Hierarchical Titanium Nitride Nanostructures As Catalyst Scaffold for PEMFC Technology

Tuesday, 3 October 2017: 09:00
National Harbor 14 (Gaylord National Resort and Convention Center)
A. Perego (Center for Nano Science and Technology@PoliMi, Politecnico di Milano, Department of Energy), G. Giuffredi (Center for Nano Science and Technology@PoliMi), A. Casalegno (Politecnico di Milano, Department of Energy), and F. DiFonzo (Center for Nano Science and Technology@PoliMi)
To overcome the high cost of the catalyst in Direct Methanol Fuel Cell (DMFC) technology, research is moving towards the reduction in the Pt loading in the electrodes by increasing the electrochemical surface area. To date, the state of the art of catalyst supports is dominated by mesoporous carbon. It shows high conductivity but suffer from stability issues especially on long term operation. As shown in the literature, titanium nitride (TiN) has a metal-like conductivity with an outstanding chemical stability [1], and moreover, it is reported to be functional towards the oxidation of adsorbate CO on platinum active sites [2].

In this contribution, we report about TiN catalysts support with self-assembled, hierarchical mesoporous nanostructure, grown by Pulsed Laser Deposition. This approach controls the gas dynamics of the nanoclusters-inseminated supersonic jet to differentiate the resulting impaction deposition, affecting the growth of the film. Platinum is deposited by means of pulsed electrodeposition and it shows a peculiar lamellar structure, most likely due to the strong electric field on the nanostructures.

Electrochemical and physical characterization are performed, showing performances towards both methanol oxidation and oxygen reduction, and revealing information about the interaction between catalyst, scaffold and reactants.

We demonstrate that it is possible to obtain a catalyst support with large surface area whose morphology can be controlled at the nanoscale. Such as a support could be ideal for the highest platinum utilization, and for the metal loading reduction, since it has similar effects with respect to the metallic Ru in commercial DMFC catalysts with a much lower cost. Stability at high potential is also investigated, and so is the possibility to use the same material as a cathode exploiting the stability of the TiN.

These results show the potential of a PVD based technique that opens the doors of the nanoscale to the fabrication of high performing electrodes whose morphological and electrical properties are easily tuned. This approach holds promises for a consistent reduction in the metal loading in DMFC technology.

[1] M. Wittmer, B.Studer and H.Melchior, Journal of Applied Physics, 52, 5722 (1981)

[2] M. Roca-Ayats, G. Garcia, J.L. Galante, M.A. Peña and M.V. Martinez-Huerta, Journal of Physical Chemistry C 117, 20769-20777 (2013)