Nanostructured Electrodes

At the FAU Erlangen-Nürnberg, we will prepare, investigate and apply nanostructured electrodes with enhanced specific surface area. To this goal, we will exploit the anodization of aluminium, an industrial process, for creating structures of accurately defined and tunable porosity. The catalyst will then be deposited onto the porous structure either by atomic layer deposition (ALD) or by wet chemical methods (in particular galvanic plating). The increased surface area of the electrode will increase the current density of the vanadium-air redox flow battery, and thereby its power density.

We will first carry out a fundamental investigation of the relationship between the surface morphology of the electrode and the current density that can be reached for electrochemical reactions. This study will be carried out on planar samples, which can be used as model systems with very accurately tunable geometric parameters. The diameter and length of cylindrical pores arranged in parallel arrays will be varied systematically and the electrical current density will be measured as it depends on those parameters.

In the next step, we will develop a method for the controlled preparation of nanopores on substrates of technical relevance. The parameters of the anodization, the galvanic deposition, and the atomic layer deposition, will be modified for the application to non-planar, electrically conducting substrates such as mesh and felt. We will define the optimal parameters that enable one to reach the best possible control over the geometry (pore size and layer thickness) and the homogeneity for each sample. This optimization will be performed within the constraints determined at HAW that guarantee sufficient mass and energy transport.

Finally, we will combine the materials and procedures optimized by the other partners in order to create parts for the prototype. The best substrates obtained at the HAW Hamburg will structured with the methods developed at the FAU and coated with the best catalysts from the RWTH Aachen. Hereby, we will beware the necessary materials compatibility with the membranes (FumaTech), the extrusion procedure (Uniwell), as well as the electrolytes (University Hamburg).

Figure reproduced with permission from J. Gemmer, Y. Hinrichsen, A. Abel, J. Bachmann, J. Catal. 2012, 290, 220-224; copyright Elsevier.