Electrolyzer Anodes Research Articles

Steps Towards Reactive Hydrogen Pumping

Polymer electrolyte membrane (PEM) fuel cells are an attractive energy conversion device because of the potential for extremely high efficiency and low emissions. Pure hydrogen is an ideal fuel for PEM fuel cells but it is energy intensive to produce. Currently, the main method of producing hydrogen is steam reforming of natural gas. This is a break from the renewable energy future promised by hydrogen fuel cells. A greener approach to producing hydrogen is electrochemical reforming, the most obvious feedstock is water. Water electrolysis occurs at a relatively high potential (1.23 V), which makes it expensive both in terms of materials required and electricity. To fulfill the promise of fuel cells, more efficient methods of producing hydrogen must be found. One way to reduce the energy required is to depolarize the PEM electrolyzer anode by using an alternate feed. This feed must have a lower oxidation potential than water and be generated renewably. Two alternative feeds we have looked at are methanol and phosphomolybdic acid. Oxidation of methanol-water solutions to hydrogen takes place at a theoretical voltage of 0.03 V. Methanol fuel cells are a well-studied problem and the issues are known. The main issue is crossover of methanol to the cathode, lowering the total cell potential. We looked to see if this would be as problematic in a hydrogen pumping environment since there would be no oxygen at the cathode for the methanol to react with. The other feed we examined was phosphomolybdic acid (PMA). PMA is a keggin ion which is readily reduced by biomass substrates in the presence of sunlight or heat.1Our idea was to apply the concept of a depolarized anode electrolyzer to a mediated electrochemical system. This system has the PMA in solution as a combination catalyst and charge carrier. The PMA is reduced by biomass and circulated to an anode where it is oxidized to release the hydrogen removed from the biomass. This gives many of the advantages of a flow battery, where power and capacity scale separately. Our focus has been on studying the anode performance characteristics of PMA. References. 1. Liu W, Mu W, Liu M, Zhang X, Cai H, Deng Y. Solar-induced direct biomass-to-electricity hybrid fuel cell using polyoxometalates as photocatalyst and charge carrier. Nat Commun. 2014;5:3208. doi:10.1038/ncomms4208.

Oxide‐Supported IrNiOx Core–Shell Particles as Efficient, Cost‐Effective, and Stable Catalysts for Electrochemical Water Splitting

AbstractActive and highly stable oxide‐supported IrNiOx core–shell catalysts for electrochemical water splitting are presented. IrNix@IrOx nanoparticles supported on high‐surface‐area mesoporous antimony‐doped tin oxide (IrNiOx /Meso‐ATO) were synthesized from bimetallic IrNix precursor alloys (PA‐IrNix /Meso‐ATO) using electrochemical Ni leaching and concomitant Ir oxidation. Special emphasis was placed on Ni/NiO surface segregation under thermal treatment of the PA‐IrNix /Meso‐ATO as well as on the surface chemical state of the particle/oxide support interface. Combining a wide array of characterization methods, we uncovered the detrimental effect of segregated NiO phases on the water splitting activity of core–shell particles. The core–shell IrNiOx /Meso‐ATO catalyst displayed high water‐splitting activity and unprecedented stability in acidic electrolyte providing substantial progress in the development of PEM electrolyzer anode catalysts with drastically reduced Ir loading and significantly enhanced durability.

Oxide-supported IrNiO(x) core-shell particles as efficient, cost-effective, and stable catalysts for electrochemical water splitting.

Active and highly stable oxide-supported IrNiO(x) core-shell catalysts for electrochemical water splitting are presented. IrNi(x)@IrO(x) nanoparticles supported on high-surface-area mesoporous antimony-doped tin oxide (IrNiO(x)/Meso-ATO) were synthesized from bimetallic IrNi(x) precursor alloys (PA-IrNi(x) /Meso-ATO) using electrochemical Ni leaching and concomitant Ir oxidation. Special emphasis was placed on Ni/NiO surface segregation under thermal treatment of the PA-IrNi(x)/Meso-ATO as well as on the surface chemical state of the particle/oxide support interface. Combining a wide array of characterization methods, we uncovered the detrimental effect of segregated NiO phases on the water splitting activity of core-shell particles. The core-shell IrNiO(x)/Meso-ATO catalyst displayed high water-splitting activity and unprecedented stability in acidic electrolyte providing substantial progress in the development of PEM electrolyzer anode catalysts with drastically reduced Ir loading and significantly enhanced durability.

Iridium As Catalyst and Cocatalyst for Oxygen Evolution/Reduction in Acidic Polymer Electrolyte Membrane Electrolyzers and Fuel Cells

Among noble metal electrocatalysts, only iridium presents high activity for both the oxygen reduction reaction (ORR) in acid medium, in the oxide form, and the oxygen evolution reaction (OER) in acid medium, alloyed with first row transition metals. Indeed, platinum, the best catalyst for the ORR, has poor activity for the OER in any form, and ruthenium, the best catalyst for the OER, in the oxide form, possess poor activity for the ORR in any form. In this work, an overview of the application of Ir and Ir-containing catalysts for the OER in proton-exchange membrane water electrolyzer anodes, for the ORR in proton exchange membrane fuel cell cathodes, and for both OER and ORR in unit regenerative fuel cell oxygen electrodes is presented.

Initial Performance and Durability of Ultra-Low Loaded NSTF Electrodes for PEM Electrolyzers

Water based electrolyzers offer a promising approach for generating hydrogen gas for renewable energy storage. 3M's nanostructured thin film (NSTF) catalyst technology platform has been shown to significantly reduce many of the performance, cost and durability barriers standing in the way of H2/air PEM fuel cells for vehicles. In this paper we describe results from the first evaluations of low loaded NSTF catalysts in H2/O2 electrolyzers at Proton OnSite and Giner, Inc. Over two dozen membrane electrode assemblies comprising nine different NSTF catalyst types were tested in 11 short stack durability tests at Proton OnSite and 14 performance tests in 50 cm2 single cells at Giner Electrochemical Systems. NSTF catalyst alloys of Pt68Co29Mn3, Pt50Ir50 and Pt50Ir25Ru25, with Pt loadings in the range of 0.1 to 0.2 mg/cm2, were investigated for beginning-of-life performance and durability up to 4000 hours as both electrolyzer cathodes and anodes. Catalyst composition, deposition and process conditions were found to be important for meeting the performance of standard PGM blacks on electrolyzer anodes while using only 10% as much PGM catalyst. Analyses of MEA's after the durability tests by multiple techniques document changes in catalyst alloy composition, loading, crystallite structure and support stability.

A multiscale physical model for the transient analysis of PEM water electrolyzer anodes

Polymer electrolyte membrane water electrolyzers (PEMWEs) are electrochemical devices that can be used for the production of hydrogen. In a PEMWE the anode is the most complex electrode to study due to the high overpotential of the oxygen evolution reaction (OER), not widely understood. A physical bottom-up multi-scale transient model describing the operation of a PEMWE anode is proposed here. This model includes a detailed description of the elementary OER kinetics in the anode, a description of the non-equilibrium behavior of the nanoscale catalyst-electrolyte interface, and a microstructural-resolved description of the transport of charges and O(2) at the micro and mesoscales along the whole anode. The impact of different catalyst materials on the performance of the PEMWE anode, and a study of sensitivity to the operation conditions are evaluated from numerical simulations and the results are discussed in comparison with experimental data.

Effect of Firing Furnace Condition on Fired Anode Quality

Firing of aluminum electrolyzer anodes in multichamber furnaces of the open type is considered. On the basis of studying the thermal work of a firing furnace the main defects of furnace lining that arise during operation and the reasons for their development are studied. The effect of furnace construction on production of finished components from the point of view of quality, productivity, and correspondingly economic efficiency, is analyzed in detail.

A Comparison of LSM, LSF, and LSCo for Solid Oxide Electrolyzer Anodes

Composite electrodes of yttria-stabilized zirconia (YSZ) with (LSM), (LSF), and (LSCo) were prepared and tested as solid oxide electrolyzer (SOE) anodes and solid oxide fuel cell (SOFC) cathodes at , using cells with a YSZ electrolyte and a Co-ceria-YSZ counter electrode. The LSM-YSZ electrode was activated by cathodic polarization but the enhanced performance was found to be unstable during electrolysis, with the electrode impedance increasing to near its unenhanced state after . LSF-YSZ and LSCo-YSZ electrodes exhibited a nearly constant impedance, independent of current density, during both SOE and SOFC operation. The performance of an LSF-YSZ composite for electrolysis current densities above was unaffected by changing the partial pressure from , while the lower pressure harmed the performance of the LSCo-YSZ composite. The implications of these results for the characterization and optimization of SOE anodes is discussed.