Dr. Ivan Khalakhan and co-workers have studied the impact of the operating conditions of a proton-exchange-membrane fuel cell (PEMFC) on a Pt-Ni cathode catalyst. The aim was to gain fundamental insights into the changes in its surface composition.
A PtNi alloy catalyst was exposed alternately to oxidizing (O2) and reducing (H2) atmospheres, which simulated the cathode working conditions inside a real fuel cell. The oxidizing environment caused the formation of nickel oxides and an increase in the surface concentration of nickel. These chemical changes were largely but not fully reverted in the reducing environment. After five consecutive cycles, the surface remained not only nickel-enriched but also appreciably coarsened. All the changes were more pronounced at higher temperatures.
The findings have deepened our understanding of the structural dynamics of bimetallic catalysts during interaction with reactive environments. Such understanding is a prerequisite for the development of efficient PEMFC cathode catalysts.
The results are presented in the article entitled "Irreversible structural dynamics on the surface of bimetallic PtNi alloy catalyst under alternating oxidizing and reducing environments", which has been published in a high-impact journal, Applied Catalysis B: Environmental.