175 results found
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
© 2019 Elsevier B.V. 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, Pages: 357-363, ISSN: 0021-9517
© 2019 Elsevier Inc. 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.
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 A, 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
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
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 CM, Kucernak AR, 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: 2050-7488
Beruski O, Lopes T, Kucernak ARJ, et al., 2017, Investigation of convective transport in the gas diffusion layer used in polymer electrolyte fuel cells, PHYSICAL REVIEW FLUIDS, Vol: 2, ISSN: 2469-990X
Malko D, Kucernak A, 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
Cousens NEA, Kucernak ARJ, 2017, Reversible ultralow-voltage liquid-liquid electrowetting without a dielectric layer, FARADAY DISCUSSIONS, Vol: 199, Pages: 63-73, ISSN: 1359-6640
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
Chakrabarti B, Nir D, Yufit V, et al., 2017, Performance Enhancement of Reduced Graphene Oxide-Modified Carbon Electrodes for Vanadium Redox-Flow Systems, CHEMELECTROCHEM, Vol: 4, Pages: 194-200, ISSN: 2196-0216
Kakati BK, Kucernak ARJ, 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: 0013-4686
Malko D, Kucernak A, Lopes T, 2016, Performance of Fe-N/C Oxygen Reduction Electrocatalysts toward NO2-, 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: 0002-7863
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
Lopes T, Kucernak A, Malko D, et al., 2016, Mechanistic Insights into the Oxygen Reduction Reaction on Metal-N-C Electrocatalysts under Fuel Cell Conditions, CHEMELECTROCHEM, Vol: 3, Pages: 1580-1590, ISSN: 2196-0216
Malko D, Lopes T, Ticianelli EA, 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
Kucernak AR, Zalitis C, 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: 1932-7447
Kakati BK, Unnikrishnan A, Rajalakshmi N, et al., 2016, Recovery of Polymer Electrolyte Fuel Cell exposed to sulphur dioxide, INTERNATIONAL JOURNAL OF HYDROGEN ENERGY, Vol: 41, Pages: 5598-5604, ISSN: 0360-3199
Kucernak ARJ, Fahy KF, Sundaram VNN, 2016, Facile synthesis of palladium phosphide electrocatalysts and their activity for the hydrogen oxidation, hydrogen evolutions, oxygen reduction and formic acid oxidation reactions, CATALYSIS TODAY, Vol: 262, Pages: 48-56, ISSN: 0920-5861
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
Edel JB, Kornyshev AA, Kucernak AR, et al., 2016, Fundamentals and applications of self-assembled plasmonic nanoparticles at interfaces, CHEMICAL SOCIETY REVIEWS, Vol: 45, Pages: 1581-1596, ISSN: 0306-0012
Velleman L, Sikdar D, Turek VA, et al., 2016, Tuneable 2D self-assembly of plasmonic nanoparticles at liquid| liquid interfaces, NANOSCALE, Vol: 8, Pages: 19229-19241, ISSN: 2040-3364
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