature as steady state. For effective comparison, the OCV was also measured under steady state temperatures, showing an almost constant reduction gradient of ∼ −2.3×10 −4 V/°C. However, the behaviour under a constant heating power show curvilinear reduction of the OCV as the temperature increases. In addition, as the external heating power is increased, the degree of curvature of the OCV profile is greater. Thus, the results clearly indicate that the accuracy of using the Nernst equation in transient thermal start-up models can be improved, by considering a non linear behaviour, as shown in this paper. [ABSTRACT FROM AUTHOR]

Platinum (Pt) nanopillars are grown on porous carbon paper at high pressure using plasma dc magnetron sputtering technique to prepare electrodes for application in Proton Exchange Membrane Fuel Cells (PEMFC). The prepared electrodes have low loading of 0.05 mg cm −2 at anode and loadings in the range of 0.05 – 0.20 mg cm −2 at the cathode. Nanopillars grown on carbon paper take active part in electrochemical reactions in fuel cells leading to enhanced performance with a total Platinum (Pt) loading as low as 0.15 mg cm −2 . The Membrane Electrode Assembly (MEA) with Pt loading of 0.05 mg cm −2 and 0.1 mg cm −2 at anode and cathode respectively shows the best performance with a current density of 0.82 A cm −2 at 0.6 V and maximum power density of 0.67 W cm −2 , which is comparable to commercial standard electrodes with total Pt loading of 2 mg cm −2 . [ABSTRACT FROM AUTHOR]

The paper reports the results of simultaneous mechanical and electrochemical investigations on austenitic (18/8) stainless steel in a 2 % solution of sulphuric acid. The measurements were performed using Galvanodynamic Electrochemical Impedance Spectroscopy (GDEIS). Electrochemical analysis of mechanical passive layer cracking and repassivation conditions during a tensile test was carried out. Application of this methodology allowed monitoring of the natural corrosion process without external current (I DC = 0A) nor potential perturbation of the system. The results proved the usefulness of measurements of actual electrochemical systems at zero external current conditions. It was found that a transition to an active state occurred for relatively high strain rates, while the passive layer cracking process did not depend on the strain rate. [ABSTRACT FROM AUTHOR]

Abstract: Aluminum alloys are used widely in automotive and aerospace industries. The demand for weight savings materials of superior mechanical, thermal and electrical properties has focused attention on aluminum metal matrix composites (AMMCs). AMMCs have been applied in areas that can cost-effectively capitalize on improvements in specific stiffness, specific strength, fatigue resistance, wear resistance, and coefficient of thermal expansion. However, AMMCs typically have lower damage tolerance properties than their unreinforced counterparts, and hence the extent of application in primary structures has been limited. In this paper, the corrosion resistance of ALCOA peak-aged Al6092/SiC/17.5p composite has been evaluated by recording of impedance spectra during immersion over one week in an air-exposed 3.5% NaCl. Results confirmed the occurrence of galvanic, crevice, intergranular corrosion and pitting attack due to the inhomogeneous structure of the composite which is the main reason behind enhancing the corrosion susceptibility. This paper formulates a complex hypothesis concerning the corrosion mechanisms of A6092/SiC/17.5p metal matrix composite in chloride containing solution as a function of time. A four-stage corrosion mechanism has been proposed to explain the sequence and the reasons of occurrence of each corrosion form. [Copyright &y& Elsevier]

Abstract: Microfluidic vanadium redox fuel cells are membraneless and catalyst-free fuel cells comprising a microfluidic channel network with two porous carbon electrodes. The anolyte and catholyte for fuel cell operation are V(II) and V(V) in sulfuric acid based aqueous solution. In the present work, the electrochemical characteristics of the vanadium redox reactions are investigated on commonly used porous carbon paper electrodes and compared to a standard solid graphite electrode as baseline. Half-cell electrochemical impedance spectroscopy is applied to measure the overall ohmic resistance and resistivity of the electrodes. Kinetic parameters for both V(II) and V(V) discharging reactions are extracted from Tafel plots and compared for the different electrodes. Cyclic voltammetry techniques reveal that the redox reactions are irreversible and that the magnitudes of peak current density vary significantly for each electrode. The obtained kinetic parameters for the carbon paper are implemented into a numerical simulation and the results show a good agreement with measured polarization curves from operation of a microfluidic vanadium redox fuel cell employing the same material as flow-through porous electrodes. Recommendations for microfluidic fuel cell design and operation are provided based on the measured trends. [Copyright &y& Elsevier]

Abstract: Graphite oxide (GO) paper, obtained by direct filtration of exfoliated GO in water over PTFE membrane filters, was reduced by using hydrazine vapours. The graphene-paper thus obtained was characterized by the combination of different techniques. The electrochemical characterization by cyclic voltammetry, chronoamperometry and chronopotentiometry presents a strong influence of the working conditions: temperature, electrolyte concentration and current on the electrochemical responses, indicating a good ability of the material to sense ambient and working conditions. Electrochemical devices based on graphene are expected to work as dual, and simultaneous, sensing-actuators. [Copyright &y& Elsevier]

Abstract: This paper examines the use of amine-functionalized templates to create nanopatterned metal features. A key aspect of the work is the use of an additive to increase the plating density and enable continuous metallization of nanoscale features. Specifically, MPS (3-mercapto-1-propane sulfonate) was found to increase the plating density of copper on amine-functionalized surfaces by attaching to the surface via the sulfonic acid group, leaving the thiol free to attract palladium ions to the surface. Amine-functionalized nanotemplates were made by selective deposition of PAAm onto surface patterns created by nano-oxidation of OTS-coated silicon substrates. Selective, continuous metallization was observed for MPS-treated nanotemplates. These results demonstrate the successful creation of flexible amine-functionalized nanotemplates, and the enabling influence of MPS for the metallization of nanometer-scale features. In particular, MPS was found to reduce the pattern width for feasible metallization from 500nm to less than 100nm. While the PAAm templates were used in this paper to demonstrate selective metallization, they have the potential for broad application in areas such as selective surface attachment of biomolecules to nanometer-scale surface features. [Copyright &y& Elsevier]

Abstract In this paper, N-doped reduced graphene oxide and MnO 2 nanocomposite (N-RGO/MnO 2) was synthesized via hydrothermal method, which was used to modify the glass carbon electrode (GCE) for electrochemical detection of Hg2+. p -phenylenediamine was used as the nitrogen source and "bridging" molecule between MnO 2 and RGO. The electrochemical sensing performance towards Hg2+ was evaluated by square wave anodic stripping voltammetry method. The presence of N-RGO/MnO 2 nanocomposite has enhanced the electrochemical performance of the GCE toward Hg2+. The N-RGO/MnO 2 nanocomposite modified electrode was found to have a good sensitivity toward Hg2+ and the favorable sensitivity (72.16 μA/μM) and LOD (0.0414 nM) for Hg2+ were achieved under the optimized conditions. Moreover, the modified electrode possessed a good stability and reproducibility. The excellent performance can be attributed to the characteristic nanostructure and N-doping property of the N-RGO/MnO 2 nanocomposite. This electrochemical sensing strategy is expected to enrich the application field of electrochemical determination and does good to the issue of environment pollution analysis. [ABSTRACT FROM AUTHOR]

Abstract In this paper, a novel electrochemical sensing platform has been developed based on the electrodes modified with heteroaromatic molecules decorated with gold nanoparticles (AuNPs). For this purpose, the GC electrodes were first covered with pyridine and phenanthroline rings by using diazonium reduction method. Then, the formation of AuNPs was achieved via the electrochemical reduction of AuCl 4 − ions preadsorbed to the modified GC surfaces. The AuNPs, for comparison, were also prepared on polyphenylene films (PPh) obtained by electrochemical reduction of in situ generated benzenediazonium salts. The existence of the nanoparticles was confirmed by using spectroscopic and electrochemical techniques such as scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and cyclic voltammetry. The results have shown that the homogeneity of particle distribution is strongly dependent on the nature of the organic film. The electrocatalytic capabilities of the resulting composite films were also assessed both in the anodic and cathodic regions for hydrazine hydrate oxidation and nitrobenzene reduction, respectively. It was found that the AuNPs-modified electrodes showed a significant catalytic effect, since metal nanosites on the surfaces offer a good electrical conductivity and large effective surface area. [ABSTRACT FROM AUTHOR]

Abstract Corrosion of carbon steels in a carbon dioxide (CO 2) corrosive environment is an important issue and in some cases the steel surface can be covered by a protective corrosion product film. Research has shown that under certain conditions, once a truly protective film has precipitated on the steel surface, the corrosion rate can decrease by an order of magnitude. Over many years, both quantitative and qualitative research has been carried out to further understand the initiation and growth of the protective film. However, a main limitation is in the correlation of film properties with bulk solution conditions. Research has shown that serious errors in predicting/reasoning can be made by operating with bulk instead of surface water chemistry conditions. This paper uses a pH sensor design to be used for real time surface pH measurement. The study shows a simultaneous electrochemical and surface pH analysis at two varying conditions of pH (pH 6 and pH 6.6) where a characteristic difference in the morphology and hence protectiveness of a corrosion product film is anticipated. [ABSTRACT FROM AUTHOR]

Abstract In this paper the voltammetric behaviour of the anticancer drug irinotecan (CPT-11), its injectable form in the clinical treatment regimen, irinotecan hydrochloride (CPT-11HCl), and its main metabolites (namely SN-38, SN-38G, APC, and NPC), and the natural chemical analogous camptothecin (CPT) were investigated in acetonitrile using a glassy carbon electrode (GCE), in view of developing an analytical protocol for the therapeutic drug monitoring (TDM) of CPT-11 in patients under chemotherapy regimens. Our results showed that all compounds provided rather complex cyclic voltammetric (CV) patterns in both the negative and positive potential regions. The overall results indicated that the processes recorded in the negative potential region at both GCE and Pt electrodes could be hardly exploited for TDM applications, because of the overlapping of the peaks. Instead, in the positive potential region, the oxidation of the piperidine moiety of CPT-11, which was obtained in CPT-11HCl acetonitrile solutions basified with Na 2 B 4 O 7 (synthetic solutions), proved to be useful for irinotecan quantification, as its process at the GCE took place over a potential region essentially free from interference. Preliminary differential pulse voltammetry (DPV) measurements performed in synthetic solutions of CPT-11HCl, over the concentration range 0.2–9 μM, showed a linear dependence between peak current and concentration with a satisfactory correlation coefficient of 0.992. The reproducibility was within 5% from three replicates. Graphical abstract Voltammogram recorded at a GCE in acetonitrile solution containing CPT-11HCl. Image 1 Highlights • The voltammetric features of Irinotecan and its metabolites are rather complex. • The negative potential regions provides strongly overlapping processes at both GCE and Pt electrodes. • The oxidation process of the tertiary amine end of CPT-11 can be used for its detection. [ABSTRACT FROM AUTHOR]

Abstract: This paper conducts a one-dimensional theoretical study on the electrochemical phenomenon in the dual-layer cathode electrode of polymer electrolyte fuel cells (PEFCs) with varying sub-layer thicknesses, and further extends the analysis to a triple-layer configuration. We obtain the explicit solution for a general dual-layer configuration with different layer thicknesses. Distributions of the key quantities such as the local reaction current and electrolyte overpotential are exhibited at different ratios of the ionic conductivities, electrochemical kinetics, and layer thicknesses. Based on the dual-layer approach, we further derive the explicit solutions for a triple-layer electrode. Sub-layer performances are plotted and compared. The results indicate that the layer adjacent to the electrolyte membrane may contribute a major part of the electrode faradic current production. The theoretical analysis presented in this paper can be applied to assist electrode development through complicated multi-layer configuration for cost-effective high performance electrodes. [Copyright &y& Elsevier]

Abstract: The understanding of the very early stage of copper crystal formation kinetics and mechanism is very important for both fundamental and applied aspects. Particularly the quality of the industrial electrolytic copper deposit can be improved and better controlled. In this paper, copper nucleation mechanism is investigated in real refinery electrolytes. The main aim is to study the influence of potential, temperature and copper concentration on potentiostatic reduction of copper ions. The model of electrocrystallization is considered on the basis of the equations describing the nucleation controlled by diffusion towards a disc-shaped ultramicroelectrode. In the present paper the rates of copper nuclei formation are estimated under different applied potential, temperature, copper and levelling agent concentrations. [Copyright &y& Elsevier]

Abstract: Results presented in this paper are first that demonstrate instantaneous impedance changes versus reactivation potential detected by means of dynamic electrochemical impedance spectroscopy (DEIS) technique for AISI 304 stainless steel dissolution process proceeding during intergranular corrosion (IG) in 0.5M SO4 2− +0.01M KSCN solution of different pHs. Application of DEIS method made it possible to evaluate dynamic changes of the examined system''s impedance in conditions of IG. As a result, controlling stage of the overall rate of AISI 304 SS dissolution process was determined. Moreover, the paper proposes an alternative way of assessment of AISI 304 SS dissolution rate during intergranular corrosion based on approximation to theory of iron dissolution in sulfuric acid medium. Simultaneously, on the basis of the DEIS measurements it was possible to obtain information about the degree of sensitization (DOS) of the examined material. Accordingly, performed researches revealed the advantage of the DEIS technique over the electrochemical potentiokinetic reactivation (EPR) tests when investigating intergranular corrosion process. [Copyright &y& Elsevier]

Abstract: In this paper, nickel–cobalt oxides/carbon nanotube (CNT) composites were prepared by adding and thermally decomposing nickel and cobalt nitrates directly onto the surface of carbon nanotube/graphite electrode to form nickel and cobalt oxides. Carbon nanotubes used in this paper were grown directly on graphite substrate by chemical vapor deposition technique. The capacitive behavior of nickel–cobalt oxides/CNT electrode was investigated by cyclic voltammetry and galvanostatic charge–discharge method in 1M KOH aqueous solutions. The results show that nickel–cobalt oxides/CNT composite electrode has excellent charge–discharge cycle stability (0.2% and 3.6% losses of the specific capacitance are found at the 1000th and 2000th charge–discharge cycles, respectively) and good charge–discharge properties at high currrent density. Additionally, the effect of Ni/Co molar ratio on specific capacitance of the composite electrode was investigated and the highest specific capacitance (569Fg−1 at 10mAcm−2) is obtained at Ni/Co molar ratio=1:1. [Copyright &y& Elsevier]

Abstract: This paper deals with the electrochemical reactivity of boron doped diamond (BDD) electrodes. A comparative study has been carried out to show the influence of the presence of graphitic micro-domains upon the surface of these films. Those graphitic domains are sometimes present on as-grown boron doped diamond electrodes. The effect of doping a pure Csp3 diamond electrode is established by highly oriented pyrolytic graphite (HOPG) abrasion onto the diamond surface. In order to establish the effect of doping on a pure Csp3 diamond electrode, the amount of graphitic domains was increased by means of HOPG crystals grafted onto the BDD surface. Indeed that method allows the enrichment of the Csp2 contribution of the electrode. The presence of graphitic domains can be correlatively associated with the presence of kinetically active redox sites. The electrochemical reactivity of boron doped diamond electrodes shows a distribution of kinetic constants on the whole surface of the electrode corresponding to different active sites. In this paper, we have studied by cyclic voltammetry and electrochemical impedance spectroscopy the kinetics parameters of the ferri/ferrocyanide redox couple in KCl electrolyte. A method is proposed to diagnose the presence of graphitic domains on diamond electrodes, and an electrochemical “pulse cleaning” procedure is proposed to remove them. [Copyright &y& Elsevier]

Abstract: In order to investigate non-linear and non-stationary electrochemical systems, this series of two papers describes a new measurement method for electrochemical impedance spectroscopy (EIS), using specially designed broadband excitation signals. During one single experiment, the impedance, the level of the disturbing noise, the level of the non-linear distortions, and the level of the non-stationary behaviour are simultaneously measured. Part I of the paper presents the measurement strategy and validates it on a linear and a non-linear electrical circuit. In part II the described measurement strategy is applied to the pitting corrosion of aluminium (99.5 wt.%) immersed in an aerated sodium chloride solution. [Copyright &y& Elsevier]

Abstract The preparation of hydrogen by electrochemical water splitting consists of two processes, i.e., hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). It takes scientists a great deal of effort to design and synthesize electrocatalytic materials with high catalytic properties, low fabrication cost and simple synthesis method. In this paper we report the synthesis of the octahedral Co 3 O 4 particles by a simple hydrothermal method, with the double-layer capacitance (C dl) 154.85 mF cm−2, and a lot of {111} high-index facets exposed. The Co 3 O 4 of this structure not only contains oxygen vacancies and hydroxyl groups on the surface, but has a high electrochemical surface area. The synergistic effect of these features makes it a high efficiency catalyst for HER and OER. The bright performance is manifested in that the HER in an alkaline medium requires only 77.9 mV overpotential for a current density of 10 mA cm−2, and the OER needs 301.2 mV overpotential for a current density of 10 mA cm−2, while during the electrolytic overall water splitting, it just needs 1.60 V for a current density of 10 mA cm−2. The durability test also shows good performance of the material both for the HER and OER processes with the tolerating time of Chronoamperometry (j-t) curve test for 20 h. This work not only proves the efficient catalytic performance of this material, but also has the guiding significance for the large volume synthesis of electric catalysts used in industry. Graphical abstract The synthesized Co 3 O 4 particles of octahedral structure show excellent activity for HER and OER in alkaline solutions. And the Faradic efficiency is nearly 100% in alkaline solution. Image 1 [ABSTRACT FROM AUTHOR]

Abstract In this paper, we report on the synthesis and function of self-humidifying nature of manganese oxide supported platinum (Pt/Mn x O x) electrocatalyst under dry gas condition in proton exchange membrane fuel cells (PEMFC) with excellent electrochemical stability, long-term durability and remarkable fuel cell performance. The high-surface area nano-petal shaped manganese oxide (Mn x O x) clusters are synthesized by anodic deposition and the Platinum (Pt) nanoparticles are electrodeposited on diffusion layer (GDL) having two-layers of Mn x O x coating. The morphology and self-humidifying nature of Pt/Mn x O x were extensively studied through HR-SEM, HR-TEM, XPS, XRD, and water uptake studies. The electrochemical stability and long-term durability were investigated through cyclic voltammetry (CV) studies and single cell fuel cell performance. The MEAs using the spherical clusters of clump-like Pt/Mn x O x exhibited a peak power of 0.65 W/cm2 at 0.48 V under dry gas condition without humidification. Also, the fuel cell delivered stable power output at a constant current density of 0.8 A/cm2 for about 150 h with a negligible potential drop of 26 μV h−1. The long-term durability, excellent electrochemical activity and self-humidifying nature of Pt/Mn x O x may be attributed to the formation of hydroxyl groups on Pt/Mn x O x which facilitates the proton conductivity. [ABSTRACT FROM AUTHOR]

In this paper, we explore the successful hydrothermal approach to make Co 3 (PO 4 ) 2 ·4H 2 O/GF micro-flakes composite material. The unique sheet-like structure of the graphene foam (GF) significantly improved the conductivity of the pristine Co-based material, which is a key limitation in supercapacitors application. The composite electrode material exhibited superior capacitive conduct in 6 M KOH aqueous electrolyte in a 3-electrode set-up as compared to the pristine cobalt phosphate material. The material was subsequently adopted as a cathode in an asymmetric cell configuration with carbonization of Fe cations adsorbed onto polyaniline (PANI) (C-Fe/PANI), as the anode. The Co 3 (PO 4 ) 2 ·4H 2 O/GF//C-FP hybrid device showed outstanding long life cycling stability of approximately 99% without degradation up to 10000 cycles. A specific energy density as high as 24 W h kg −1 , with a corresponding power density of 468 W kg −1 was achieved for the device. The results demonstrated the efficient utilization of the faradic-type Co 3 (PO 4 ) 2 ·4H 2 O/GF composite along with a functionalized carbonaceous electric double layer (EDL)-type material to produce a hybrid device with promising features suitable for energy storage applications. [ABSTRACT FROM AUTHOR]

Silicon has been considered as one of the next generation high capacity anode materials. However, dissolution of cathode material in electrolyte, which is a general problem for lithium-ion batteries, hinders the industrial development of silicon anode. This paper designs electrochemical environment of Mn (II) dissolution to study the capacity fading of silicon anode. Electrochemical analysis and differential scanning calorimetry analysis reveals that Mn (II) will decrease the stability of solid electrolyte interphase, leading to acceleration of solid electrolyte interphase excessive growth and decreasing Columbic efficiency of anode. [ABSTRACT FROM AUTHOR]

This paper reported an oxygen vacancy contained SnO 2 -graphene nanocomposite (OVs-SnO 2 -Gr), which was prepared by annealing SnO 2 -graphene nanocomposite in 3 vol% H 2 /Ar atmospheres. It demonstrated with a high reversible capacity of around 510 mAh g −1 after 300 cycles at a current density of 40 mA g −1 , and an impressive reversible rate performance of 391 mAh g −1 can be obtained even at a high current density of 1200 mA g −1 when applied as anode for sodium storage. Evidenced by a new phase of Na 2 SnO 3 during sodium storage reactions, it is found that sodium can insert into crystal lattice of oxygen vacancy contained SnO 2 . Moreover, sodium insertion could arouse a novel structural reconstruction and introduce amorphous phase SnO 2 , which promotes the surface-controlled reaction process and Na + diffusion rates, and enables a good rate performance. Additionally, the H 2 /Ar annealing process increases overall conductivity of electrodes, which further reduces the barrier of Na + diffusion. It is believe that the as-prepared OVs-SnO 2 -Gr is a promising anodes for Na-ion batteries with outstanding electrochemical performance. [ABSTRACT FROM AUTHOR]

This paper focuses on the gradual performance and durability degradation behaviors of a direct methanol fuel cell (DMFC) with more than 3000 h lifetime. This work adopted a new DMFC test strategy and the entire lifetime test consisted of No.1-No.166 single operation. Stage-failure phenomenon occurred in the lifetime test, which indicated the existence of recoverable and non-recoverable degradations during the entire operation process. In-situ electrochemical tests were applied to the DMFC to analyse causes of durability and performance loss. When single cell came to failure, some recoverable methods were conducted to realize the recovery and improvement of DMFC performance and durability. As a result, during each single operation, continuous lifting pressure operation can realize the improvement of catalyst activity and optimization of mass transfer channel. Proton (H + ) recovery method and increasing operation temperature can effectively solve the problem of internal resistance enlargement. According to the results of electrochemical monitoring, higher temperature results in the rapid degradation of catalytic layer activity, and lower temperature causes the increase of membrane resistance. N 2 purging works as an effective method to eliminate the concentration polarization caused by cathode “water flooding” phenomenon. Based on these results, it can be concluded that the main degradation of DMFC successively changes with operation time, which mainly comes from internal resistance enlargement, cathode concentration polarization and final deactivation of catalyst at different operation stages. This work well explains the real long-term degradation behaviors of DMFC along with operation time, and provides several practicable methods for recovering DMFC performance and durability. [ABSTRACT FROM AUTHOR]

Li metal batteries have attracted many attentions owing to their excellent nature, including easier processes and higher energy density than that of conventional Li-ion batteries. However, lithium whiskers often result in the instability of Li anode and electrolyte, and even short circuit, which hinders the safe application of lithium batteries. In this paper, N,N-dimethylethanolamine (DMEA) is employed as a short-chain bifunctional organic additive to save the above problem in Li||LiCoO 2 batteries. DMEA not only effectively restrains the growth of Li whiskers by hydroxyl groups and decreases the concentration of free HF by amine groups, but also forms new high ionic-conductivity DMEA-Li based SEI film rather than only hard LiF SEI layer. As a result, the rate performance and capacity of Li||LiCoO 2 batteries have been remarkably improved, owing to the participation of bifunctional DMEA. The capacity of 159 mA h g −1 has been retained after 150 cycles with a low capacity fading of 0.07 mA h g −1 per cycle, 43% higher than that of DMEA-free cells at 0.5 C . [ABSTRACT FROM AUTHOR]

In this paper, we describe a novel electroanalytical approach that utilizes preconcentration of Escherichia coli ( E. coli) bacteria by electrokinetic phenomena (dielectrophoresis and electrothermal fluid flow), which are generated in an electrolyte solution by a high frequency alternating current (ac) waveform. The bacteria are decorated with silver nanoparticles, so it becomes possible to detect individual bacterial cells one by one, i.e., perform electrochemical counting, due to silver oxidation on a working microelectrode (UME) biased at an appropriate dc potential. We demonstrate that the developed methodology allows for detection of E. coli concentrations two orders of magnitude smaller than what one could detect based on the transfer of E. coli by diffusion only (Sepunaru et al., Biomater. Sci., 3 (2015) 816–820). [ABSTRACT FROM AUTHOR]

In this work, the study of the time-dependent behaviour of lithium carbonate based inhibitor technology for the active corrosion protection of aluminium alloy 2024-T3 is presented. Odd random phase electrochemical impedance spectroscopy (ORP-EIS) is selected as the electrochemical tool to study the corrosion protective properties of a model organic coating with and without lithium carbonate as a function of immersion time, by examination of the non-linearities and non-stationarities in the system. A dedicated qualitative and quantitative analysis allows linking the presence of non-stationarities in a certain frequency range with the (un)stable behaviour of different electrochemical processes. Monitoring of the system with and without lithium corrosion inhibitors during the first 12 h after immersion in a 0.05 M NaCl aqueous solution and modelling the ORP-EIS data with equivalent electrical circuit (EEC) models revealed a relation between the trends in the parameter evolution and the (un)stable behaviour of the morphological changes taking place. This paper shows that the ORP-EIS based methodology allows us to study the behaviour of corrosion inhibitors in an alternative way; the time-dependent behaviour of corrosion inhibitor containing electrochemical systems is highlighted, proving that this a useful approach for further corrosion inhibitor and active protective coating research. [ABSTRACT FROM AUTHOR]

One-step electrochemical synthesis of polypyrrole-vanadium oxide (PPy-VOx) composites was performed on the Vanadium-intercalated pencil graphite (PG) surface in an acetonitrile solution with the presence of carboxymethyl cellulose (CMC). Both intercalated surface and composite coating were characterized using SEM-EDX Spectroscopy and X-Ray Diffraction (XRD) techniques. The capacitive properties of the coating were elaborated in an H 2 SO 4 /water medium using galvanostatic charge–discharge, potential cycling, and electrochemical impedance spectroscopy methods in comparison with the coatings prepared without additives. While V-intercalation provides a significant increase in the specific capacitance, the carboxymethyl cellulose enhances the cyclic performance of the composite. The improvement at the capacitance of the composite may be due to the homogenous distribution as well as the synergetic effect between PPy and VO x . The capacitive properties were studied in aqueous solutions of H 2 SO 4 and Li 2 SO 4 , and in an acetonitrile solution of HBF 4 /TBABF 4 . The specific capacitance value of the composite coating on the V-intercalated pencil graphite was determined as 204 F g −1 in an acetonitrile solution of HBF 4 /TBABF 4 for a mass loading of 10.0 mg cm −2  at 2.0 A g −1 , when the capacitance of bare graphite was subtracted. The two-electrode supercapacitors composed of both asymmetric and symmetric configurations were also prepared and examined in an acetonitrile/adiponitrile solution of HBF 4 /TBABF 4 . The charge–discharge results for asymmetric supercapacitor reveal that the PPy-VO x -CMC composite coating (20 mg cm −2 ) on V-intercalated graphite paper represents a high energy density of 18 Wh.kg −1 and a high power density of 0.43 kW kg -1  at 0.5 A g −1 , as well as a stable cycle life at the potential range of 1.2 V. [ABSTRACT FROM AUTHOR]

In this paper, a special emphasis is given to the newly obtained electrochemical properties at room temperature of the two-dimensional ε′- and γ′-V 2 O 5 polymorphs as sodium intercalation compounds. The structural peculiarities and electrochemical properties of each phase are presented. A full electrochemical and structural reversibility is demonstrated for both compounds upon sodium insertion at high voltage of 2.8 V. This noticeable voltage enhancement (+1 V) compared to α-V 2 O 5 cathode is ascribed to the specific layers organization consisting of bilayered and puckered sheets in ε′-V 2 O 5 and γ′-V 2 O 5 , respectively. Promising data, with large capacities (from 120 to 200 mAh g −1 ) and an excellent cycle life allow to identify new high performance V 2 O 5 - forms as positive electrode materials for sodium-ion batteries. [ABSTRACT FROM AUTHOR]

The paper describes a sensor for single-stranded DNA (ssDNA) biomarker based on anharmonic acoustic signals arising during hybridization with complementary thiolated ssDNA functionalised on the gold electrode of an electrochemical quartz crystal resonator. The steps of sensor preparation and hybridization are carried out in an electrochemical microfluidic flowcell. While the electrochemical impedance spectroscopy does not allow a definitive interpretation, the changes in resonance frequency and third Fourier harmonic current of the resonator on actuation at the fundamental mode indicate formation of a flexibly bound layer. The functionalization and hybridization steps monitored by the anharmonic detection technique (ADT) are described with a simple model based on Duffing nonlinear equation. [ABSTRACT FROM AUTHOR]

The rotating disc electrode (RDE) is by far the most popular of the hydrodynamic electrodes, in which the transport of electroactive species is enhanced by a controlled flow; one of the reasons of this success is its resilience, as the rate of transport of actual RDEs are close to the theoretical predictions. However, if this is true for defect-free electrodes, little is known about the effect of defects on the transport properties of actual RDEs. In this paper, we use state-of-the-art finite volumes computational fluid dynamics simulations to investigate the transport properties of a defect-free cylindrical RDE, and of three RDEs presenting defects that commonly arise from imperfect construction, handling or even just ageing. We show that, while the transport toward the defect-free cylindrical RDE can be considered homogeneous, this is not the case for the other electrodes. We found that the presence of defects has only a minor effect on the average rate of mass-transport of the electrodes, which is what matters for analytical purposes, but that they significantly increase the heterogeneity of mass transport. This heterogeneity can have a significant impact in the context of kinetic studies, especially those in which the response is non-linear with respect to the concentration, like the study of immobilized enzymes using protein film voltammetry. [ABSTRACT FROM AUTHOR]

Understanding the influence of synthesis parameters on morphology and electrochemical properties of carbon nanostructure is necessary for the development of application-tailored materials. We report on the synthesis by plasma enhanced chemical vapor deposition, morphology and catalytic activity towards oxygen reduction reaction (ORR) of hierarchical carbon nanowalls (hCNW) at different deposition times. hCNW are an advancement of common CNW possessing an increased surface area while retaining the ideal mass transport characteristics of common CNW. The hCNW structure results from a synthesis using p -xylene as an aromatic precursor. hCNW are non-doped and metal-free with easily accessible graphitic edge sites at the top of the walls and numerous defects sites located within the porous side walls, which are ideal sites for adsorption and electron transfer. hCNW reveal a high amount of different electrochemically active sites that dominate the material character depending on the deposition time. The hCNW exhibit excellent catalytic activity towards ORR with very high ORR onset potential of 830 mV vs RHE in 0.1 mol L −1 KOH solution and selectivity towards a two electron transfer mechanism. Thereby, the onset is higher than that of several nitrogen doped carbons and one of the highest for pure carbon electrodes. In contrast to other pure carbon materials with similar onsets, oxygen doping of hCNW before the experiments could be ruled out. As such, the results of this paper indicate the existence of inner sphere ORR on sp 2 -carbon. Additionally, the results emphasize the relevance of often overlooked material properties such as surface accessibility as well as electrical conductivity for ORR. [ABSTRACT FROM AUTHOR]

Organic Electrochemical Transistors (OECTs) are emerging devices that find applications as sensors because they offer amazing features such as intrinsic signal amplification, low energy consumption, low cost and easy adaptability to new and unconventional architectures. The signal transduction usually exploits a redox reaction as happens in a common amperometric sensor, but the channel of the transistor is able to amplify this signal. This paper aims to thoroughly investigate the amplification of Faradaic currents in OECT sensors that exploit PEDOT:PSS (poly(3,4-ethylenedioxythiophene):poly (styrene sulfonate)) as semiconductor material in the channel and electrochemical transducer. The devices were fabricated with different geometries and thicknesses of PEDOT:PSS in order to find the best configuration. The amplification was studied in phosphate buffer solution as electrolyte by determining the OECT transconductance. A thick PEDOT:PSS layer and a high ratio between gate and channel areas ensure the best performance from an electrical point of view. The amplification was also studied while the OECTs work as chemical sensors for the detection of ascorbic acid. The highest gain was observed for the thickest PEDOT:PSS channel and the lowest ratio between the gate and the channel areas. Moreover, the gate voltage has an important effect on the transistor amplification, being the gain highest (of about 2 orders of magnitude) for the lowest gate voltage. [ABSTRACT FROM AUTHOR]

This paper presents a comparison between five flow field patterns including parallel, single path serpentine (1-path), dual path serpentine (2-path), triple path serpentine (3-path) and quadruple path serpentine (4-path) with 25 cm 2 active area to identify the pattern with the best performance in terms of distribution of molar fraction of produced hydrogen, current density, temperature and pressure drop. This is a three-dimensional (3-D) numerical analysis for different flow fields based on finite volume method at steady state, single phase and non-isothermal conditions. The results of the numerical analysis are in good agreement with experimental data. The results reveal that serpentine flow field provides better distribution of current density and temperature in comparison with parallel configuration. At voltage of 1.6 V, the current density for 1-path, 2-path, 3-path, and 4-path patterns are almost 0.28, 0.19, 0.13, and 0.10 A/cm 2 higher than parallel pattern, respectively. Also, for 1-path, 2-path, 3-path, and 4-path patterns, the hydrogen mole fraction at outlet of anode channel are 0.0034, 0.0028, 0.0023 and 0.0021, respectively. The results indicate that the 2-path pattern is relatively advantageous in terms of pressure drop, distribution of current density and hydrogen molar fraction. [ABSTRACT FROM AUTHOR]

This paper investigates the influence of the cell compression of a PEM water electrolysis cell. A small single cell is therefore electrochemically analyzed by means of polarization behavior and impedance spectroscopy throughout a range of currents (0.01 A cm −2 to 2.0 A cm −2 ) at two temperatures ( 60 ° C and 80 ° C ) and eight compressions (0.77 MPa–3.45 MPa). Additionally, a computational model is utilized to support the analysis. The main findings are that cell compression has a positive effect on overall cell performance due to decreased contact resistances, but is subject to optimization. In this case, no signs of severe mass transport problems due to crushed transport layers are visible in either polarization curves or impedance plots, even at high currents. However, a Tafel plot analysis revealed more than one slope throughout the current range. The change in the Tafel slope is therefore discussed and connected to the electrochemical reaction or an ohmic contribution from a non-electrode component. [ABSTRACT FROM AUTHOR]

Symmetrical solid oxide fuel cells (SSOFCs) show many advantageous features of simplifying fabrication process, minimizing interdiffusion between components and enhancing coking and sulfur tolerance by operating the anode as the cathode. In this paper, the double-perovskite Sr 2 TiFe 0.9 Mo 0.1 O 6– δ (STFM01) and Sr 2 TiFe 0.8 Mo 0.2 O 6– δ (STFM02) oxides are synthesized by the traditional solid-state reaction and assessed as symmetrical electrodes. Both of the two materials show cubic double perovskite structure with outstanding structural stability, well chemical compatibility and matched thermal expansion coefficients with the common electrolytes in oxidizing and reducing atmospheres under SOFC operating temperatures. From the electrochemical performance, the electrolyte-supported single cell with STFM01 electrode presents the maximum power densities of 573 mW cm −2 in H 2 and 361 mW cm −2 in complex hydrocarbon fuels containing H 2 S at 850 °C, respectively. The electrochemical stability test exhibits that the STFM01 sample showed no any degradation in H 2 and acceptable degradation in hydrocarbon fuels, and STFM02 sample showed no any deterioration during 30-h test in hydrocarbon fuels, which implies that the STFM01 and STFM02 materials had remarkable ability of resisting carbon deposition and sulfur poisoning than the traditional anode material. The efficient and relatively stable double perovskite symmetrical electrodes are much more promising candidate materials for SSOFCs and are beneficial for realizing commercialization of SOFC. [ABSTRACT FROM AUTHOR]

In this paper, a lithium-ion full battery based on a high quality graphitized graphene anode and a high capacity, high rate Li[Ni 0.6 Co 0.2 Mn 0.2 ]O 2 cathode was reported. After carefully designing the cell and improving the initial Coulombic efficiency of the anode, electrochemical performances such as cycling life (500 stable cycles at 1C rate), rate capability(a capacity of 115 mAh g −1 at 10C) and energy density(about 180 Wh kg −1 at 1C rate and a moderate operating voltage) can be achieved, making the battery very promising for powering hybrid electrical vehicles (HEVs) or electric vehicles (EVs). [ABSTRACT FROM AUTHOR]

Understanding properly electrochemical nucleation and growth phenomena is crucial for a wide range of highly active research and technological fields. In this paper, we use a Finite Element Method to solve a Time Dependent Multi-ion Transport and Reaction Model (FEM-TD-MITReM) to report on the growth of an isolated nucleus. This approach takes into account the transport driven by diffusion and migration of all species in the electrolyte together with the electrochemical reactions at the electrode boundary. The numerical results show that, a nucleus which is smaller than a critical size, even after the application of a sufficiently large overpotential, always starts to grow under kinetic control. In later stages, a transition from kinetic to mixed and to diffusion control takes place. The corresponding transition times between growth regimes have been identified and are found to be inversely proportional to the concentration of active species and to decrease exponentially with overpotential and linearly with the initial nucleus size. Both effects are more pronounced in the transition from kinetic to mixed control. Interestingly, under the conditions used for the current simulations, typical from experimental nucleation and growth studies, a few seconds are needed to achieve diffusion control. This implies that, although experiments under similar conditions are normally described by growth under diffusion control, such theory is only valid for sufficiently large active surface. As a consequence, kinetic and mixed control regimes cannot be neglected for a proper interpretation of electrochemical nucleation and growth phenomena. These findings provide a significant benchmark for correctly describing, modelling and interpreting the early stages of electrochemical growth without making assumptions on the diffusional or kinetic limitations. [ABSTRACT FROM AUTHOR]

This paper reports the facile synthesis of a novel architectural of NiS/PEDOT:PSS with DEG, where the complementary features of the three components (well-defined NiS black pepper like nanoparticles on nickel foam, an ultrathin layers of poly (3,4-ethylenedioxythiophene)/poly(styrenesulfonate) (PEDOT:PSS), and diethylene glycol (DEG)) are deposited sequentially to a single entity to fabricate a high-performance electrode for supercapacitor applications. Owing to the high electrical conductivity of the well-defined NiS nanoparticles, in which the conductivity, and good chemical and electrochemical stability is enhanced further by the PEDOT:PSS and DEG thin layers, the as-fabricated NiS/PEDOT:PSS with a DEG chrysanthemum petal-like nanostructure exhibits good rate capability, excellent cycling stability, and high specific capacitance. The PEDOT:PSS with DEG offers extra conductive paths for each layer on NiS, yielding a lower internal resistance and charge-transfer resistance than that of the NiS/PEDOT:PSS without DEG. As a result, the NiS/PEDOT:PSS with the DEG electrode shows a tremendous pseudocapacitance of 750.64 F g −1 at 1.11 A g −1 , along with a high energy density of 24.52 Wh kg −1 at a power density of 138.88 W kg −1 and good cycling stability, suggesting that it is a promising candidate for energy storage. The unique performance of NiS/PEDOT:PSS with a DEG benefits from its unique chrysanthemum petal-like nanostructure, which could offer faster ion and electron transfer ability, greater reaction surface area and good structural stability. [ABSTRACT FROM AUTHOR]

This paper investigates the methodology for differentiation of multistep process of pitting corrosion of AISI 304 stainless steel in the environment of iron (III) chloride. Measurements were performed using Galvanodynamic Electrochemical Impedance Spectroscopy (GDEIS). Application of this methodology allowed monitoring of natural corrosion process without external current ( I DC = 0A ) nor potential perturbation of the system. Applied sinusoidal AC current does not influence significantly registered DC potential. Analysis confirms that it is possible to distinguish all stages of pitting corrosion: passive state, metastable state, initiation of pitting, active pitting corrosion state. Characteristic potential oscillations related with pitting corrosion were detected. Research shows that GDEIS method can be with success utilized in the monitoring of pitting corrosion. [ABSTRACT FROM AUTHOR]

Lithium rechargeable batteries have been used for lithium extraction in recent years. Here, we report on a highly selective lithium recovery system that consists of a LiMn 2 O 4 positive electrode, a Li 1-x Mn 2 O 4 negative electrode and a monovalent selective anion-exchange membrane. The effect of potential, temperature and coexisting ions on lithium extraction were investigated in this paper, and the lithium recovery system was applied to extract lithium from brine and concentrated seawater. The extraction capacity of Li + reached 34.31 mg· (1 g LiMn 2 O 4 ) −1 at 1.2 V. With higher reaction rate and lower energy consumption, 25 °C (room temperature) was considered as the appropriate temperature. The system still remained high selective for Li + even in the presence of impurity ions (K + , Na + , Mg 2+ , Ca 2+ ). With simulated brine and concentrated seawater as source solutions, the concentrations of Na + , Mg 2+ and Ca 2+ were reduced more than 300, 70 and 100 times, consuming 18–19 W h per mole of lithium recovered. And the electrodes still had high separation coefficients of Li + and Me n+ (Na + , Mg 2+ , Ca 2+ ) after five cycles although a slight drop was existing. [ABSTRACT FROM AUTHOR]