Production of Energy from High Performance, Platinum-Free Fuel Cells
Thanks to innovative anode electrocatalysts based on nanostructured palladium, the first entirely platinum-free fuel cells have been created that release a power density greater than 500 mW cm-2. Their use could revive hydrogen technology for cars and portable energy generators with “zero emissions” of pollutants. The research was coordinated by ICCOM-Cnr of Florence.
A fuel cell is a device capable of directly transforming the chemical energy contained in a fuel (in this case hydrogen) directly into electricity and only water as waste material. One of the biggest obstacles to the large-scale deployment of “zero emission” fuel cells of pollutants is their high cost. Recent analyzes have shown that 45% of the cost is due to the platinum electrocatalyst (about $ 49 / kW). Platinum is a very expensive metal, scarcely available in nature and it would not be enough for all cars on the road if they were equipped with hydrogen fuel cells. The complete removal of platinum from fuel cells, and its replacement with cheaper and more abundant metals in nature, has been attempted with little success.
An alternative to platinum-based Proton Exchange Membrane Fuel Cells (PEM-FC), which operate in highly corrosive acidic conditions, could be represented by anion exchange membrane fuel cells (AEM-FC), but so far attempts to making high-performance platinum-free cells have had little success. In fact, due to the slow oxidation kinetics of hydrogen in a basic environment, only a few tens of mWcm-2 were obtained. This power is too low when compared to commercial hydrogen car cells and platinum-based portable systems that release up to 800mW cm-2.
A study conducted at ICCOM-Cnr in Florence by a team coordinated by Francesco Vizza and Hamish Miller, in collaboration with the Institute of Technology of Haifa (Israel), the Israeli company CellEra, IOM-Cnr, ISTM- Cnr, the European Synchrotron Radiation Facility of Grenoble and the University of Florence, showed that platinum-free fuel cells can release power densities greater than 500 mW cm-2. The research result was published in Angewandte Chemie International Edition (DOI: 10.1002 / anie.201600647). The authors found that an anode electrode, consisting of palladium nanoparticles supported on a composite of Vulcan XC-72 and cerium oxide (CeO2), exhibits a high oxidation kinetics of hydrogen in an alkaline environment. The structure of the catalyst, which allows the intimate contact of palladium with ceria, favors the breaking of the hydrogen-hydrogen bond and the insertion of hydroxyl ions on the palladium, accelerating the electron release process and therefore the production of electric current in the fuel cell.