At Fuel Cell Research Centre innovative micro fuel cells for future application in consumer electronics (Smartphone, Internet of Things, Wearables, etc.) and independent sensor networks are developed. The innovative micro-membrane-electrode-assembly (µMEA) is based on micro structured silicon membranes which are fabricated by semiconductor and MEMS processes. This enables the integration of all components of a conventional MEA (proton conductor, current collector, catalyst layer) on an extremely thin chip. Hence, a significant reduction in volume of the micro fuel cells can be realized with thicknesses less than 1 mm which is crucial for the application in modern consumer electronics.
In a cooperative research project which was executed by ZBT and the Institute for Microelectronics Stuttgart (IMS CHIPS) and funded by the German Federal Ministry of Economic Affairs and Energy a successful proof of concept could be achieved. The silicon membranes have a minimal thickness of 5 µm at sufficient mechanical stability and without electric shortcuts. A power density of 15 mW/cm2 at room temperature and in dry conditions could be realised. As standard processes of semiconductor industry are used the active area of the membrane can be scaled corresponding to the intended application.
In order to realize fully functioning micro fuel cell systems the next steps will be the further improvement of the power density as well as to develop the additional components like a micro scaled package, a micro periphery and micro hydrogen storage. Especially the hydrogen storage can be identified as a tough challenge as pressurized gas cartridges are not suitable for micro applications. This is why methanol is an interesting alternative for micro fuel cells. Besides the advantage of its high energy density (4500 Wh/l) it offers the possibility to be stored in simple plastic cartridges. However, direct methanol fuel cells exhibit small power densities as the membranes that are used allow methanol to diffuse from the anode to the cathode side which results in significant power losses.
Therefore, a new research project was initialized by ZBT and IMS CHIPS to develop innovative µMEAs for micro DMFC based on the micro structured silicon membranes. These new µMEAs will contain an integrated, ca. 300 nm thick proton conductive oxide layer that will inhibit the diffusion of methanol. The project was started in July 2015 and will take 2, 5 years. The project is supported via AiF within the program "Förderung der Industriellen Gemeinschaftsforschung und -entwicklung (IGF)" by Bundesministerium für Wirtschaft und Technologie based on a decision of Deutscher Bundestag.
