Schiller M.,Proton OnSite
Fuel Cells Bulletin | Year: 2013
With intermittent renewable energy sources frequently producing more power than the existing electricity grid can handle, the need for a complete energy storage solution is becoming more acute. Electrolysis is increasingly being seen as a scalable technology that will meet this growing demand, and so Proton OnSite is looking to commercialise MW-scale proton-exchange membrane electrolyser systems for this key application. © 2013 Elsevier Ltd.
Zou S.,Zhejiang University |
Zou S.,University of Oregon |
Burke M.S.,University of Oregon |
Kast M.G.,University of Oregon |
And 3 more authors.
Chemistry of Materials | Year: 2015
Fe cations dramatically enhance oxygen evolution reaction (OER) activity when incorporated substitutionally into Ni or Co (oxy)hydroxides, serving as possible OER active sites. Pure Fe (oxy)hydroxides, however, are typically thought to be poor OER catalysts and are not well-understood. Here, we report a systematic investigation of Fe (oxy)hydroxide OER catalysis in alkaline media. At low overpotentials of ∼350 mV, the catalyst dissolution rate is low, the activity is dramatically enhanced by an AuOx/Au substrate, and the geometric OER current density is largely independent of mass loading. At higher overpotentials of ∼450 mV, the dissolution rate is high, the activity is largely independent of substrate choice, and the geometric current density depends linearly on loading. These observations, along with previously reported in situ conductivity measurements, suggest a new model for OER catalysis on Fe (oxy)hydroxide. At low overpotentials, only the first monolayer of the electrolyte-permeable Fe (oxy)hydroxide, which is in direct contact with the conductive support, is OER-active due to electrical conductivity limitations. On Au substrates, Fe cations interact with AuOx after redox cycling, leading to enhanced intrinsic activity over FeOOH on Pt substrates. At higher overpotentials, the conductivity of Fe (oxy)hydroxide increases, leading to a larger fraction of the electrolyte-permeable catalyst film participating in catalysis. Comparing the apparent activity of the putative Fe active sites in/on different hosts/surfaces supports a possible connection between OER activity and local structure. © 2015 American Chemical Society.
Seley D.,University of Wyoming |
Ayers K.,Proton OnSite |
Parkinson B.A.,University of Wyoming
ACS Combinatorial Science | Year: 2013
A library of electrocatalysts for water electrolysis under acidic conditions was created by ink jet printing metal oxide precursors followed by pyrolysis in air to produce mixed metal oxides. The compositions were then screened in acidic electrolytes using a pH sensitive fluorescence indicator that became fluorescent due to the pH change at the electrode surface because of the release of protons from water oxidation. The most promising materials were further characterized by measuring polarization curves and Tafel slopes as anodes for water oxidation. Mixed metal oxides that perform better than the iridium oxide standard were identified. © 2013 American Chemical Society.
Dedigama I.,University College London |
Ayers K.,Proton OnSite |
Shearing P.R.,University College London |
Brett D.J.L.,University College London
International Journal of Electrochemical Science | Year: 2014
A simple electrochemical model is developed to understand the overpotentials associated with a polymer electrolyte membrane water electrolyser (PEMWE) operating at room temperature (20 °C) and atmospheric pressure (1 atm). The model is validated using experimental results and fitted parameter values are reported. © 2014 The Authors.
Choe Y.-K.,Japan National Institute of Advanced Industrial Science and Technology |
Fujimoto C.,Sandia National Laboratories |
Lee K.-S.,Los Alamos National Laboratory |
Dalton L.T.,Proton OnSite |
And 3 more authors.
Chemistry of Materials | Year: 2014
(Chemical Equation Presented) Alkaline stability of benzyl trimethylammonium (BTMA)-functionalized polyaromatic membranes was investigated by computational modeling and experimental methods. The barrier height of hydroxide initiated aryl-ether cleavage in the polymer backbone was computed to be 85.8 kJ/mol, a value lower than the nucleophilic substitution of the α-carbons on the benzylic position of BTMA cationic functional group, computed to be 90.8 kJ/mol. The barrier heights of aryl-aryl cleavage (polymer backbone) are 223.8-246.0 kJ/mol. The computational modeling study suggests that the facile aryl-ether cleavage is not only due to the electron deficiency of the aryl group but also due to the low bond dissociation energy arising from the ether substituent. Ex situ degradation studies using Fourier transform infrared (FTIR) and 1H nuclear magnetic resonance (NMR) spectroscopy indicated that 61% of the aryl-ether groups degraded after 2 h of treatment in 0.5 M NaOH at 80 °C. BTMA cationic groups degraded slowly over 48 h under the same conditions. In situ degradation studies validate the calculated results: anion exchange membrane fuel cells and water electrolyzer using poly(arylene ether) membranes exhibit a catastrophic, premature failure during lifetime tests, while no sudden performance loss is observed with an ether-free poly(phenylene) membrane. Despite the gradual performance loss due to the degradation of BTMA cation functional group, the membrane electrode assembly using the poly(phenylene) membrane exhibited a lifetime of >2000 h in the alkaline water electrolyzer mode at 50 °C. © 2014 American Chemical Society.