CBE Seminar (ZOOM): Advanced Platinum-based Electrocatalysts for Proton Exchange Membrane Fuel Cell

Abstract: Platinum-based electrocatalysts are one of the most promising options as cathode electrocatalysts for proton exchange membrane fuel cells. This results from the near-to-optimal binding strength of the oxygen intermediates on Pt-surfaces, thus greatly facilitating the oxygen reduction reaction – which takes place at the said cathode. However, platinum is expensive. Platinum is scarce. Thus, platinum-based electrocatalyst activity still requires further improvements, which can be achieved through several pathways such as (i) alloying platinum with 3D transition metals or rare earth elements; (ii) designing nanomaterials with given morphologies to expose platinum facets with an optimal oxygen intermediate binding energy (e.g. (111) for Pt3Ni) or (iii) implementing, in the electrocatalyst structure, structural disorder that can locally increase the electrocatalyst activity. Those pathways lead to a new generation of advanced Pt-based electrocatalysts, including platinum-nickel octahedra, nanoframes or hollow nanostructures.

An illustration of the different approaches undertaken to improve the activity of platinum for the oxygen reduction reaction. The approaches are separated in two categories, namely ‘order-based’, which includes the use of alloying and preferential orientation and ‘disorder-based’, which includes the use of structural defects.

This presentation aims to provide insights into those different ways of enhancing the activity of Pt-based electrocatalysts, and in the limitations faced by this new generation of electrocatalysts. A special emphasis also is to be given to the mechanisms behind the formation, catalytic improvement and stability in operation of the platinum-nickel hollow nanostructures, one of those advanced electrocatalysts. These observations were made by studying the electrocatalyst synthesis and operation in-situ, taking advantage of several characterization methods such as scanning transmission electron microscopy, X-ray photoelectron spectroscopy, and small and wide-angle X-ray scattering, along with achieving a careful understanding of the platinum nanostructures' interactions with their carbonaceous support.

Bio: Tristan Asset obtained his Ph.D. in chemical engineering and material sciences in September 2017, on the synthesis and characterization of PtNi electrocatalysts for fuel cell applications, under the supervision of Dr. Laëtitia Dubau, Prof. Nathalie Job and Dr. Frédéric Maillard, from the University of Grenoble (France) and the University of Liège (Belgium). In 2018, he became a postdoctoral scholar at the University of New Mexico, in Professor Plamen Atanassov's group. His research focuses on (i) CO2 and N2 electrochemical reduction reaction and (ii) mechanistic, activity and durability studies on Pt-based and Pt-group-metal free for the oxygen reduction reaction (ORR), along with (iii) Al-air systems and (iv) metal oxides as supports for ORR electrocatalysts, topics that were added to his portfolio during his move to UC Irvine in January 2019. He co-authored 33 scientific articles and has a h-index of 15.

Join CBE-298 Seminar at: https://uci.zoom.us/j/91011181803