Composite membranes for alkaline electrolysis based on polysulfone and mineral fillers

Burnat, Dariusz; Schlupp, Meike V.F.; Wichser, Adrian; Lothenbach, Barbara; Gorbár, Michal; Züttel, Andreas; Vogt, Ulrich

doi:10.1016/j.jpowsour.2015.04.066

Cited by 65 publications

(38 citation statements)

References 29 publications

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“…[11][12][13] Significant performance improvements of the conventional technology have been demonstrated using e.g. increased temperatures, 14 novel diaphragm materials, [15][16][17][18][19] active bubble removal 20,21 or advanced electrode designs. 22 Replacing the diaphragm with an ion-conducting membrane represents a new direction in the development of advanced alkaline electrolyzers as recently discussed by Pletcher and Li.…”

mentioning

confidence: 99%

Zero-Gap Alkaline Water Electrolysis Using Ion-Solvating Polymer Electrolyte Membranes at Reduced KOH Concentrations

Kraglund

Aili

Jankova

et al. 2016

J. Electrochem. Soc.

112

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Membranes based on poly(2,2 -(m-phenylene)-5,5-bibenzimidazole) (m-PBI) can dissolve large amounts of aqueous KOH to give electrolyte systems with ion conductivity in a practically useful range. The conductivity of the membrane strongly depends on the concentration of the aqueous KOH phase, reaching about 10 −1 S cm −1 or higher in 15-25 wt% KOH. Herein, m-PBI membranes are systematically characterized with respect to performance and short-term stability as electrolyte in a zero-gap alkaline water electrolyzer at different KOH concentrations. Using plain uncatalyzed nickel foam electrodes, the cell based on m-PBI outperforms the cell based on the commercially available state-of-the-art diaphragm and reaches a current density of 1500 mA cm −2 at 2.4 V in 20 wt% KOH at 80 • C. The cell performance remained stable during two days of operation, though post analysis of the membrane using size exclusion chromatography and spectroscopy reveal evidence of oxidative degradation of the base polymer at KOH concentrations of 15 wt% and higher. Converting surplus electrical energy into hydrogen by water electrolysis represents an attractive approach to balance the electric grid when an increasing fraction of the power input originates from fluctuating renewable sources.1 Characterized by their robustness and durability, alkaline electrolyzers have been available for a long time on a commercial basis for large scale hydrogen and oxygen production through electrochemical water splitting.2,3 The alkaline environment allows for a cell construction completely free from noble metals, where the oxygen 4-6 and hydrogen 7-9 evolution reactions readily occur on nickel and other transition metal-based materials. The electrodes are separated by an aqueous solution of potassium hydroxide confined in a porous diaphragm to reduce the intermixing of the product gasses. Between the diaphragm and the electrode is an electrolyte-filled gap to facilitate gas removal. This cell design gives an interelectrode distance in the range of a few millimeters and therefore a relatively large internal resistance, 3,10 even though the specific conductivity of the aqueous potassium hydroxide electrolyte used is remarkably high. Replacing the diaphragm with an ion-conducting membrane represents a new direction in the development of advanced alkaline electrolyzers as recently discussed by Pletcher and Li. 23 It allows for a zero-gap design with an inter-electrode distance of less than 100 μm, in which the membrane is sandwiched in between two porous electrodes. One approach in this connection is to use alkaline ion exchange membranes (AEM) based on quaternary ammoniumfunctionalized polymers, [24][25][26] but improving the stability of the polymer backbone 27 as well as of the anion exchange moieties 28 are apparent challenges.An alternative approach is to use a membrane based on an aqueous electrolyte dissolved in a polymer matrix. The ion-solvating polymer electrolytes are often soluble in water, 29 but as first demonstrated by Xing and Savadogo, 30 poly(2,2...

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confidence: 99%

Zero-Gap Alkaline Water Electrolysis Using Ion-Solvating Polymer Electrolyte Membranes at Reduced KOH Concentrations

Kraglund

Aili

Jankova

et al. 2016

J. Electrochem. Soc.

112

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“…More recently, there was an increased interest in composite membranes based on polysulfone and mineral fillers. These membranes were measured to have superior performance than commercially available products with the additional advantage of allowing higher operating temperatures [21].…”

Section: Separatormentioning

confidence: 99%

An Analytical Model for the Electrolyser Performance Derived from Materials Parameters

Gallandat¹,

Romanowicz²,

Züttel³

2017

JPEE

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Hydrogen is seen as a key element for the transition from a fossil fuel based economy to a renewable, sustainable economy. Hydrogen can be used either directly as an energy carrier or as a feedstock for the reduction of CO 2 to synthetic hydrocarbons. Hydrogen can be produced by electrolysis, decomposing water in oxygen and hydrogen. This paper presents an overview of the three major electrolysis technologies: acidic (PEM), alkaline (AEL) and solid oxide electrolysis (SOEC). An updated list of existing electrolysers and commercial providers is provided. Most interestingly, the specific prices of commercial devices are also given when available. Despite tremendous development of the PEM technology in the past decades, the largest and most efficient electrolysers are still alkaline. Thus, this technology is expected to play a key role in the transition to the hydrogen society. A detailed description of the components in an alkaline electrolyser and an analytical model of the process are provided. The analytical model allows investigating the influence of the different operating parameters on the efficiency. Specifically, the effect of temperature on the electrolyte conductivity-and thus on the efficiency-is analyzed. It is found that in the typical range of operating temperatures for alkaline electrolysers of 65˚C -220˚C, the efficiency varies by up to 3.5 percentage points, increasing from 80% to 83.5% at 65˚C and 220˚C, respectively.

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“…Dissolved gases (H 2 or O 2 ) are carried by the electrolyte, and the hydrogen concentration in the anode rapidly increases to the critical point (4 mol% H 2 in O 2 ), which requires the AWE to switch off for safety during partial load operation. The limited operation behavior is mainly attributed to gas crossover via diffusion and permeation . The risk of gas crossover via electrolyte permeation through the porous separator grows rapidly for a pressurized AWE .…”

Section: Introductionmentioning

confidence: 99%

“…The limited operation behavior is mainly attributed to gas crossover via diffusion and permeation. 22,23 The risk of gas crossover via electrolyte permeation through the porous separator grows rapidly for a pressurized AWE. 24,25 Thus, it is necessary to synthesize a porous separator with reduced gas crossover in high-pressure AWE coupled with RES to minimize the wasted electricity.…”

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confidence: 99%

The synthesis of a Zirfon‐type porous separator with reduced gas crossover for alkaline electrolyzer

et al. 2019

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Summary The rapid expansion of renewable energy sources presents a great challenge to balance the electric grid due to their intermittent and volatile nature. The surplus energy generation cannot be used or sold so that it is curtailed in order to maintain the grid balance. The excess power can be converted into a gaseous energy carrier, hydrogen via power‐to‐gas technology. Alkaline water electrolysis can be operated in a dynamic mode using renewable energy sources on a large scale. However, the risk of gas crossover across a porous separator rapidly increases when the electrolyzer operates at a low partial load or at high pressure, leading to efficiency loss and a safety issue. The commercial porous separator Zirfon PERL, which is composed of 85 wt.% zirconia nanoparticles and 15 wt.% polysulfone, exhibits a satisfactory bubble point pressure performance of approximately 2.5 bar and ionic resistance of 0.3 Ω cm2. However, the Zirfon PERL separator exhibits a high hydrogen permeability value of 20 × 10−12 mol cm−1 bar−1 sec−1 due to its large average pore size of 130 nm, resulting in a limited dynamic range of the electrolyzer. Therefore, it is necessary to develop a porous separator with reduced gas crossover. In this study, we synthesize a porous ZrO2/polysulfone composite separator by varying the amount of ZrO2 (75‐85 wt.%) via the film‐casting method. The 75 wt.% ZrO2/25 wt.% polysulfone composite separator, which contains a low amount of ZrO2, shows a high bubble point pressure of 3.8 bar, a low ionic resistance of 0.3 Ω cm2, and are reduced hydrogen permeability of 4.2 × 10−12 mol cm−1 bar−1 sec−1 compared with that of Zirfon PERL separator. The enhanced performance of this separator is attributed to the reduced average pore size of around 70 nm and high surface wettability with a contact angle of 75°. This result will help alkaline electrolyzer systems be operated as more controllable loads.

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Composite membranes for alkaline electrolysis based on polysulfone and mineral fillers

Cited by 65 publications

References 29 publications

Zero-Gap Alkaline Water Electrolysis Using Ion-Solvating Polymer Electrolyte Membranes at Reduced KOH Concentrations

Zero-Gap Alkaline Water Electrolysis Using Ion-Solvating Polymer Electrolyte Membranes at Reduced KOH Concentrations

An Analytical Model for the Electrolyser Performance Derived from Materials Parameters

The synthesis of a Zirfon‐type porous separator with reduced gas crossover for alkaline electrolyzer

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