Temperature and potential-dependent structural changes in a Pt cathode electrocatalyst viewed by in situ XAFS

Effect of heat treatment on the activity and stability of carbon supported PtMo alloy electrocatalysts for hydrogen oxidation in proton exchange membrane fuel cells

“…A greater increase in the magnitude of white line with the increase in the applied potential is observed for the catalyst of small particle size (1 nm) in comparison to large particle sized (3.7 nm) catalyst. This increase in white line intensity with increasing applied potential for the catalysts with two different particle sizes is associated with a modification of average Pt oxidation state and has been discussed in detail by various authors [31,36,37]. Mukerjee et al [9] observed a small increase in the Pt white line magnitude for PtMo/C when compared with Pt/C, indicating an increase in the number of Pt 5d band vacancies in PtMo/C due to alloying.…”

In Situ/Operando Electrocatalyst Characterization by X-ray Absorption Spectroscopy

“… 175 This fitting approach was used, for instance, by Witkowska et al in studies of Pt NPs for fuel cell cathodes. 176 A more general approach relies on the expansion of g p ( R ) in the so-called MacLaurin, or cumulant series: 152 …”

Evolution of the nanostructure of Pt and Pt–Co polymer electrolyte membrane fuel cell electrocatalysts at successive degradation stages probed by X-ray photoemission

“…Effect was strong enough to be also visible in XAS spectra [21]. For XPS measurements, this change may be reasonably attributed to the modifications in metallic granular structure (increase of particle size distribution asymmetry on the large-sized particle side) and to complete activation of Pt/C catalyst by 4-h conditioning at 70 C and 0.6 V. This means, that during this relatively short period a major component of soluble oxidized Pt species diffusing in the ionomer phase, probably mainly toward the membrane, precipitated on the other particles and/or migrated to the polymer membrane leaving the catalytic layer.…”