Linear Sweep Voltammetry Measurements Research Articles

Potential Modulation on Total Internal Reflection Ellipsometry.

Electrochemical-total internal reflection ellipsometry (EC-TIRE) has been proposed as a technique to observe the redox reactions on the electrode surface due to its high phase sensitivity to the electrolyte/electrode interface. In this paper, we mainly focus on the influence of the potential modulation on the TIRE response. The analysis suggests that both dielectric constant variation of gold and the electric double layer transformation would modulate the reflection polarization of the surface. For a nonfaradaic process, the signal of TIRE would be proportional to the potential modulation. To testify the analysis, linear sweep voltammetry and open circuit measurement have been performed. The results strongly support the system analysis.

Enhanced Photoelectrocatalytic Activity of a Novel Bi2O3–BiPO4 Composite Electrode for the Degradation of Refractory Pollutants under Visible Light Irradiation

A novel Bi2O3–BiPO4 composite electrode was successfully synthesized by the method of electrophoretic deposition, electrodeposition, and calcination in a proper sequence. The prepared electrodes were characterized by X-ray diffractometry (XRD) and scanning electronic microscopy (SEM). Linear sweep voltammetry (LSV) and photocurrent decay curves measurement indicated that the Bi2O3–BiPO4 composite electrode exhibited better photoelectrochemical (PEC) activity than either pure Bi2O3 or BiPO4 electrode. Incident photon to current conversion efficiency (IPCE) and electrochemical impedance spectra (EIS) measurements revealed that the composite electrode significantly improved the efficiency of charge transfer and decreased the recombination of photogenerated charges. Furthermore, the composite electrode also displayed higher efficiency and stability in the PEC degradation of organic pollutants. The p–n junction structure of the Bi2O3–BiPO4 composite electrode was most likely responsible for the enhanced PEC ac...

Sauna-like process prepared periodic molybdenum metal catalytic electrodes and their applications in water reduction

To verify that the molybdenum metals exhibit similar catalysis characteristics as the related molybdenum compounds, i.e. molybdenum selenide (MoSe2) and molybdenum sulfide (MoS2) which have been well known as the high-performing catalysts for hydrogen evolution reactions, we may thus seek a low-cost, process-simplified, scalable, and highly-catalytic counterpart. We have grown periodic molybdenum (Mo) metal catalytic electrodes by employing self-assembled polystyrene (PS) spheres prepared by a sauna-like method as templates, followed by a reactive ion etching (RIE) process with oxygen gas and a double-layer deposition by low-temperature magnetron sputtering. By controlling the etching time of oxygen gas on PS spheres during the RIE process, the lateral and vertical feature sizes of Mo catalytic electrodes can be efficiently controlled, thereby having various surface area ratios. According to surface morphologies from atomic force microscopy, electrochemical linear sweep voltammetry, Tafel, and impendency measurements, we have found that the surface roughness and surface area ratios of Mo metal catalytic electrodes can be enhanced by prolonging the etching times of PS spheres, thereby reducing the charge transfer resistances and Tafel slopes, and then improving the hydrogen evolution reactions at the catalysts/electrolyte interfaces. We attribute this improvement to the fact that the Mo metal catalytic electrodes can efficiently form beneficial Schottky junctions with the electrolyte to enhance the carrier transportation, and the increased surface area ratios can improve the effective area of the Schottky junctions, thereby enhancing the carrier transportation at the catalysts/electrolyte interfaces. Tafel slope of the periodic molybdenum (Mo) metal catalytic electrodes in our work is as low as about 53.9 mV/dec, equivalent to highly catalytic materials MoS2 (55 mV/dec) and MoSe2 (105-120 mV/dec). The proposed periodic Mo catalytic electrodes, which combine a simple sauna-like self-assembly process with a double-layer Mo architecture is scalable and simple; and the surface area of periodic molybdenum (Mo) metal catalytic electrodes can also be flexibly controlled, so that the low-temperature magnetron sputtered Mo metal catalytic electrodes are cost-effective and highly compatible with various photovoltaic devices, highlighting the great potential to form high efficient monolithic solar-water-splitting devices.

Study of the influence of the microstructure on the corrosion properties of pure copper

Different thermomechanical processes have been used to modify the microstructure of elelctrolytic tough pitch copper (ETP‐Cu) in terms of texture, mean grain and grain boundary length fraction. Electron backscatter diffraction (EBSD) and linear sweep voltammetry measurements were performed to study the relation between the macroscopic electrochemical behaviour and the microstructure. FE‐SEM was used to visualise the surface after the potentiodynamic scans. The results indicate that there is only a small influence of the microstructure on the global electrochemical response of pure copper. The previously reported influence of the crystallographic orientation and grain boundary characteristics on the local corrosion behaviour of pure copper are not clearly reflected in the macroscopic electrochemical response.

Effect of various electrophoretically deposited nano‐silica contents on the properties of poly(vinylidene fluoride‐co‐hexafluoropropylene)‐based electrospun polymer electrolytes

AbstractPoly(vinylidene fluoride‐co‐hexafluoropropylene) (P(VDF‐HFP)) based composite polymer electrolyte (CPE) membranes were successfully prepared by electrospinning followed by electrophoretic deposition processes, and desirable polymer electrolytes were obtained after being activated in liquid electrolytes. The physicochemical properties of the CPEs with different electrophoretically deposited nano‐SiO2 contents were investigated by SEM, XRD, TGA, linear sweep voltammetry and electrochemical impedance spectroscopy measurements. When the ratio of electrophoretically deposited nano‐SiO2 to P(VDF‐HFP) is up to 4 wt%, the results show that the CPE membrane presents a very uniform surface with abundant interconnected micropores and possesses excellent mechanical tensile strength with high thermal and electrochemical stability; the ionic conductivity at room temperature can reach 3.361 mS cm−1 and the reciprocal temperature dependence of the ionic conductivity follows a Vogel − Tamman − Fulcher relationship. The interfacial resistance of the assembled Li/CPE/Li simulated cell can rapidly increase to a steady value of about 950 Ω from the initial value of about 700 Ω at 30 °C during 15 days' storage. The battery performance test suggests that the CPE also shows excellent compatible properties with commercial LiCoO2 and graphite materials. © 2015 Society of Chemical Industry

Electrochemical Impedance Studies of CO2 Reduction in Ionic Liquid/Organic Solvent Electrolyte on Au Electrode

Electrochemical reduction of CO2 has been studied in 1-butyl-3-methylimidazolium trifluoromethanesulfonate ([Bmim][CF3SO3])/propylene carbonate (PC) solution on Au electrode. The linear sweep voltammetry measurements show that [Bmim][CF3SO3] has significant catalytic effect toward CO2 reduction. In order to study the mechanism of CO2 reduction in [Bmim][CF3SO3]/PC on Au electrode, the electrochemical impedance spectroscopy is employed. The experiment results show that the electrochemical impedance spectroscopy detected in [Bmim][CF3SO3]/PC is different from that detected in tetrabutylammonium trifluoromethanesulfonate ([Bu4N][CF3SO3])/PC solution. The reasonable explanation is that [Bmim]+ is absorbed on the Au electrode, leading to the formation of ionic liquid film. During the CO2 reduction process, absorbed CO2 is reduced to CO2− radical via single electron transfer. The generated CO2− radical interacts with [Bmim]+ and inducing the formation of [Bmim-CO2](ad). Thus, the activation energy and overpotential of CO2 reduction are reduced. The electrochemical impedance spectroscopy can be used as a methods to investigate the mechanism of CO2 reduction in non-aqueous solution.

An electrochemical study on the influence of sodium molybdate on electrodeposition process and phase composition of ternary Zn–Ni–Mo alloy coatings

Ternary Zn–Ni–Mo alloy coatings were deposited from a citrate-sulphate bath at pH 5.7 containing different amounts of sodium molybdate. The content of molybdenum in the coatings (from 0.3 to 5.2 at.-%) can be easily controlled by increasing sodium molybdate concentration in the plating bath from 0.0025 to 0.05 mol dm− 3, which results also in deposition of smoother deposits. An increase in molybdate concentration leads to the shift of reduction potentials towards more negative values and to the decrease in current efficiency of deposition process. XRD analyses and anodic linear sweep voltammetry (ALSV) measurements demonstrated that at least two phases are formed in the Zn–Ni–Mo alloy: a hexagonal zinc phase or solid solution of nickel in zinc and Ni5Zn21 intermetallic compound. Furthermore, the XRD analyses revealed a third phase, which could be assigned to the oxidised species of molybdenum or other alloying metals.

Direct measurement of methanol crossover fluxes under land and channel in direct methanol fuel cells

Methanol crossover in Direct Methanol Fuel Cells (DMFCs) has a drastic adverse effect on the performance of the cell. Thus, the measurement of methanol crossover flux is of a great importance. In this work, a method is developed to separately measure methanol crossover fluxes under the different regions of the flow field geometry, i.e. under the land and under the channel. Such measurements may further our understanding of this complex phenomenon and thus lead to innovative solutions to mitigate the detrimental effects of methanol crossover. In this method, the anode side of the cell is partially catalyzed in the area of interest (land or channel) and blocked by Teflon® films in other areas, whereas the cathode side is always fully catalyzed. The Linear Sweep Voltammetry measurements show that the methanol crossover flux under the land is higher than that under the channel. The higher crossover flux under the land is attributed to under-land convection. It is believed that under-land convection has duel effects: it causes both a higher methanol concentration and a higher methanol crossover flux under the land.

Effects of Ba Adsorption Layer on NO Electrochemical Reduction Reaction Mechanism

This study investigated the electrochemical reduction of NO and O2 on Pt symmetric electrode by adding NOx adsorbents for the removal of NO from the exhausts of diesel engine or gasoline engine. O2 is excess when compared with NO. Thus, a large mount of external electric field should be consumed by electrochemical decomposition of O2 which gives rise to a low selectivity towards NO. Electrochemical reduction of NO has confronted with the difficult of improving NO selectivity in NO/O2 mixtures. Two cells were prepared and tested: single Pt electrode, Pt electrode with Ba(NO3)2 impregnation. Linear sweep voltammetry(0V~2V), cyclic voltammetry(CV:0.5V~-0.5V) and electrochemical impedance spectroscope(EIS) measurements were carried out between 350℃ and 550℃. The Pt electrode was covered with fine particles on the impregnated electrode surface by scanning electron microscope(SEM). It could be observed from the polarization curves that the Ba impregnated electrode showed higher electrochemical performance than the single Pt electrode especially at low temperatures and high voltages (1.25V to 2V). It can be obtained from the CV tests that the Ba impregnated electrode was superior to the Pt electrode in 800ppm NO. When scanned from 0.5V to -0.5V, the electrochemical performance of NO with O2 was far better than NO especially at high voltages and was close to the performance of O2. While changed the sweep direction backward, NO showed the best electrochemical performance than NO with O2 and O2 near open circuit voltage. EIS results at open circuit voltage revealed that the Ba impregnated electrode exhibited lower resistance than the single Pt electrode due to the decreased polarization resistance in the low-frequency region that dominated the impedance spectra in all atmospheres. The polarization resistances in 800ppm NO showed the smallest while in 8% O2 showed the largest in both electrodes possibly resulted from the generated NO2 formed by NO oxidation on Pt sites, the storage of NOx in the form of Ba(NO3)2 in active sites or the direct electrolysis of Ba(NO3)2 in external electric field that enhanced the reactivity and selectivity of NO reduction. From the impedance analysis using by equivalent circuit model R(CR)(CR)(CR) consisted of serial resistance Rs(related with the conductivity of the electrolyte) and 3 (CR) elements. Results showed that the activation energy of Rs for the two electrodes were nearly the same. The activation energy of the total polarization resistance Rp­ for the Ba impregnated electrode and Pt electrode were 0.874eV and 1.396eV respectively in 800ppm NO and 8% O2. The results were very close to the results obtained in the pure 8% O2 atmosphere. And the activation energy were 0.92eV and 1.50eV for the Ba impregnated electrode and Pt electrode. This was very close to the results of O2 reduction on Pt electrode conducted by Bauerle[1] with the activation energy between 1.43eV and 1.78eV demonstrated that the dissociative adsorption of O2 can be the controlling reaction step. The activation energy in the low frequency(0.01Hz-2Hz) for the three electrodes were close to the results showed by Bauerle resulted from the adsorption, surface diffusion, transfer of O2 and NOx intermediates near/at the triple phase boundary(TPB) and the dissociative adsorption of O2 [1]. The activation energy for the Ba impregnated electrode and Pt electrode in the high frequency were 0.608eV and 0.646eV respectively. The high frequency arc indicated the diffusion of oxide ions to the electrode/electrolyte interface and charge transfer of oxide ions from electrode/electrolyte interface to the electrolyte[2-3]. The activation energy in the middle frequency may be attributed to the charge transfer reactions in the electrode and the dissociative adsorption of O2. And the activation energy were 0.657eV and 1.06eV for the Ba impregnated electrode and Pt electrode. Results showed that the Ba impregnated electrode exhibited lower activation energy in middle and low frequency region indicating the improvement mechanism. Reference [1]J.E. Bauerle, J. Phys. Chem. Solids, 30, 2657 (1969). [2]M. J. Jørgensen, M. Mogensen, J. Electrochem. Soc., 148, A438 (2001). [3]M. L. Traulsenz, K. K. Hansen, J. Electrochem. Soc., 158, P156 (2011). Figure 1

In Operando Vibrational Raman Studies of Chlorine Contamination in Solid Oxide Fuel Cells

Vibrational Raman spectroscopy coupled with voltammetry and impedance measurements was used to explore the effects of chlorine on solid oxide fuel cell (SOFC) performance and durability. Experiments described in this talk use newly developed vibrational Raman methods to acquire vibrational spectra from SOFC anodes exposed to CH3Cl and CH4. SOFC anodes were exposed to 110 ppm dry CH3Cl at 650°C for up to four hours while intermittently exposing the cell to methane for ten minute intervals. In these experiments Raman spectroscopy was used to monitor carbon accumulation kinetics and using a new optically accessible apparatus designed to fit on the stage of the Raman microscope. Electrochemical impedance spectroscopy (EIS) and linear sweep voltammetry (LSV) measurements performed under CH4 following 1 hour of exposure to CH­3Cl showed marked degradation. This degradation was less apparent when the SOFC was operated with H2 following exposure to CH3Cl. Under methane peak power reduced at a rate of 13.8% per hour in the presence of CH3Cl. EIS with CH4 following exposure to CH3Cl showed a small increase of bulk resistance yet consistent polarization resistance (Rpol) until the end of the final exposure, when Rpol increased dramatically. Observable carbon accumulation during CH3Cl exposure became less pronounced over time and eventually stopped accumulating at all suggesting that the primary effect of the Cl contaminant was deactivation of the Ni catalyst. Interestingly, these effects of Cl on SOFC performance with methane proved largely reversible as performance and carbon accumulation behavior recovered upon removal of the CH3Cl.

DC 열플라즈마를 이용하여 제조된 산화철 나노입자의 광 전기화학적 물분해 효율 증가연구

In this research, hematite nanoparticles were synthesized by DC thermal plasma process to increase the overall surface area. The effect of binders on hematite electrodes was investigated by changing the type and composition of binders when preparing electrodes. Nitrogen gas was also added to the DC thermal plasma process in order to dope the hematite with N for enhancing photoelectrochemical properties of hematite nanoparticles. The efficiency of water splitting reaction was measured by linear sweep voltammetry (LSV) under solar simulator. In LSV measurements, the onset potential and maximum current density at a fixed voltage were measured. The durability of electrodes was checked by repeating LSV measurements. CMC (carboxymethyl cellulose) binder with 50 : 1 composition exhibits the highest current density of 12 mA/cm 2 and CMC binder

Preparation of Copper Indium Sulfide Film by Electro-Deposition Method

Abstract Copper indium sulfide (CuInS 2 , CIS 2 ) film was prepared by an electro-deposition method. Uv-vis spectrophotometer test result shows that the band gap of the electroplated CIS 2 film is 1.5 eV. X-ray photoelectron spectroscopy (XPS) analysis reveals that the Cu, In and S signals corresponded to valence state (+1, +3 and −2) of three elements in CIS 2 film, respectively. The photoelectrical properties of the CIS 2 film were characterized by linear sweep voltammetry measurements under the dark and illumination. The I – V characteristic is linear under the dark and illumination, and the slope gap is 0.6×10 −3 . We also simulated the band gap (1.5 eV) of the CIS 2 film with chalcopyrite structure prepared by electroplating experiment using DMol3 and CASTEP modules, respectively. The molecular structure model of electroplated copper indium sulfide film has been established, and the X-ray diffraction simulative spectrum has been obtained by Materials Studio, which has good agreement with the experiment result.

Characterization of Novel Castor Oil-Based Polyurethane Polymer Electrolytes

Castor oil-based polyurethane as a renewable resource polymer has been synthesized for application as a host in polymer electrolyte for electrochemical devices. The polyurethane was added with LiI and NaI in different wt% to form a film of polymer electrolytes. The films were characterized by using attenuated total reflectance-Fourier transform infrared spectroscopy, dynamic mechanical analysis, electrochemical impedance spectroscopy, linear sweep voltammetry and transference number measurement. The highest conductivity of 1.42 × 10−6 S cm−1 was achieved with the addition of 30 wt% LiI and 4.28 × 10−7 S·cm−1 upon addition of 30 wt% NaI at room temperature. The temperature dependence conductivity plot indicated that both systems obeyed Arrhenius law. The activation energy for the PU-LiI and PU-NaI systems were 0.13 and 0.22 eV. Glass transition temperature of the synthesized polyurethane decreased from −15.8 °C to ~ −26 to −28 °C upon salts addition. These characterizations exhibited the castor oil-based polyurethane polymer electrolytes have potential to be used as alternative membrane for electrochemical devices.

Effect of Al2O3 nanowires on the electrochemical properties of di-ureasil-based organic–inorganic hybrid electrolytes

Organic–inorganic hybrid electrolytes based on the reaction of triblock copolymer poly(propylene glycol)-block-poly(ethylene glycol)-block-poly(propylene glycol) bis(2-aminopropyl ether) and 3-(triethoxysilyl)propyl isocyanate doped with lithium trifluoromethanesulfonate and Al2O3 nanowires were synthesized by a sol–gel process. The structural and electrochemical properties of the materials thus obtained were systematically investigated by Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry, thermogravimetric analysis, powder X-ray diffraction, 29Si CPMAS (cross-polarization magic angle spinning) NMR, alternate current impedance, and linear sweep voltammetry measurements. FTIR spectra showed the occurrence of complexation and interaction among the components. The maximum ionic conductivity values of 9.8 × 10−5 S cm−1 and 6.8 × 10−4 S cm−1 were obtained at 30 and 75 °C, respectively, for the solid hybrid electrolyte with a [O]/[Li] ratio of 16 and 1 wt% of Al2O3 nanowires. A Vogel–Tamman–Fulcher-like temperature dependence of ionic conductivity was observed for the hybrid electrolytes doped with fillers. The electrochemical stability window of ~4.0 V makes the organic–inorganic hybrid electrolyte promising for lithium-ion battery application at low voltages.

Fabrication of Vertically aligned Copper Nanotubes as a Novel Electrode for Enzymatic Biofuel Cells

Herein, Laccase catalysed oxygen reduction reaction on polyaniline coated copper nanotube bio-cathode was studied. The copper nanotubes were grown in anodic aluminium oxide template on which conductive polymer polyaniline was electrodeposited. Laccase was covalently immobilized using a linker molecule glutraldehyde. The effective wiring of enzyme with bio-cathode was confirmed by linear sweep voltammetry, chronoamperometry and open circuit potential measurement. All electro analysis was performed in conventional three electrode system using platinum wire counter electrode and Ag/AgCl reference electrode. The bio-cathode in air saturated phosphate buffer showed maximum OCP and current of 0.59V and 140.12μAcm−2 respectively. Moreover, electrochemical impedance analysis confirmed decrease in charge transfer resistance with the immobilization of enzyme on CuNTs/polyaniline electrode. The bio-cathode showed reproducibility and stability over the period of examination.

A Green Route: From Carbon Dioxide to Silyl Substituted Carbonate Electrolytes for Lithium-Ion Batteries

The cyclic carbonates 4-(trimethylsilyl)-1,3-dioxolan-2-one, 4-(triethylsilyl)-1,3-dioxolan-2-one and 4-[2-(trimethylsilyl)ethyl]-1,3-dioxolan-2-one were synthesized via an environmentally friendly synthetic route and applied as electrolytes in lithium-ion battery half-cells. The synthesis was carried out by the catalyzed conversion of CO2 with epoxides using the nontoxic catalysts FeCl2 and tetra-n-butylammonium bromide. Investigations of the LiTFSI solutions with regards to ionic conductivity, viscosity and solvent-salt interaction by NMR spectroscopy reveal a structure-property relationship. Linear sweep voltammetry measurements indicate no decomposition of the silyl carbonates within the electrochemical window of commonly used electrode materials for lithium-ion batteries. The suitability of the compounds as battery electrolytes is shown by half-cell measurements with lithium iron phosphate. The 4-(trimethylsilyl)-1,3-dioxolan-2-one solution not only exhibits the highest conductivity but also a high capacity with superior stability over more than 50 cycles.

In Operando Vibrational Raman Studies of Chlorine Contamination in Solid Oxide Fuel Cells

Vibrational Raman spectroscopy coupled with voltammetry and impedance measurements was used to explore the effects of chlorine on solid oxide fuel cell (SOFC) performance and durability. SOFC anodes were exposed to 110 ppm dry CH3Cl at 650°C for up to four hours while intermittently exposing the cell to methane for ten minute intervals. In these experiments Raman spectroscopy was used to monitor carbon accumulation kinetics. Electrochemical impedance spectroscopy (EIS) and linear sweep voltammetry (LSV) measurements performed under CH4 following 1 hour of exposure to CH3Cl showed marked degradation. This degradation was less apparent when the SOFC was operated with H2 in the presence of CH3Cl. With methane and CH3Cl, peak power diminished at a rate of 14% per hour. Observable carbon accumulation during CH3Cl exposure became less pronounced over time. Eventually, carbon formation was suppressed completely suggesting that the primary effect of the Cl contaminant was deactivation of the Ni catalyst with respect to CH bond dissociation. SOFC performance with H2 in the presence of CH3Cl remained largely unchanged. Interestingly, these effects of Cl on SOFC performance with methane proved partially reversible as electrochemical performance and carbon accumulation behavior were recovered upon removal of the CH3Cl from the fuel feed.

Galvanic deposition of Rh and Ru on randomly structured Ti felts for the electrochemical NH3 synthesis.

Nowadays NH3 is exclusively synthesized by the Haber process. Unfortunately, the energy demand and the CO2 emissions due to H2 production are high. Hydrogen production utilizes precious carbon sources such as coal and natural gas. In the past we proposed an alternative process concept using a membrane electrode assembly in an electrochemical membrane reactor (ecMR). At the anode H2O is oxidized at an IrMMO catalyst to form protons. By applying an external potential to the ecMR N2 is reduced to NH3 at the cathode. Just recently Rh and Ru were identified as possible cathodic electrocatalysts by DFT calculations. We present an easy and highly efficient method for galvanic coatings of Rh and Ru on randomly structured Ti felts to be used in a membrane electrode assembly. Linear sweep voltammetry measurements give a slightly higher activity of Ru for the liquid phase electrochemical NH3 synthesis. The NH4(+) concentration reached is 8 times higher for Ru than for Rh. From an economical point of view, Ru is also more feasible for an electrochemical NH3 synthesis process. Such electrodes can now be evaluated in an ecMR in comparison to recently demonstrated Ti-based electrodes.

Impact of Load Cycling at High Current Densities on the Degradation Behavior of Membrane-Electrode-Assemblies

For the establishment in the field of renewable energy and energy converters, High Temperature Polymer Electrolyte Membrane fuel cells (HT-PEMFC) need, next to an increase of performance, an improvement in their lifetime expectancy. The amendment of both, durability and performance, requires a better understanding of degradation effects and – processes within the fuel cell. The term degradation can be defined as a decrease of performance as a function of operation time. The degeneration of fuel cells can be caused by thermal, chemical and mechanical degradation. The debasement due to mechanical stress caused by severe operational conditions lies in the focus of this work. Accelerated stress tests (AST) at high current densities will be carried out with membrane electrode assemblies (MEA) from two different providers. AST are a good instrument to determine the durability of a MEA and its components in a shorter time span. A standard AST is an operation procedure with a load cycling between moderate current densities (0.3 – 0.6 A/cm²) and open circuit voltage (OCV). In our case, we will concentrate on load cycling treatment with higher current densities between 0.6 and 1.0 A/cm². The operation mode is presented in figure 1. The highest current (1.0 A/cm²) density will be kept for 16 min and the holding time of the lower value (0.6 A/cm²) will be 4 min. One cycle lasts 6 hours and ends with a 10 min OCV phase. The development of the OCV is a good indicator of the state of the membrane (1). After 17 hours of load cycling, the MEA will be characterized with electrochemical measurements like polarization curves, electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and linear sweep voltammetry (LSV) (2). After 7 hours of characterization, the load cycling takes again place in the operation procedure. This method will be repeated day by day for one week.Next to the electrochemical characterization, selected MEAs will be also analyzed ex-situ by imaging procedures like Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and micro-computed tomography (µ-CT). The combination of electrochemical and imaging investigations allows a more detailed and holistic research of degradation effects and defects within the MEA.With support of the µ-CT, structural changes within the MEA due to the high current densities can be observed. Expected defects like for example pin holes and fiber intrusion can be visualized. These errors (and their influences) on the fuel cell performance can be analyzed and confirmed by LSV measurements (3).The electron microcopy facilitates the examination of microstructure changes, for example cracking of the catalyst layer or delamination (4). TEM measurements permit the ante and post mortem investigations of the catalyst-particle-formation (5) and the influence of the advanced AST on this development. Figure 1 : Overview of load cycling testing procedure at high current densities

Synthesis of few-layered MoS₂ nanosheet-coated electrospun SnO₂ nanotube heterostructures for enhanced hydrogen evolution reaction.

In this work, we report the fabrication of low crystalline, few-layered MoS₂ nanosheet-coated electrospun SnO₂ nanotube (MoS₂/SnO₂) heterostructures with three-dimensional configurations by electrospinning combined with a one-step solvothermal approach. The morphologies and compositions of the as-prepared hybrid nanotubes were characterized by field-emission scanning electron microscopy, transmission electron microscopy, ICP-AES, BET method, X-ray diffraction and X-ray photoelectron spectroscopy. Results show that SnO₂ nanotubes are uniformly covered by sheet-like MoS₂ subunits on both outer and inner surfaces. The electrocatalytic activity of MoS₂/SnO₂ heterostructures towards a hydrogen evolution reaction was examined using linear sweep voltammetry and AC impedance measurements. It is shown that the MoS₂/SnO₂ modified electrode exhibits excellent catalytic activity for hydrogen evolution with low overpotential, a small Tafel slope and high current density.