Fuel Cells for Sustainable Mobility

Presently, a significant proportion of greenhouse gas emissions are caused by road traffic. Consequently, in order to achieve the climate targets, cars and trucks must forgo fossil fuels and switch to electric power. The electricity required can be provided either by batteries or by on-board hydrogen which is converted into electricity in so-called fuel cells. The only waste product is pure water, i.e. no carbon dioxide, nitrogen oxides or particulate matter. The advantage of fuel cells in buses, trucks and cars, as opposed to batteries, is that vehicles can be refuelled with hydrogen very quickly, as is currently the case with petrol. This eliminates long waiting periods while a battery is being recharged. The high energy density of hydrogen enables vehicles to achieve long ranges. A new value chain in the field of hydrogen and fuel cells, to which researchers from the Zurich University of Applied Sciences ZHAW are also contributing, is currently emerging worldwide.

Micropores within the cell

More specifically, the researchers have studied so-called polymer electrolyte fuel cells (PEFC). In these fuel cells, the reaction components, oxygen and hydrogen, must diffuse through a porous gas diffusion layer. However, at high specific performance, measured by weight, considerable electrical voltage is lost during transport of the reaction components. In order to reveal the conditions under which this happens, the researchers screened the gas diffusion layers of fuel cells using X-ray tomography, an imaging process that enables the visualization of minute structures. This allowed them to establish a connection between transportability and properties such as pore distribution, the resistance of narrow pores to transport processes, and non-circular pores. In doing so, they were able to quantify the transportability of different gas diffusion layers. The scientists then compared the X-ray measurements with computer simulations and developed mathematical models that allow fuel cell developers to build more efficient devices. One possible application is the development of new materials with optimized pore designs for gas diffusion layers. The researchers are now in the process of setting up a web platform to market the computer models, so that, in the future, all can benefit from this research work.