Summary
Within the framework of the project, a holistic approach is being developed that combines both water reduction and water oxidation in one module with the aid of precious metal-free catalysts. The module consists of different functional layers which have to be coordinated with each other. The focus of the research work is the development of low-precious metal, preferably precious metal-free catalysts and their integration into an efficient overall system with separate electrode spaces, which enables the separate production of hydrogen and oxygen.
The following scientific and technical sub-goals are derived from this:
- Development of precious metal-free catalysts for water splitting
- Optimisation of a multilayer photodiode for hydrogen production
- Production and optimisation of a module for hydrogen production
- Economic and ecological consideration of the energy and environmental balance (life cycle analysis)
Results:
- Testing of different catalyst materials as coating on electrodes showed incompatibilities in the acidic pH range. Therefore the system was designed with alkaline electrolytes and an anion exchange membrane (AEM electrolysis).
- For the experiments in the specially designed demonstrator module, nickel foam coated with active material was used as electrode substrate.
- The operating point of the module was determined from separate measurements of the solar cell (power generation) and the electrolysis cell (power consumption) by superimposing the individual characteristic curves. As a result, the electrolysis can use almost 100% of the available electricity and the solar cell is the limiting component.
- The experimentally determined current density of the electrolysis operated solely by the solar cell in the final PEC system, independent of the temperatures considered, was 6.6 mA/cm² and thus corresponded to the previously determined operating points of the individual measurements. This results in a system efficiency (sunlight to hydrogen) of 8.1 % for this system.
