Alkaline water electrolysis with gas-diffusion electrodes

• Applicant: Professor Dr.-Ing. Thomas Turek
• Subject Area: Chemical and Thermal Process Engineering ; Technical Chemistry
• Term: since 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 450621348

In the proposed project, an experimental and theoretical study on the use of gas-diffusion electrodes (GDE) for alkaline water electrolysis in a novel „hybrid“ cell configuration in combination with a classical gas evolving electrode shall be conducted. Main emphasis is placed on the use of the GDE for oxygen evolution, since this configuration was already successfully demonstrated in previous work. Additionally, GDE shall be also employed for hydrogen evolution. First, a series of GDE with nickel and iron as electro-catalysts will be prepared and characterized with physico-chemical methods in order to achieve a broad variation of composition and pore system properties of the GDE. Subsequently, the GDE are tested in a special cell, that allows to determine the overvoltage at the GDE as a function of current density at different process conditions (temperature, electrolyte concentration, differential pressure between electrolyte and gas as well as contact pressure of the separator electrode assembly. In this way, structure-property relationships shall be determined and the most promising electrodes for the following investigations can be selected. On important goal of these further measurements is the determination of the performance limit of the newly developed cell configuration as a function of process conditions and GDE properties. Furthermore, quantitative information on the purity of the evolving oxygen shall gathered in order to test the hypothesis that the gas purity is mainly determined by the permeability of the separator and significantly higher than in the case of mixed electrolyte cycles in a classical cell. Moreover, measurements with a longer duration will deliver information about the crossover of electrolyte and condensate through the GDE as well as about the GDE stability. In an exploratory work package, the GDE will be also used as cathode in order to investigate the differences resulting from the stronger hydrogen gas evolution. Parallel to the experimental work packages, a mathematical modell will be developed with which the interaction between electrochemical reaction and the different transport processe in the GDE can be described and the overvoltage as a function of the process conditions can be calculated. In this way can the main loss mechanisms be clarified and model-based approaches for improved GDE can be developed.

• DFG Programme: Research Grants