An analysis of X-ray absorption spectra in the XANES region of platinum-based electrocatalysts for low-temperature fuel cells

The knowledge of the electronic state of Pt-based electrocatalysts used in low temperature fuel cells is very important for the understanding of the activity of the material. Near-edge X-ray absorption spectroscopy (XANES), a particular region of the X-ray absorption spectra (XAS), can provide the desired information, but the analysis is not straightforward, particularly for the non-specialist. Mansour et al. (J. Phys. Chem., 88:2330, 1984) and Shukla et al. (J. Electroanal. Chem., 563:181, 2004) presented methods to obtain information on electronic states from XANES spectra. In this work, procedures to implement the two methods are presented in detail and applied to XANES results for Pt₂Sn₁/C and Pt/C electrocatalysts prepared in this laboratory. The scope and limitations of the two methods are also discussed. The results show that the presence of Sn in the Pt₂Sn₁/C material promotes a partial filling of the Pt 5d band, in comparison to Pt/C, which contributes to explain the better activity of the bimetallic material. This paper is dedicated to Prof. Francisco Nart, in memoriam.