NACORR - New alloy catalysts for the oxygen reduction reaction in proton exchange membrane fuel cells.
Proton Exchange Membrane Fuel Cells (PEMFC’s) could play an important role in a future society based on sustainable energy, both for averaging electric energy and in the transport sector. The biggest single loss in the PEMFC is due to the slow kinetics of the Oxygen Reduction Reaction (ORR), leading to an energy loss of roughly 35%. This results in decreased efficiency and an excessive usage of Pt, which is both scarce and expensive. Substantial efforts over the last two decades have been dedicated to reduce the Pt loading in fuel cells. Some success has been obtained in improving the ORR activity by alloying it with other late 3d transition elements such as Ni, Co, or Cu. Unfortunately, the aforementioned alloys are challenging to stabilise, as the solute metal tends to dissolve with time, ultimately leaving behind pure Pt nanoparticles. This low stability is at least partially due to the negligible alloying energy of Pt and late transition metal alloys. On the contrary, early transition metals form very stable alloys with Pt, and could potentially alleviate this problem. We therefore initiated a study of such alloys with the composition PtxM, where x >3 and M=Sc, Y, La, and Gd. It turns out that they catalyse oxygen reduction at least as well as the previously known [albeit unstable] Pt alloys. In this project, we propose to further explore this new class of materials for which we now hold two patents. We would like to develop new stable alloy catalysts by screening using density functional theory (DFT) calculations, synthesise them as both bulk materials and as nanoparticles, and test them in PEMFC’s in collaboration with two SME’s. The objective of this project is to find new and more efficient catalysts for the ORR on the cathode of the PEMFC enabling the Fuel Cell technology. The catalysts must be an order more active than pure Pt per mass and as stable against corrosion under the fuel cell operating conditions, i.e. pH=0. Two routes could be followed here: either completely replace Pt with another non-noble ORR catalyst or increase the activity of Pt containing alloys substantially and at the same time reduce the usage of Pt. Due to corrosion we shall pursue the latter - further exploring our recent success where we have shown that Pt alloyed with metals such as Sc, Y, La, Gd, and Sm offer very active catalysts for ORR.1-5 Our objective is to fully understand the exact mechanism for their activity and stability. We would capitalise on this knowledge to produce even better catalysts including e.g. alloys of Pt and inexpensive alkali earth metals. A particularly important objective is to pursue the synthesis and production of these alloys in the form of nanoparticles, since they offer the optimal activity per mass, which is the critical parameter for fuel cells. Thus our objective is to find a route for synthesising the most active alloy and stable nanoparticles for fuel cells by an economically viable route. Our ultimate goal would be to establish a spin-off company based on this technology.
Henrik Grönbeck (contact)
Full Professor at Chalmers, Physics, Chemical Physics
Technical University of Denmark (DTU)
Ministry of Higher Education and Science, Denmark
Funding Chalmers participation during 2013–2017
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