text:
177 results found
Lopes T, Beruski O, Manthanwar A, et al., Spatially resolved oxygen reaction, water, and temperature distribution: Experimental results as a function of flow field and implications for polymer electrolyte fuel cell operation, Applied Energy, ISSN: 0306-2619
In situ and ex situ spatially-resolved techniques are employed to investigate reactant distribution and its impacts in a polymer electrolyte fuel cell. Temperature distribution data provides further evidence for secondary flows inferred from reactant imaging data, highlighting the contribution of convection in heat as well as reactant distribution. Water build-up from neutron tomography is linked to component degradation, matching the pattern seen in the reactant distribution and thus suggesting that high, non-uniform local current densities shape degradation patterns in fuel cells. The correlations shown between different techniques confirm the use of the versatile reactant imaging technique, which is used to compare commonly used flow field designs. Among serpentine-type designs, the single serpentine is superior in both equivalent current density and reactant distribution, showing large contributions from convective flow. On the other hand, the interdigitated design is shown to produce larger equivalent current densities, while showing a somewhat poorer reactant distribution. Considering the correlations drawn between the techniques, this suggests that the interdigitated design compromises durability in favour of power output. The results highlight how established techniques provide a robust background for the use of a new and flexible imaging technique toward designing advanced flow fields for practical fuel cell applications.
Montelongo Y, Sikdar D, Ma Y, et al., 2019, Author Correction: Electrotunable nanoplasmonic liquid mirror., Nat Mater, ISSN: 1476-1122
In the version of this Article originally published, the last sentence of the acknowledgements incorrectly read 'L.V. acknowledges the support of a Marie Skodowska-Curie fellowship (N-SHEAD)'; it should have read 'L.V. and D.S. acknowledge the support of Marie Skłodowska-Curie fellowships, N-SHEAD and S-OMMs, respectively'.
Castanheira L, Bedouet M, Kucernak A, et al., 2019, Influence of microporous layer on corrosion of metallic bipolar plates in fuel cells, Journal of Power Sources, Vol: 418, Pages: 147-151, ISSN: 0378-7753
The effect of the presence of a microporous layer on the propensity for corrosion of metallic bipolar plates in an operating polymer electrolyte membrane fuel cell is investigated using an in situ reference electrode array. The local potential at the surface of the cathode bipolar plate is significantly more negative in the presence of the microporous layer, which is attributed to the higher ionic resistance of the aqueous phase in the reactant transport layer associated with more effective removal of water from the catalyst layer/reactant transport layer interface. As a result the bipolar plate is effectively shielded from elevated potentials that may be present at the cathode electrode, even during start-up and shutdown of the cell. Revision of ex situ test protocols for candidate bipolar plate materials, surface treatments and coatings is recommended to reduce unnecessary conservatism in testing.
Malko D, Guo Y, Jones P, et al., 2019, Heterogeneous iron containing carbon catalyst (Fe-N/C) for epoxidation with molecular oxygen, Journal of Catalysis, Vol: 370, Pages: 357-363, ISSN: 0021-9517
Pyrolized transition metal and nitrogen containing carbon materials (M-N/C) have shown promising activities as electrocatalysts for oxygen reduction reactions (ORR) in fuel cell cathodes. Similar materials have recently gained interest as heterogeneous catalysts. We report that ORR-active heterogeneous M-N/C materials can catalyze the chemical epoxidation of olefins with molecular oxygen and two equivalents of aldehyde at room temperature and ambient pressure. The observed yield and selectivity is higher than that for homogeneous analogues and the catalysts achieve TOF > 2700 h−1 and TON > 16,000. The ability to recycle the catalyst several times is also demonstrated.
Rubio-Garcia J, Kucernak A, Zhao D, et al., 2019, Hydrogen/manganese hybrid redox flow battery, JPhys Energy, Vol: 1, ISSN: 2515-7655
Electrochemical energy storage is a key enabling technology for further integration of renewables sources. Redox flow batteries (RFBs) are promising candidates for such applications as a result of their durability, efficiency and fast response. However, deployment of existing RFBs is hindered by the relatively high cost of the (typically vanadium-based) electrolyte. Manganese is an earth-abundant and inexpensive element that is widely used in disposable alkaline batteries. However it has hitherto been little explored for RFBs due to the instability of Mn(III) leading to precipitation of MnO2 via a disproportionation reaction. Here we show that by combining the facile hydrogen negative electrode reaction with electrolytes that suppress Mn(III) disproportionation, it is possible to construct a hydrogen/manganese hybrid RFB with high round trip energy efficiency (82%), and high power and energy density (1410 mW cm−2, 33 Wh l−1), at an estimated 70% cost reduction compared to vanadium redox flow batteries.
Ma Y, Zagar C, Klemme DJ, et al., 2018, A tunable nanoplasmonic mirror at an electrochemical interface, ACS Photonics, Vol: 5, Pages: 4604-4616, ISSN: 2330-4022
Designing tunable optical metamaterials is one of the great challenges in photonics. Strategies for reversible tuning of nanoengineered devices are currently being sought through electromagnetic or piezo effects. For example, bottom-up self-assembly of nanoparticles at solid | liquid or liquid | liquid interfaces can be used to tune optical responses by varying their structure either chemically or through applied voltage. Here, we report on a fully reversible tunable-color mirror based on a TiN-coated Ag substrate immersed in an aqueous solution of negatively charged Au-nanoparticles (NPs). Switching electrode potential can be used to fully control the assembly/disassembly of NPs at the electrode | electrolyte interface within a 0.6 V wide electrochemical window. The plasmon coupling between the electrode and the adsorbed NP array at high positive potentials produces a dip in the optical reflectance spectrum, creating the "absorber" state. Desorption of NPs at low potentials eliminates the dip, returning the system to the reflective "mirror" state. The intensity and wavelength of the dip can be finely tuned through electrode-potential and electrolyte concentration. The excellent match between the experimental data and the theory of optical response for such system allows us to extract valuable information on equilibrium and kinetic properties of NP-assembly/disassembly. Together with modeling of the latter, this study promotes optimization of such meta-surfaces for building electrotunable reflector devices.
Tariq F, Rubio-Garcia J, Yufit V, et al., 2018, Uncovering the mechanisms of electrolyte permeation in porous electrodes for redox flow batteries through real time in situ 3D imaging, SUSTAINABLE ENERGY & FUELS, Vol: 2, Pages: 2068-2080, ISSN: 2398-4902
Riedel R, Malko D, Seel A, et al., 2018, Ion pairing and stability of alkalides in organic solutions, 256th National Meeting and Exposition of the American-Chemical-Society (ACS) - Nanoscience, Nanotechnology and Beyond, Publisher: AMER CHEMICAL SOC, ISSN: 0065-7727
Rubio-Garcia J, Kucernak ARJ, Charleson A, 2018, Direct visualization of reactant transport in forced convection electrochemical cells and its application to Redox Flow Batteries, Electrochemistry Communications, Vol: 93, Pages: 128-132, ISSN: 1388-2481
A novel, simple and low cost electrochemiluminescence imaging method for monitoring mass transport phenomena in a redox flow battery-like system is presented. Luminol solutions were pumped through a flow field (FF) with a given design. At the flowfield/electrode interface light is emitted upon dye oxidation allowing direct visualization of channels, U-bends and regions of poor wetting. Image analysis allows direct visualization of reactant distribution and poor mass transport through tortuous materials. These results were compared with the experimental performance of an all‑vanadium redox flow battery with different FFs as a function of flow and good correlation achieved.
Jackson C, Smith GT, Markiewicz M, et al., 2018, Support induced charge transfer effects on electrochemical characteristics of Pt nanoparticle electrocatalysts, Journal of Electroanalytical Chemistry, Vol: 819, Pages: 163-170, ISSN: 1572-6657
The electrokinetic properties of Pt nanoparticles supported on Carbon (Pt/C) and Boron Carbide-Graphite composite (Pt/BC) are compared over a wide potential range. The influence of the support on the electronic state of Pt was investigated via in-situ X-ray Absorption Spectroscopy. Pt d-band filling, determined from XANES white line analysis, was lower and nearly constant between 0.4 and 0.95V vs. RHE for Pt/BC, indicating more positively charged particles in the double layer region and a delay in the onset of oxide formation by about 0.2V compared to the Pt/C catalyst, which showed a marked increase in d-band vacancies above 0.8V vs. RHE. Moreover, δμ analysis of the XANES data indicated a lack of sub-surface oxygen for the Pt/BC catalyst compared to the Pt/C catalyst above 0.9V vs. RHE. Additional anion adsorption on the Pt/BC in the double layer region, detected by CO displacement, was also confirmed by XANES analysis of the d-band occupancy. The H 2 oxidation activities of electrodes with low catalyst loadings were assessed under high mass transport conditions using the floating electrode methodology. The metal-support interaction between the Pt and BC support improved the maximum hydrogen oxidation current density by 1.4 times when compared to Pt/C.
Jaouen F, Jones D, Coutard N, et al., 2018, Toward platinum group metal-free catalysts for hydrogen/airproton-exchange membrane fuel cells, Johnson Matthey Technology Review, Vol: 62, Pages: 231-255, ISSN: 2056-5135
The status, concepts and challenges toward catalysts free of platinum group metal (pgm) elements for proton-exchange membrane fuel cells (PEMFC) are reviewed. Due to the limited reserves of noble metals in the Earth's crust, a major challenge for the worldwide development of PEMFC technology is to replace Pt with pgm-free catalysts with sufficient activity and stability. The priority target is the substitution of cathode catalysts (oxygen reduction) that account for more than 80% of pgms in current PEMFCs. Regarding hydrogen oxidation at the anode, ultralow Pt content electrodes have demonstrated good performance, but alternative non-pgm anode catalysts are desirable to increase fuel cell robustness, decrease the H2 purity requirements and ease the transition from H2 derived from natural gas to H2 produced from water and renewable energy sources.
Lee M-R, Lee H-Y, Yim S-D, et al., 2018, Effects of Ionomer Carbon Ratio and Ionomer Dispersity on the Performance and Durability of MEAs, FUEL CELLS, Vol: 18, Pages: 129-136, ISSN: 1615-6846
Park JY, Kwak DH, Ma KB, et al., 2018, Enhanced oxygen reduction reaction of Pt deposited Fe/N-doped bimodal porous carbon nanostructure catalysts, Journal of Catalysis, Vol: 359, Pages: 46-54, ISSN: 0021-9517
© 2018 Elsevier Inc. For commercialization of proton exchange membrane fuel cells (PEMFCs), the loading amount of Pt-based cathode catalysts for oxygen reduction reaction (ORR) needs be significantly reduced. In this study, we propose Pt catalysts supported by an iron/nitrogen-doped porous carbon (FeNC) nanostructure having a catalytic activity for ORR in order to significantly reduce the utilization of Pt. The FeNC nanostructure was prepared using a template method with 50 and 500 nm SiO 2 beads and phthalocyanine as a dopant and carbon source. The nanosized Pt catalysts with different loading weights (5, 10, 20, 30 wt%) were uniformly deposited on the FeNC with a bimodal porous crystalline doped carbon nanostructure using an electron beam radiation method. In particular, the cathode catalyst having 5 wt% Pt on FeNC (Pt5/FeNC) exhibited enhanced ORR mass activities of 2.19 and 2.58 A mg Pt −1 at 0.9 V measured by electrochemical half cells in acidic and alkaline media, respectively, compared to a commercial Pt(20 wt%)/C (Pt20/C). Furthermore, Pt5/FeNC showed a higher mass activity of 18.76 A mg Pt −1 at 0.6 V as a unit cell performance than that of the commercial catalyst. The improved ORR activity of Pt/FeNC might be synergistically attributed to the homogeneous dispersion of Pt nanoparticles on the bimodal porous doped carbon nanostructure, the interaction (electronic effect) between the metallic catalyst and the doped support, and the dual catalytic effect of both Pt and the doped carbon nanostructure.
zalitis C, Kucernak ARJ, sharman J, et al., 2017, Design principles for platinum nanoparticles catalysing electrochemical hydrogen evolution and oxidation reactions: edges are much more active than facets, Journal of Materials Chemistry A, Vol: 5, Pages: 23328-23338, ISSN: 2050-7496
Improving the performance of hydrogen evolution and oxidation reactions using precious metal catalysts is key in reducing the cost of electrolysers and fuel cells. By considering the performance of these reactions as a function of platinum particle size (2.1–15 nm) under high mass transport conditions in acids, we find that the activity is composed of two components which vary in a defined way with the particle size. Geometrical considerations and electrokinetic modelling suggest that these two components correspond to the response of edges/vertices and the response of facets (Pt(100) and Pt(111)). Edges and vertices are much more active towards the hydrogen reaction. This assignment also rationalises the poor performance of platinum in alkaline environments. We predict that "ideal" particles made up of only edges/vertices would allow fuel cells and electrolysers to operate with only 1 μgPt cm−2 – about two to three orders of magnitude lower than what is currently used.
Beruski O, Lopes T, Kucernak ARJ, et al., 2017, Investigation of convective transport in the so-called "gas diffusion layer" used in polymer electrolyte fuel cell, Physical Review Fluids, Vol: 2, ISSN: 2469-990X
Recent experimental data on a fuel-cell-like system revealed insights into the fluid flow in both free and porous media. A computational model is used to investigate the momentum and species transport in such a system, solved using the finite element method. The model consists of a stationary, isothermal, diluted species transport in free and porous media flow. The momentum transport is treated using different formulations, namely, Stokes-Darcy, Darcy-Brinkman, and hybrid Stokes-Brinkman formulations. The species transport is given by the advection equation for a reactant diluted in air. The formulations are compared to each other and to the available experimental data, where it is concluded that the Darcy-Brinkman formulation reproduces the data appropriately. The validated model is used to investigate the contribution of convection in reactant transport in porous media of fuel cells. Convective transport provides a major contribution to reactant distribution in the so-called diffusion media. For a serpentine channel and flow with Re=260–590, convection accounts for 29–58% of total reactant transport to the catalyst layer.
Montelongo Y, Sikdar D, Ma Y, et al., 2017, Electrotunable nanoplasmonic liquid mirror, Nature Materials, Vol: 16, Pages: 1127-1135, ISSN: 1476-1122
Recently, there has been a drive to design and develop fully tunable metamaterials for applications ranging from new classes of sensors to superlenses among others. Although advances have been made, tuning and modulating the optical properties in real time remains a challenge. We report on the first realization of a reversible electrotunable liquid mirror based on voltage-controlled self-assembly/disassembly of 16 nm plasmonic nanoparticles at the interface between two immiscible electrolyte solutions. We show that optical properties such as reflectivity and spectral position of the absorption band can be varied in situ within ±0.5 V. This observed effect is in excellent agreement with theoretical calculations corresponding to the change in average interparticle spacing. This electrochemical fully tunable nanoplasmonic platform can be switched from a highly reflective 'mirror' to a transmissive 'window' and back again. This study opens a route towards realization of such platforms in future micro/nanoscale electrochemical cells, enabling the creation of tunable plasmonic metamaterials.
Malko D, Kucernak ARJ, 2017, Kinetic isotope effect in the oxygen reduction reaction (ORR) over Fe-N/C catalysts under acidic and alkaline conditions., Electrochemistry Communications, Vol: 83, Pages: 67-71, ISSN: 1388-2481
Heat treated Fe-N/C materials which are highly effective oxygen reduction catalysts in alkaline and acid, show a significant kinetic isotope effect (KIE). The values in acid (~3.4) and alkaline (~2.5) are much larger than the value for the metal free catalyst in acid (~1.8) suggesting that the rate determining step (RDS) is a proton coupled electron transfer in acid with a significant pathway involving a proton independent step under an alkaline environment
Bazant M, Bennewitz R, Bocquet L, et al., 2017, Electrotunable wetting, and micro- and nanofluidics: general discussion, Publisher: ROYAL SOC CHEMISTRY
Symianakis E, Kucernak A, 2017, Embedded atom method interatomic potentials fitted upon density functional theory calculations for the simulation of binary Pt-Ni nanoparticles, Computational Materials Science, Vol: 133, Pages: 185-193, ISSN: 0927-0256
Embedded Atom Method (EAM) potentials have been fitted for the atomistic simulation of small, 2–5 nm, binary, PtANi, nanoparticles completely from Density Functional Theory (DFT) total energy calculations.The overall quality of the DFT calculations and the final potential is obtained through the independentcalculation of an array of properties of the pure metals and the stable alloys, which arenormally used for the fitting of interatomic potentials. The ability of the fitted potentials to simulatenanostructures is evaluated by the reproduction of binary nanoslabs with thickness 1 nm, and nanoparticlesin the extreme case of the smallest icosahedrons possible, with diameter 0.6 nm. The usedapproach requires high quality of convergence but otherwise low cost DFT as it is based on static totalenergy calculations. It also provides objective criteria for the evaluation of the fitted potentials during fittingand has been implemented with the open source code GULP
Cousens N, Kucernak ARJ, 2017, Reversible ultralow-voltage liquid-liquid electrowetting without a dielectric layer, Faraday Discussions, Vol: 199, Pages: 63-73, ISSN: 1364-5498
Electrowetting-on-dielectric devices typically have operating voltages of 10-20 V. A reduction in the operating voltage could greatly reduce the energy consumption of these devices. Here, the fully reversible one electrolyte electrowetting of a droplet on a solid metal surface is reported for the first time. A reversible change of 29o for an 800 mV step is achieved. The effect of surface roughness, electrolyte composition, electrolyte concentration and droplet composition is investigated. It is found that there is a dramatic dependence of the reversibility and hysteresis of the system on these parameters, contrary to theoretical predictions. When a 3-chloro-1-propanol droplet is used, a system with no hysteresis and a 40o change in angle is achieved.
Velleman L, Sikdar D, Turek V, et al., 2016, Tuneable 2D self-assembly of plasmonic nanoparticles at liquid | liquid interfaces, Nanoscale, Vol: 8, Pages: 19229-19241, ISSN: 2040-3372
Understanding the structure and assembly of nanoparticles at liquid | liquid interfaces is paramount to their integration into devices for sensing, catalysis, electronics and optics. However, many difficulties arise when attempting to resolve the structure of such interfacial assemblies. In this article we use a combination of X-ray diffraction and optical reflectance to determine the structural arrangement and plasmon coupling between 12.8 nm diameter gold nanoparticles assembled at a water | 1,2-dichloroethane interface. The liquid | liquid interface provides a molecularly flat and defect-correcting platform for nanoparticles to self-assemble. The amount of nanoparticles assembling at the interface can be controlled via the concentration of electrolyte within either the aqueous or organic phase. At higher electrolyte concentration more nanoparticles can settle at the liquid | liquid interface resulting in a decrease in nanoparticle spacing as observed from X-ray diffraction experiments. The coupling of plasmons between the nanoparticles as they come closer together is observed by a red-shift in the optical reflectance spectra. The optical reflectance and the X-ray diffraction data are combined to introduce a new 'plasmon ruler'. This allows extraction of structural information from simple optical spectroscopy techniques, with important implications in understanding the structure of nanoparticle films at liquid interfaces and their self-assembly.
Kucernak ARJ, kakati, Fahy KF, 2016, Using corrosion-like processes to remove poisons from electrocatalysts: a viable strategy to chemically regenerate irreversibly poisoned polymer electrolyte fuel cells, Electrochimica Acta, Vol: 222, Pages: 888-897, ISSN: 1873-3859
Poisoning of Pt/C catalysts due to SO2 on a rotating disk electrode (RDE), and as part of the cathode layer in a single cell fuel cell and fuel cell stack are studied in terms of the system performance, and the effect of electrochemical and chemical post treatment to remove the adsorbed sulphur containing species. It is found that external polarisation can only recover the ORR performance of catalyst on an RDE after SO2 poisoning when an applied potential of 1.6 V(RHE) is used for 1 ks. An alternative approach is to use ozone, as in the presence of this species, the electrode potential is raised to ~1.6V(RHE) due to the high potential of the ozone reduction reaction. The high open circuit potential leads to a mixed potential and was found also to be highly efficient at removing the poison via coupled ozone reduction and poison oxidation. The ozone process is found to work efficiently at the catalyst level as shown through rotating disk electrode studies and also in single cell fuel cells. Furthermore we demonstrate for the first time the recovery of a SO2 poisoned fuel cell stack using the mixed-potential approach and ozone as a reactant. The cleaning process is fast (~10 minutes), occurs at room temperature, and does not require any special modification to the fuel cell. The process may be applicable to a wide range of poisons which can be oxidatively removed from platinum at high potentials.
Kucernak A, Malko D, Lopes T, 2016, Performance of Fe-N/C oxygen reduction electrocatalysts towards NO−₂, NO, and NH₂OH electroreduction from fundamental insights into the active center to a new method for environmental nitrite destruction, Journal of the American Chemical Society, Vol: 138, Pages: 16056-16068, ISSN: 1520-5126
Although major progress has recently been achieved through ex situ methods, there is still a lack of understanding of the behavior of the active center in non-precious metal Fe–N/C catalysts under operating conditions. Utilizing nitrite, nitric oxide, and hydroxylamine as molecular probes, we show that the active site for the oxygen reduction reaction (ORR) is different under acidic and alkaline conditions. An in-depth investigation of the ORR in acid reveals a behavior which is similar to that of iron macrocyclic complexes and suggests a contribution of the metal center in the catalytic cycle. We also show that this catalyst is highly active toward nitrite and nitric oxide electroreduction under various pH values with ammonia as a significant byproduct. This study offers fundamental insight into the chemical behavior of the active site and demonstrates a possible use of these materials for nitrite and nitric oxide sensing applications or environmental nitrite destruction.
Chakrabarti BK, Nir DP, Yufit V, et al., 2016, Studies of performance enhancement of rGO-modified carbon electrodes for Vanadium Redox Flow Systems, ChemElectroChem, Vol: 4, Pages: 194-200, ISSN: 2196-0216
Reduced graphene oxide (rGO) suspended in an N,N′-dimethylformamide (DMF) solvent underwent electrophoretic deposition (EPD) on carbon paper (CP) electrodes. X-ray computed micro-tomography (XMT) indicates a 24 % increase in the specific surface area of CP modified with rGO in comparison to the untreated sample. Furthermore, XMT confirms that the deposition also penetrates into the substrate. Raman analysis shows that the rGO deposited is more amorphous than the CP electrode. A significant reduction in charge-transfer resistance of the VO2+/VO2+ reaction is also observed (from impedance measurements) in modified samples in comparison to untreated CP electrodes.
Malko D, Kucernak A, Lopes T, 2016, In-situ electrochemical quantification of active sites in Fe-N/C non-precious metal catalysts, Nature Communications, Vol: 7, ISSN: 2041-1723
The economic viability of low temperature fuel cells as clean energy devices is enhanced by the development of inexpensive oxygen reduction reaction catalysts. Heat treated iron and nitrogen containing carbon based materials (Fe–N/C) have shown potential to replace expensive precious metals. Although significant improvements have recently been made, their activity and durability is still unsatisfactory. The further development and a rational design of these materials has stalled due to the lack of an in situ methodology to easily probe and quantify the active site. Here we demonstrate a protocol that allows the quantification of active centres, which operate under acidic conditions, by means of nitrite adsorption followed by reductive stripping, and show direct correlation to the catalytic activity. The method is demonstrated for two differently prepared materials. This approach may allow researchers to easily assess the active site density and turnover frequency of Fe–N/C catalysts.
Lopes T, Kucernak A, Malko D, et al., 2016, Mechanistic Insights into the Oxygen Reduction Reactionon Metal–N–C Electrocatalysts under Fuel Cell Conditions, ChemElectroChem, Vol: 3, Pages: 1580-1590, ISSN: 2196-0216
Three different transition metal-C-N catalysts are tested under a range of fuel cell conditions. It is found that common features of the polarisation curve can be explained by a change in electrocatalytic mechanism. Utilising a simple model to quantify the change in mechanisms, iR free results of the fuel cell experiments are fit and found to be represented by a common set of parameters. The change in mechanism is assumed to be a switch from four electron reduction of oxygen to water to a two electron reduction to hydrogen peroxide followed by disproportionation of the hydrogen peroxide to water and oxygen. The data is used to estimate a mass specific exchange current density towards the ORR in the range 10-11-10-13 A g-1 depending on the catalyst. For the reduction of oxygen to hydrogen peroxide, the mass specific exchange current density is estimated to be in the range 10-2-10-3 A g-1. Utilising the electrokinetic model, it is shown how the mass transport losses can be extracted from the polarisation curve. For all three catalyst layers studied, these mass transport losses reach about 100mV at a current density of 1 A cm-2. Finally a discussion of the performance and site density requirements of the non-precious metal catalysts are provided, and it is estimated that the activity towards the ORR needs to be increased by an order of magnitude, and the site density by two/three orders of magnitude in order to compete with platinum as an ORR electrocatalyst.
Malko D, lopes T, Ticianelli E, et al., 2016, A catalyst layer optimisation approach using electrochemical impedance spectroscopy for PEM fuel cells operated with pyrolysed transition metal-N-C catalysts, Journal of Power Sources, Vol: 323, Pages: 189-200, ISSN: 0378-7753
The effect of the ionomer to carbon (I/C) ratio on the performance of single cell polymer electrolyte fuel cells is investigated for three different types of non-precious metal cathodic catalysts. Polarisation curves as well as impedance spectra are recorded at different potentials in the presence of argon or oxygen at the cathode and hydrogen at the anode. It is found that a optimised ionomer content is a key factor for improving the performance of the catalyst. Non-optimal ionomer loading can be assessed by two different factors from the impedance spectra. Hence this observation could be used as a diagnostic element to determine the ideal ionomer content and distribution in newly developed catalyst-electrodes. An electrode morphology based on the presence of inhomogeneous resistance distribution within the porous structure is suggested to explain the observed phenomena. The back-pressure and relative humidity effect on this feature is also investigated and supports the above hypothesis. We give a simple flowchart to aid optimisation of electrodes with the minimum number of trials.
Kucernak ARJ, Zalitis CM, 2016, General Models for the Electrochemical Hydrogen Oxidation and Hydrogen Evolution Reactions – Theoretical Derivation and Experimental Results Under Near Mass-Transport Free Conditions, Journal of Physical Chemistry C, Vol: 120, Pages: 10721-10745, ISSN: 1932-7455
Full derivations of Heyrovsky-Volmer (HV), Tafel-Volmer(TV), Heyrovsky-Tafel(HT), and Heyrovsky-Tafel-Volmer(HTV) mechanisms under steady state conditions are provided utilising a new theoretical framework which allows better understanding of the each of the mechanistic currents and part currents. Simple and easily implemented equations are presented, which provide both the hydrogen coverage and electrochemical current as a function of overpotential and relevant kinetic parameters. It is shown how these responses are governed by a set of dimensionless parameters associated with the ratio of electrokinetic parameters. For each of the different mechanisms, an "atlas" of Hads coverage with overpotential and corresponding current density is provided, allowing an understanding of all possible responses depending on the dimensionless parameters. Analysis of these mechanisms provides the limiting reaction orders of the exchange current density for protons and bimolecular hydrogen for each of the different mechanisms, as well as the possible Tafel slopes as a function of the molecular symmetry factor, . Only the HV mechanism is influenced by pH whereas the TV,HT, and HTV mechanisms are not. The cases where the equations simplify to limiting forms are discussed. Analysis of the exchange current density from experimental data is discussed, and it is shown that fitting the linear region around the equilibrium potential underestimates the true exchange current density for all of the mechanisms studied. Furthermore, estimates of exchange current density via back-extrapolation from large overpotentials is also shown to be highly inaccurate. Analysis of Tafel slopes is discussed along with the mechanistic information which can and cannot be determined. The new models are used to simultaneously fit sixteen experimental responses of Pt/C electrodes in acid towards the her/hor as a function of , pH, p(H2), and temperature, using a consistent set of electrokinetic parame
Beruski O, Lopes T, Kucernak A, et al., 2016, Comparison between Darcy's law and Darcy-Brinkman formulation for reactant transport in PEFC porous media, Publisher: AMER CHEMICAL SOC, ISSN: 0065-7727
Kucernak ARJ, kakati, Unnikrishnan A, et al., 2016, Recovery of Polymer Electrolyte Fuel Cell exposed to sulfur dioxide, International Journal of Hydrogen Energy, Vol: 41, Pages: 5598-5604, ISSN: 1879-3487
Sulfur dioxide (SO2) is a common atmospheric contaminant which has a deleterious effect on fuel cells. The performance of a Polymer Electrolyte Fuel Cell (PEFC) utilising a Pt on nitrogen doped graphene support as the cathode catalyst was studied in the presence of air contaminated with known levels of SO2. The nitrogen doped graphene supported platinum was synthesized by a hydrothermal method. At levels of 25ppm SO2 in air there was within 15 minutes a 28 % reduction in the PEFC performance at 0.5 V. The performance degradation was more severe at higher SO2 concentrations. At 100 ppm SO2 in air the performance degraded by 91% at the same potential. The power loss of the fuel cell could not be recovered by externally polarising the PEFC at 1.6 V. Even after continuous potential cycling of the cell for 9 h only 80% of the initial performance could be recovered. However, a 15 minute treatment with 0.4% O3 in air showed almost a 100% performance recovery of the 100ppm SO2 contaminated fuel cell. The enhanced recovery of the fuel cell is related both to the chemical reaction of O3 with the adsorbed sulphur contaminant, and an increase of cathode potential during the electrochemical treatment.
This data is extracted from the Web of Science and reproduced under a licence from Thomson Reuters. You may not copy or re-distribute this data in whole or in part without the written consent of the Science business of Thomson Reuters.


text:
- Windows
- Office Tools
- Document management
- PDF to IMAGE
PDF to IMAGE
PDF to IMAGE 5.3 is available as a free download on our software library. Our antivirus scan shows that this download is virus free. The actual developer of the software is OakDoc Technology Inc. PDF to IMAGE lies within Office Tools, more precisely Document management.
Commonly, this program's installer has the following filenames: pdf2image.exe, PDF To Image.exe, pdf-to-image.exe, PDF2IMG.exe and PDFtoImage.exe etc. The latest version of the program can be installed on PCs running Windows XP/Vista/7/8/10, 32-bit. The most popular versions of the program 5.3, 4.1 and 2.2. The file size of the latest downloadable installation package is 1.3 MB.
From the developer:
PDF to IMAGE Converter is an easy-to-use end-user wizard for creating or manipulating image format files
PDF to IMAGE Converter supports the fast, affordable way to create professional-quality documents image format files. Its easy-to-use interface allows you to create image files by simply click the "next" button, and it offers convenient features to optimize and manipulate image files in ways that most other packages do not. It is clearly to see why it is one of the most powerful and efficient tools for your office on the market today.
You may want to check out more software, such as A-PDF To Image, ACE PDF To Image Converter or Apex PDF to Image Converter, which might be related to PDF to IMAGE.
Please add a comment explaining the reasoning behind your vote.
Office Tools
Office Tools
Editors & Converters
Remote Computing
Database Tools

subset: commoncrawl


text:
I tried, i think, all tutorials on the net. Q: This patch is gonna clone my phone? A: No it can't but it doesn't matter because you will always be current. With our unique approach to crawling we index shared files withing hours after Upload. After clicking desired file title click download now button or copy download link to browser and wait certain amount of time usually up to 30 seconds for download to begin. . Power+Volume down+home button e em seguida volume up. Do i have to flash offical firmware first and then flash custum rom? But problem remains the same.
Please read be careful because of as responsıbılıty on you. After upload, share files instantly via Social networks or via Email with your friends or family. . . As an file sharing search engine DownloadJoy finds ariza patch apk files matching your search criteria among the files that has been seen recently in uploading sites by our search spider.
If you like my hard working project consider a donation. Interestingly i have this problem while i am at home only, outside home it works but connection is not good in outside too. I did some search and concluded that i may get my original serial number back if i flash the right Stock rom. Just paste the urls you'll find below and we'll download file for you! Upload files to TraDownload with single click: How to download ariza patch apk files to my device? A: No,it's gonna bring your network back. . In next page click regular or free download and wait certain amount of time usually around 30 seconds until download button will appead. .
After 1hour, he repaired the software and now its working fine. Also, google sim reprovision and try that. If file you want to download is multipart you can use our to check whether multiple download links are still active before you start download. Everything is working fine but i hav two minor issues if some1 can help me with. . Reset Time e em seguida marque o Re-Partiton e clique em Start. Recentemente passei um aperto com o meu Galaxy S3 i9300, que depois de instalar voltar uma stock firmware para retirar o root ferrei ele, ele pegava rede porém não fazia ligações.
. . Q: How can i use it on stock rom? This error occurs when your network provider is able to retrieve your device imei number. Espero ter ajudado credito total danielratk. Escuche de un parche llamado ariza patch pero no anda, ni tampoco encontre este parche para s4 mini, conocen otro método que sea para este modelo y solucionar el error.
That is no big deal unless you need to get an update and it checks for this. After flashing, it got network problem. . . .
Registered users can also use our to download files directly from all file hosts where it was found on. I got the thing working at home with my network. Primeiramente vc terá que baixar os drivers da samsung ou instalar o Kies, em seguida você baixa o odin. . Also very important to be current for the new updates. .
If you found that any of above ariza patch apk files may have been subject to copyright protection. My question can this phone work again if I bring it to the local hackers? I bought a used galaxy s3 I9300 Unlocked. You can also share ariza patch apk or any other file with the community. I would try flashing back to 4. Download ariza patch apk files found Uploaded on TraDownload and all major free file sharing websites like 4shared.
. Thanx ariza patch i535, ariza patch para samsung s3 minii8190, change serial number gt i9300, efs v1 l9300 patch, kies for s3 gt-i9300 serial number not found, my s3 serial number become 00000000, numero de serie 00000 galaxy s3, s3 serial number 00000, samsung galaxy s3 serial number 00000, samsung galaxy serial number is 00000, samsung s3 serial number 00000, samsung s3 serial number 000000. Then, I spent about week trying to work it out. Your comments are very important for others who wants to use this patch. . If this is what was done or was your intent, we can't go any further in that line of discussion as that not legal in most countries and against forum guidelines.


text:
Invite guests to your next party in style with our selection of unique party invitations for any occasion, created exclusively for Minted by our community of independent designers. Whether you are looking for birthday party invitations, anniversary party invitations, cocktail party invitations, or.
If you're like a lot of people, you might not be too excited to attend your company holiday party this year. the one person in your department who doesn't accept the company's invitation for a nigh.
Invite your friends and family over for some seasonal spirits with our creative collection of holiday cocktail party invitations. The stunning designs and clever messages are sure to set the mood for good food, good drinks and good company.
For those not-so-silent nights, select from our exclusive holiday party templates & independent designer collections to get the celebration started right.
Don't call your holiday party a holiday party. So if you are one of the unfortunate souls who received an invitation, you might want to drop by the Chick-fil-A drive-thru before the party. I reache.
Invite guests to your next party in style with our selection of unique party invitations for any occasion, created exclusively for Minted by our community of independent designers. Whether you are looking for birthday party invitations, anniversary party invitations, cocktail party invitations, or.
For instance, when one of CribLife's clients wanted to have dinner at Richard Branson's house in London by invitation. arr.
The last thing your party plans need is a fight. For many years, anyone who was displaced, unloved, rejected or homeless f.
Christmas Holiday Invitations We feature hundreds of themes from which to choose, so finding the perfect Christmas party invitations for you and your gathering is delightfully easy. From formal dinners and cocktail parties to casual family get-togethers, we have the Christmas party invitations and the holiday party invitations to fit the.
Halloween isn't just a holiday-it's our entire October mood. Light as a Feather. No, this is not an invitation to play the.
Refugio Camping Most of the spilled oil has been cleaned up, according to officials, though crews are still scraping oil off rocks at Refugio State Beach. The beach and campground is scheduled to re-open Friday. Teams of white-clad workers used rakes, trucks and pads to scoop up thick oil covering the sand on the Refugio Beach, where
A holiday party is a good excuse to gather all the people special to you in one room and an invitation becomes an important tool for it. When Planning for the Party There are different reasons for throwing a party.
Many cities and towns, such as Mooresville, are honoring their local servicemen and women with celebrations, parades, banquet.
Bubbly Celebration Holiday Party Invitation Design 1025681 by Denise Bente Print Method: Digital Printing Card Size: 7-7/8" x 5-1/2" Design Details: This flat party invitation is digitally printed in ink. The text on the front can be customized with your choice of font style, size and color.
A birthday is the anniversary of the birth of a person, or figuratively of an institution.Birthdays of people are celebrated in numerous cultures, often with birthday gifts, birthday cards, a birthday party, or a rite of passage. Many religions celebrate the birth of their founders or religious figures with special holidays (e.g. Christmas, Mawlid, Buddha's Birthday, and Krishna Janmashtami).
Defining your party is also a matter of figuring out its level of formality. Morgan says the more formal the party, the farther in advance you should send invitations. You Can Throw a Fabulous Part.
The Oxford Union, which extended the invitation, says it will not rescind it. The AfD has risen to become the third-largest p.
The holiday invitations you send to guests will set the tone for your party, and with designs to suit every taste you are sure to find the perfect holiday party invites. Storkie's unique selection is sure to impress (and receive many compliments from friends and family).
Zip Code Of Camp Lejeune Nc So far, the names of the men have not been released. CBSNews.com reports the men had been showing off the video as a "war trophy" at their home base in Camp Lejeune in NC. At least two of the Marines. Explore the best bike trails in North Carolina using TrailLink.com. View the most authoritative North
Now that fall is here, it's time to start thinking about all the party invitations that are inevitably going to be coming your way. From weddings and nights out, to Thanksgiving and the flurry of holi.
and appreciation is an invitation to the universe to further delight you. Libra and Leo adore you. Your lucky numbers are: 4, 41, 24, 18 and 30. FORECAST FOR THE WEEK AHEAD: One can only speculate abo.
School Board member Phyllis Hope also said she attended the holiday party at the invitation of Gallagher and declared the value of the event at $500, according to a gift disclosure form she filed with.
Not only has the Mexican holiday expanded into the United States. "I guess you can call it an invitation to the spirits th.
Holiday Office Party/ Company Holiday/ Corporate Holiday Invitation Samples- these invitation designs are simple yet with a touch of corporate design, the logo of the company is present, it gives a hint that the expected people that would be coming in are.
Japan Ski Holidays Best deals for 2018/2019 ski holidays. Skiworld offers ski holidays worldwide including catered chalet holidays across Europe and North America. Great prices. Japan Skiing in Japan Ski Japan for some of the best powder skiing in the world. The Japan snow is world renowned and most of the Japan ski resorts get dumped with an
Hosting Boston's own Day of the Dead celebration was the idea of Emilio Rabasa. making "papel picado," traditional cut-pap.
Buy Littlest Pet Shop Birthday Celebration Playset: Action Figures & Statues – Amazon.com FREE DELIVERY possible on eligible purchases
Camp Rock 2 Soundtrack Song List Pop songs on soundtracks. 2 (Reprise). More than on the first album, the sequel album aims for broader demographics. Golden Earring's "Radar Love," the Village People's "Y.M.C.A.," and Joan Jett's. It's an experiment in music. rock reprise of the same tune with actor/singer/commentator Henry Rollins. Giving punk rock spins to Christmas classics might not be
A last-minute invitation to the ceremony make it so one victim's mother. The city was just starting to gear up for its eve.
READ MORE: Majority of employees don't report sexual harassment in workplace: Poll And while all of the firm's clients are still planning holiday celebrations. in as they leave and spell out in the.
Spread the word about this years office holiday party using one of our beautiful Corporate Holiday Party Invitations and get everyone in the spirit of the holidays.
Online Holiday Invitations and Greetings Online Christmas and holiday party invitations and greetings. Most with animation and holiday music. Track RSVPs, sell event tickets & upload a photo. Great for business and personal events.
If the neighbors are having a party, plan to join them. When the neighborhood sends out an invitation. to them during this.
Shop our new 2018 collection of holiday photo cards and invitations. Quickly upload your guest addresses and print your envelopes for free, or use our mailing service and let us mail your cards for you.
and holiday offerings new to the park, there's all the more reason to book your stay at the Disney Resort. Moana: A Homecomin.
Send the best free eCard for any occasion. Email funny or caring custom animated greetings or photo postcards for birthday, holiday, Valentines Day, Christmas, thank you, and special moments.
This was one holiday party where it was best to avoid the mistletoe. attended the shindig at Our Lady of Snow Hall in Brooklyn Thursday night. The invitation noted the celebration was for "adults o.
Holiday Company Parties Invitations and Christmas Company Parties Invitations are a great start to your festive occasion. A printed invitation tells your guests that they are in for a special evening.
We gratefully accepted this invitation to save the trips and time. of the day was filled with the typically loud, stimulat.
On The Beach Vacation Rentals Our Gleneden Beach vacation rentals are in a small beach community south of Lincoln City. Browse our selection of Gleneden Beach rentals. Browse Cooke Realty's Ocean Isle vacation rentals for your next beach vacation. Our Ocean Isle Beach rentals include homes, condos, luxury, and pet friendly properties. Browse Cooke Realty's Ocean Isle vacation rentals for
They were generous with their advice and provided recipes for a holiday. He says party-givers should plan a longer time period, from 7 p.m. until midnight for instance, so that their guests can acc.
Use these party invitations for both large and small events. They come in packs as small as 25 and as large as 500, giving you versatile options for your party. Ensure guests know exactly what type of party they'll be attending by using party invitations with themed designs.
Holiday party invitation (for business event) This accessible festive invitation template is perfect for a company holiday party. It features a holiday ornament set on a.