Alkaline water electrolysis with gas diffusion electrodes
In this project physical-chemical and electrochemical measurements with a gas diffusion electrode (GDE) are performed in order to use the GDE in a „hybrid“ alkaline water electrolysis cell.
Hydrogen will play an important role in the future energy system as an energy-carrying and -storing molecule. Hydrogen can be produced using alkaline water electrolysis (AEL) powered by excess energy. To simplify the AEL process this project works with a “hybrid” cell concept, which was used successfully in experiments of previous projects. This concept combines a hydrogen producing cathode and an oxygen producing gas diffusion electrode (GDE) as anode, which are separated by a separator within a zero-gap-assembly in a classical AEL half-cell. Hence, only one electrolyte circulation is needed, which should optimize the purity of product gases and decrease the costs.
The focus of this project lies on the nickel-iron-GDEs, characterizing them physical-chemically and electrochemically with various methods. Thus, structure-character-relations will be identified in order to develop promising GDEs for further examinations in the “hybrid” cell setup. Furthermore, the limits of operation for the “hybrid” cell setup will be determined by varying operating conditions.
To determine, whether the gas purity of the products is influenced solely by the permeability of the separator, the product gases will be examined. Using all measured data, a mathematical model will be developed to represent the interaction of the different transport processes and the electrochemical reaction in the GDE. This model will be used further to calculate the overpotential of the GDE in relation to the operating conditions. Thus, loss mechanisms will be explained and improved approaches for the GDE will be made available.