The need to regularly recharge batteries in portables with terminals may become a thing of the past. An STMicroelectronics-led project aims to create micro fuel cells, which are small enough to fit inside a mobile handset. Such cells will generate all the electricity needed for power by using cheap, clean, and readily available organic fuels.
Most fuel cell research has focused on high-power automotive systems. This joint research project with the University of Naples, though, is investigating replacing the rechargeable batteries used in mobile phones with tiny fuel cells that can be refilled whenever needed, just like refillable lighters. The use of fuel cells instead of batteries would reduce the weight of mobile devices and make "recharging" much more convenient because the cells could be simply refilled with fuel whenever necessary.
The main challenge of applying fuel cell concepts to mobile phones, explains Salvo Coffa, leader of ST's Corporate Technology R&D team, is that the power source must be able to deliver around 300 mA at 3.6 V, and it must not occupy more than about 12 cm3. The output current of a fuel cell is directly related to the common surface area between the electrodes and the membrane. So, standard fuel-cell structures would require a surface area of about 60 cm2 to deliver 300 mA, which is much larger than the area available in a mobile phone.
To overcome that limit, ST's 3D fuel cell structures' thousands of buried microchannels maximize the contact area between the gases, the catalysts, and the electrodes (see the figure). ST has also fabricated a nanoporous layer made from a layer of silicon that contains millions of pores, each just a few nanometers in diameter. The small pore sizes give the layer a very large effective surface area, increasing the efficiency of the catalysis.
Part of the research focuses on developing novel membranes that exhibit high proton conductivity and lower cost compared to the membrane materials that are commercially available today.
Although there is still further work to do before these developments can be integrated into a commercial technology, ST is very optimistic about their potential. This project is partially funded by the National Research Project, which seeks to develop small fuel cells for portable electronic applications. Partially funded by the Italian government, the National Research Project includes CNR-IMM, CNR-ITAE, CNR-ITS, and Pirelli labs, also of Italy. For more details, go to www.st.com.