As part of this project, physico-chemical measurements are being carried out on gas diffusion electrodes in order to use them in a "hybrid" cell in alkaline water electrolysis.

Hydrogen will play a decisive role in the energy system of the future as an energy carrier and storage molecule. Alkaline water electrolysis (AEL), which can be operated with surplus energy, is suitable for the production of hydrogen. In order to simplify the AEL process, this project is working on a "hybrid" cell concept that has been used successfully in preliminary work. This concept combines a hydrogen-evolving cathode and an oxygen-evolving gas diffusion electrode (GDE) as the anode, separated by a separator in a zero-gap setup in a classic AEL half-cell. This means that only one electrolyte circuit is required, which should improve the purity of the gases formed and reduce costs.

The nickel-iron GDEs used for this purpose are the focus of this project and will be characterized physico-chemically and electrochemically using various methods. In this way, structure-property relationships are to be determined in order to provide promising GDEs for investigations in the "hybrid" cell. Furthermore, the performance limits will be determined by varying the operating conditions of the "hybrid" cell.

Further investigations of the product gases will be used to check whether the gas purity of the products is determined solely by the permeability of the separator. Using the findings from all the measurements, a mathematical model will then be developed to reflect the interaction between the various transport processes and the electrochemical reaction in the GDE. Furthermore, this model will be used to calculate the overvoltage at the GDE as a function of the operating conditions. This should clarify loss mechanisms and enable improved GDE approaches.