Today, water electrolyzers operating in the temperature range below 100 °C primarily employ proton exchange membranes as the solid electrolyte (PEMWE). In contrast to classical liquid alkaline water electrolyzers, these systems allow for higher current densities and (differential) pressure operation. However, one major drawback is their exorbitant demand for costly materials, namely titanium-based bipolar plates and iridium- and platinum-based anode catalysts, due to the acidic environment and the high potentials of the oxygen evolution reaction. Within the past decade, the technological readiness of anion exchange materials concerning hydroxide conductivity and chemical stability has been significantly boosted. These developments allow combining the advantages of membrane-based water electrolyzers with stable, low-cost materials for catalysts and porous transport media typically used in alkaline environments. However, a limitation of anion exchange membrane water electrolysis (AEMWE) is the slow hydrogen evolution kinetics in alkaline- compared to acidic media. As a possible solution, a bipolar membrane water electrolyzer (BPMWE) was postulated, which could combine the advantages of the acidic and the alkaline world: The bipolar membrane comprises an AEM layer facing the anode and a PEM layer facing the cathode. Consequently, high pH conditions at the anode could allow the replacement of costly Ir and Ti components, while the cathode could still operate under ideal conditions at low pH. Theoretically, it is expected that the bipolar membrane can establish a steady-state pH gradient across the membrane electrode assembly (MEA) by catalyzing the dissociation of water into protons and hydroxide at the bipolar interface. This thesis presents the first-time development of bipolar MEAs for water electrolysis with a liquid water feed. The most important steps can be summarized as the following: • Implementation and investigation of modular AEMWE and PEMWE building blocks for MEA operation in pure water based on ...
Investigation of Bipolar Membrane Electrode Assemblies for Water Electrolysis ; Untersuchung von bipolaren Membranelektrodeneinheiten für die Wasserelektrolyse
2021-01-01
Theses
Electronic Resource
English
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