Sulfur Dioxide Crossover during the Production of Hydrogen and Sulfuric Acid in a PEM Electrolyzer

Weidner, John W.

doi:10.1149/1.3129444

Cited by 23 publications

(54 citation statements)

References 15 publications

(37 reference statements)

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“…8,11,12 The data for s-PBI were collected during 18 different tests on different membranes with the temperature ranging from 70…”

Section: Resultsmentioning

confidence: 99%

“…8,9,11,12 However, an increase in acid concentration at the anode in the SDE operated with s-PBI shows no adverse effect on membrane resistance because the conductivity of s-PBI is not dependent on water to facilitate proton conduction. In addition, the measured resistance was not a function of temperature between 70…”

Section: Resultsmentioning

confidence: 99%

“…[8][9][10][11][12] For example, Westinghouse was only able to get the cell voltage down to 1.0 V at 400 mA/cm 2 , where we achieved 500 mA/cm 2 at 0.71 V and 1.2 A/cm 2 at 1.0 V using Nafion 212 (N212). However, to achieve overall process efficiency, concentrated sulfuric acid as well as low cell voltage at high current densities are * Electrochemical Society Member.…”

Section: -6mentioning

confidence: 94%

“…The resulting reactions at the anode and cathode, respectively, are: 2H + + 2e − → H 2 U 0 H2 = 0 V vs. SHE [3] Thus, the overall reaction in the electrolyzer is represented as: SO 2 + 2H 2 O → H 2 SO 4 + H 2 [4] Considerable progress was made in the last decade in lowering the operating voltage and increasing the current density of the SDE by moving from a microporous rubber diaphragm separator used by Westinghouse 7 to a perfluorinated sulfonic acid membrane (e.g., DuPont's Nafion). [8][9][10][11][12] For example, Westinghouse was only able to get the cell voltage down to 1.0 V at 400 mA/cm 2 , where we achieved 500 mA/cm 2 at 0.71 V and 1.2 A/cm 2 at 1.0 V using Nafion 212 (N212). However, to achieve overall process efficiency, concentrated sulfuric acid as well as low cell voltage at high current densities are necessary.…”

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Characterizing Voltage Losses in an SO₂Depolarized Electrolyzer Using Sulfonated Polybenzimidazole Membranes

Garrick

Wilkins

Pingitore

et al. 2017

J. Electrochem. Soc.

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The hybrid sulfur cycle has been investigated as a means to produce CO 2 -free hydrogen efficiently on a large scale through the decomposition of H 2 SO 4 to SO 2 , O 2 , and H 2 O, and then electrochemically oxidizing SO 2 back to H 2 SO 4 with the cogeneration of H 2 . The net effect is the production of hydrogen and oxygen from water. Recently, sulfonated polybenzimidazoles (s-PBI) have been investigated as a replacement for Nafion due to the ability to offer increased process efficiency through the generation of higher acid concentrations at lower potentials. Here, we measure the acid concentrations and individual potential contributions toward the overall operating voltage seen in the SO 2 -depolarized-electrolyzer. We then determine model parameters necessary to predict voltage losses in a cell over a wide range of operating temperatures, pressures, currents and reactant flow rates. The hydrogen production program at the U. S. Department of Energy is examining an array of distributed and centralized hydrogen facilities that could contribute to the hydrogen generation infrastructure.1 Thermochemical cycles are being considered for large scale, centralized facilities due to their potential for high efficiencies at low costs. These cycles involve a series of chemical reactions that result in the splitting of water at much lower temperatures (∼500-1000• C) than direct thermal dissociation (>2500 • C) and at much higher efficiencies than direct water electrolysis.2 Chemical species in these reactions are recycled resulting in the consumption of only energy and water to produce hydrogen and oxygen. Although there are hundreds of possible thermochemical cycles, the hybrid-sulfur (HyS) process is the only all-fluid, two step thermochemical cycle. 3-6The high temperature step (850-950• C) involves the decomposition of H 2 SO 4 to produce oxygen and sulfur dioxide via the following reaction:The SO 2 is separated, cooled, and sent to the SO 2 -depolarized electrolyzer (SDE). The resulting reactions at the anode and cathode, respectively, are:Thus, the overall reaction in the electrolyzer is represented as:Considerable progress was made in the last decade in lowering the operating voltage and increasing the current density of the SDE by moving from a microporous rubber diaphragm separator used by Westinghouse 7 to a perfluorinated sulfonic acid membrane (e.g., DuPont's Nafion). [8][9][10][11][12] For example, Westinghouse was only able to get the cell voltage down to 1.0 V at 400 mA/cm 2 , where we achieved 500 mA/cm 2 at 0.71 V and 1.2 A/cm 2 at 1.0 V using Nafion 212 (N212). However, to achieve overall process efficiency, concentrated sulfuric acid as well as low cell voltage at high current densities are * Electrochemical Society Member.* * Electrochemical Society Student Member. * * * Electrochemical Society Fellow.z E-mail: taylor.garrick@gm.com; weidner@cec.sc.edu necessary. The key issue when using membranes like Nafion that rely on water for their proton conductivity is that high acid concentrations dehydrate ...

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“…8,11,12 The data for s-PBI were collected during 18 different tests on different membranes with the temperature ranging from 70…”

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: -6mentioning

confidence: 94%

mentioning

confidence: 94%

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Characterizing Voltage Losses in an SO₂Depolarized Electrolyzer Using Sulfonated Polybenzimidazole Membranes

Garrick

Wilkins

Pingitore

et al. 2017

J. Electrochem. Soc.

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“…We developed a gas-fed anode electrolyzer in which SO 2 is oxidized to H 2 SO 4 via the following reaction 11,[14][15][16][17][18] …”

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Quantifying Individual Potential Contributions of the Hybrid Sulfur Electrolyzer

Staser

Gorensek

Weidner

2010

J. Electrochem. Soc.

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The hybrid sulfur cycle has been investigated as a means to produce clean hydrogen efficiently on a large scale by first decomposing H 2 SO 4 to SO 2 , O 2 , and H 2 O and then electrochemically oxidizing SO 2 back to H 2 SO 4 with the cogeneration of H 2 . Thus far, it has been determined that the total cell potential for the hybrid sulfur electrolyzer is controlled mainly by water transport in the cell. Water is required at the anode to participate in the oxidation of SO 2 to H 2 SO 4 and to hydrate the membrane. In addition, water transport to the anode influences the concentration of the sulfuric acid produced. The resulting sulfuric acid concentration at the anode influences the equilibrium potential of and the reaction kinetics for SO 2 oxidation and the average conductivity of the membrane. A final contribution to the potential loss is the diffusion of SO 2 through the sulfuric acid to the catalyst site. Here, we extend our understanding of water transport to predict the individual contributions to the total cell potential. © 2010 The Electrochemical Society. ͓DOI: 10.1149/1.3397901͔ All rights reserved. The hybrid sulfur ͑HyS͒ cycle has gained attention due to the possibility of using this process to produce clean hydrogen on a large scale at efficiencies higher than those using water electrolysis.1-19 The high temperature decomposition of H 2 SO 4 to SO 2 , O 2 , and H 2 O is suited for use with advanced gas-cooled nuclear reactor heat sources or solar receiver arrays.1-7 The electrolysis step described here is coupled with the high temperature step to complete the cycle. We developed a gas-fed anode electrolyzer in which SO 2 is oxidized to H 2 SO 4 via the following reaction 11,[14][15][16][17][18] We have successfully carried out Reactions 1 and 2 over a range of operating conditions ͑i.e., temperature, flow rate, and membrane pressure differential͒ and design variations ͑i.e., catalyst loading and membrane type and thickness͒. [14][15][16][17] We have also accurately predicted water transport and correlated the operating potential to the sulfuric acid concentration produced at the anode. [15][16][17] We have shown that the concentration of sulfuric acid produced at the anode increases with current density and that the sulfuric acid concentration at the anode influences the cell potential via the reversible cell potential U eq . 18Although we have previously correlated cell potential to acid concentration and hence water transport, a quantitative measure of the various potential losses has never been made. In this discussion, we present a comprehensive investigation of the components that make up the total cell potential ͑i.e., reversible cell potential, membrane resistance, and catalyst activity͒ to better understand and improve electrolyzer performance and operation. ExperimentalThe experimental setup was the same as that described previously.14-17 The cell was a standard 10 cm 2 cell from Fuel Cell Technologies, Inc. Reactants and products were fed to and from the cell through Kynar manifolds inst...

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SO2 carry-over and sulphur formation in a SO2-depolarized electrolyser

Santasalo-Aarnio

Virtanen

Gasik

2016

J Solid State Electrochem

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Sulfur Dioxide Crossover during the Production of Hydrogen and Sulfuric Acid in a PEM Electrolyzer

Cited by 23 publications

References 15 publications

Characterizing Voltage Losses in an SO₂Depolarized Electrolyzer Using Sulfonated Polybenzimidazole Membranes

Characterizing Voltage Losses in an SO₂Depolarized Electrolyzer Using Sulfonated Polybenzimidazole Membranes

Quantifying Individual Potential Contributions of the Hybrid Sulfur Electrolyzer

SO2 carry-over and sulphur formation in a SO2-depolarized electrolyser

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Sulfur Dioxide Crossover during the Production of Hydrogen and Sulfuric Acid in a PEM Electrolyzer

Cited by 23 publications

References 15 publications

Characterizing Voltage Losses in an SO2Depolarized Electrolyzer Using Sulfonated Polybenzimidazole Membranes

Characterizing Voltage Losses in an SO2Depolarized Electrolyzer Using Sulfonated Polybenzimidazole Membranes

Quantifying Individual Potential Contributions of the Hybrid Sulfur Electrolyzer

SO2 carry-over and sulphur formation in a SO2-depolarized electrolyser

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Characterizing Voltage Losses in an SO₂Depolarized Electrolyzer Using Sulfonated Polybenzimidazole Membranes

Characterizing Voltage Losses in an SO₂Depolarized Electrolyzer Using Sulfonated Polybenzimidazole Membranes