Performance of the Polymer Electrolyte Alkaline Water Electrolyser Stack utilizing Diluted KOH Solutions.

Kód výsledku v IS VaVaI

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Výsledek na webu

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DOI - Digital Object Identifier

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Jazyk výsledku

angličtina

Název v původním jazyce

Performance of the Polymer Electrolyte Alkaline Water Electrolyser Stack utilizing Diluted KOH Solutions.

Popis výsledku v původním jazyce

Increasing share of the renewable sources of electricity increases the necessity of the stabilization of their output. This is due to the strong dependence of the most widely used sources i.e. sun and wind energy, both on the seasonal as well as on the actual weather conditions. One of the promising technologies enabling the balancing of the electricity distribution grid with significant amount of connected renewable sources represents water electrolysis. It is based on the decomposing of water molecules into the molecules of oxygen and hydrogen by corresponding amount of an electric work. The hydrogen is considered as an excellent energy vector. It is due to its reactivity, high energy of the chemical bond with oxygen and versatility of its further utilization. Its production by water electrolysis is connected with the electricity consumption while the reaction with oxygen in fuel cell allows the electricity recuperation. Nowadays, three main technologies of water electrolysis are under research and development. These are high temperature water electrolysis, PEM water electrolysis and alkaline water electrolysis. High temperature water electrolysis offers the advantage of the high production capacity and high efficiency, but solves the problems of material’s stability. PEM water electrolysis utilizes the proton exchange membrane as separator of the anode and cathode compartment, achieving the high flexibility, good efficiency and reasonable production intensity, however the need of the platinum metals utilizing as electrocatalysts results in high capital cost. Alkaline water electrolysis is well-established in industry due to its reliability and robustness, but it has not been significantly improved for decades. Drawbacks of this technology lay mainly in the limited flexibility. The utilization of the polymer anion selective membrane as a separator of the electrodes compartments similarly to the PEM technology can into the significant degree eliminate both of the mentioned drawbacks. This is mainly connected with reduction of the distance between the electrodes (nowadays typically in the range of tens of millimeters) to the thickness of the polymer membrane and of the concentration of liquid electrolyte (nowadays potassium hydroxide (KOH) 25-30wt.%). The aim of this work is to evaluate the influence of the liquid electrolyte concentration on the performance of the laboratory scale polymer electrolyte bipolar alkaline water electrolyser (PEAWE) stack consisting of three cells including the evaluation of the current and energy efficiency. The commonly available materials are used for the stack construction. Distribution plates are made of polyvinylchloride (PVC), the electrodes of geometrical area 78 cm2 are made from Nickel foam and bipolar as well as terminal electrodes from Ni sheets. As the separator of the electrodes compartments the chloromethylated block copolymer of styrene-ethylene-buthylene-styrene (PSEBS-CM) carrying the functional groups of 1,4-diazabicyclo[2.2.2]octane (DABCO) is used. The average thickness of the fully swollen PSEBS-CM-DABCO membrane is approximately 0.18 mm. The Ni foam electrodes are pressed directly to the surface of the membrane. The liquid electrolyte of the 1, 5, 10 and 15 wt.% KOH is used as circulation media to evaluate the influence of the KOH concentration on the current efficiency and performance of the laboratory scale PEAWE stack. The higher concentration of the liquid electrolyte improves the performance of the alkaline water electrolysis due to the improved contact in the bulk of the porous Ni foam electrodes. On the other hand, the higher concentration increases the conductivity of the pathway for the parasitic current decreasing thus the current efficiency. Using the anion selective polymer membrane as the separator of the electrode compartments it was possible to achieve the performance of the industrial technology using even the KOH solutions with reduced concentration and lower temperature.

Název v anglickém jazyce

Performance of the Polymer Electrolyte Alkaline Water Electrolyser Stack utilizing Diluted KOH Solutions.

Popis výsledku anglicky

Increasing share of the renewable sources of electricity increases the necessity of the stabilization of their output. This is due to the strong dependence of the most widely used sources i.e. sun and wind energy, both on the seasonal as well as on the actual weather conditions. One of the promising technologies enabling the balancing of the electricity distribution grid with significant amount of connected renewable sources represents water electrolysis. It is based on the decomposing of water molecules into the molecules of oxygen and hydrogen by corresponding amount of an electric work. The hydrogen is considered as an excellent energy vector. It is due to its reactivity, high energy of the chemical bond with oxygen and versatility of its further utilization. Its production by water electrolysis is connected with the electricity consumption while the reaction with oxygen in fuel cell allows the electricity recuperation. Nowadays, three main technologies of water electrolysis are under research and development. These are high temperature water electrolysis, PEM water electrolysis and alkaline water electrolysis. High temperature water electrolysis offers the advantage of the high production capacity and high efficiency, but solves the problems of material’s stability. PEM water electrolysis utilizes the proton exchange membrane as separator of the anode and cathode compartment, achieving the high flexibility, good efficiency and reasonable production intensity, however the need of the platinum metals utilizing as electrocatalysts results in high capital cost. Alkaline water electrolysis is well-established in industry due to its reliability and robustness, but it has not been significantly improved for decades. Drawbacks of this technology lay mainly in the limited flexibility. The utilization of the polymer anion selective membrane as a separator of the electrodes compartments similarly to the PEM technology can into the significant degree eliminate both of the mentioned drawbacks. This is mainly connected with reduction of the distance between the electrodes (nowadays typically in the range of tens of millimeters) to the thickness of the polymer membrane and of the concentration of liquid electrolyte (nowadays potassium hydroxide (KOH) 25-30wt.%). The aim of this work is to evaluate the influence of the liquid electrolyte concentration on the performance of the laboratory scale polymer electrolyte bipolar alkaline water electrolyser (PEAWE) stack consisting of three cells including the evaluation of the current and energy efficiency. The commonly available materials are used for the stack construction. Distribution plates are made of polyvinylchloride (PVC), the electrodes of geometrical area 78 cm2 are made from Nickel foam and bipolar as well as terminal electrodes from Ni sheets. As the separator of the electrodes compartments the chloromethylated block copolymer of styrene-ethylene-buthylene-styrene (PSEBS-CM) carrying the functional groups of 1,4-diazabicyclo[2.2.2]octane (DABCO) is used. The average thickness of the fully swollen PSEBS-CM-DABCO membrane is approximately 0.18 mm. The Ni foam electrodes are pressed directly to the surface of the membrane. The liquid electrolyte of the 1, 5, 10 and 15 wt.% KOH is used as circulation media to evaluate the influence of the KOH concentration on the current efficiency and performance of the laboratory scale PEAWE stack. The higher concentration of the liquid electrolyte improves the performance of the alkaline water electrolysis due to the improved contact in the bulk of the porous Ni foam electrodes. On the other hand, the higher concentration increases the conductivity of the pathway for the parasitic current decreasing thus the current efficiency. Using the anion selective polymer membrane as the separator of the electrode compartments it was possible to achieve the performance of the industrial technology using even the KOH solutions with reduced concentration and lower temperature.

Druh

O - Ostatní výsledky

CEP obor

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OECD FORD obor

10404 - Polymer science

Projekt

<a href="/cs/project/FV10529" target="_blank" >FV10529: Pokročilá elektrolytická výroba vodíku z OZE</a><br>

Návaznosti

P - Projekt vyzkumu a vyvoje financovany z verejnych zdroju (s odkazem do CEP)

Rok uplatnění

2019

Kód důvěrnosti údajů

S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů