Cost-efficient next-generation fuel cells
Fuel cell technologies based on polymer electrolyte membrane (PEM) technologies have the potential to revolutionise transport, greatly increasing fuel efficiency and cutting environmental impacts. However, costs must be reduced if they are to become viable in the market place. Nearly all current PEM fuel cells use platinum particles on porous carbon supports to catalyse both hydrogen oxidation and oxygen reduction. Except for the catalysts, work to date has barely focused on other aspects of active layers that play a crucial role in fuel cell performance. The project PEMICAN (PEM with innovative low cost core for automotive application) has brought new advancements in active layer development. PEMICAN proposed to reduce the catalyst cost down to 0.15 g of platinum per kW. To this end, it focused on increasing catalyst use and power density by improving the transport properties of active layers. This approach was combined with reducing catalyst loading by controlling its distribution to a very thin layer on the anode side and gradients on the cathode side. As such, efforts were devoted to introducing specific electrolytes and carbon black into the active layers. These new raw materials helped improve charge and gas transfers, increasing the electrical current delivered and consequently the power density. To reduce catalyst loading, partners located platinum in places where it is most useful. Tests demonstrated that high power density was difficult to reach with such a low catalyst loading target (i.e. 0.15 g/kW). In the future, the priority will be to increase the power density up to ideally 1 W per square metre, even if higher catalyst loadings are necessary for this. Partners only managed to decrease platinum loading from 1 to 0.57 g per platinum. Another achievement was the development of a pore network model of the cathode catalyst layer. Simulations showed that non-uniform electrodes have a positive impact on PEM fuel cell performance, while the thinner the electrode the more efficient the platinum catalyst will be. Project findings will contribute to decreasing PEM fuel cell costs, thus enabling mass market development for automotive application. While the focus was on pure platinum, project results should also be useful in the case of non-pure platinum, which offers further cost reductions.
Keywords
Fuel cells, platinum, polymer electrolyte membrane, active layers, automotive, power density
