In Situ Synchrotron X-ray Spectroscopy of Ruthenium Nanoparticles Modified with Selenium for an Oxygen Reduction Reaction

Abstract

We used in situ Se K-edge X-ray spectroscopy to characterize Ru nanoparticles chemically modified with submonolayers of selenium (Se/Ru) [Cao et al. J. Electrochem. Soc. 2006, 153, A869]. X-ray powder diffraction verified that the Se/Ru catalyst had metallic Ru cores. The in situ X-ray absorption near edge structure taken at the open circuit potential showed that there were both elemental and oxidized selenium on the as-prepared Se/Ru samples. All selenium oxide was reduced to the elemental form of selenium by applying negative potentials. By applying positive potentials, selenium was subsequently reoxidized. The analysis of the extended X-ray absorption fine structure shows the appearance of selenium hydration (Se-OH 2 ) in a deaerated solution, which was not observed during the oxygen reduction reaction. We present evidence that Se-free Ru atoms play an important role in the ORR activity of the Se/Ru catalyst studied in this paper.

Aqueous-based synthesis of ruthenium–selenium catalyst for oxygen reduction reaction

“…A similar phenomenon, i.e. a non-plateau current region, was also observed in other Se/Ru(Se)-based catalysts 12,13,[30][31][32][33][34][35][36] and, more generally, with Ru-based catalysts. 6,7,37 Under such conditions, it is difficult to determine the value of the diffusion-limited currents.…”

“…10,23 For the catalysts prepared by modifying Ru by Se, the optimal Se content for the sample has been somewhat lower-about 30 at%. 17,32,33 In this latter case, the Se atoms are present on the catalyst surface only. As shown above, the optimized Se/Ru(Se)/C catalyst based on the RDE data had 20 wt% metal loading on carbon with the Ru : Se composition of 64 : 36 at%.…”

Incorporation of Pd into Au(111): enhanced electrocatalytic activity for the hydrogen evolution reaction

“…For this reason, it has to be clarified if the mechanism of Pd incorporation is related with a kind of spontaneous deposition, which is known for other systems. [49][50][51] On a thermodynamic basis, incorporation of Pd into bulk Au is favored, since the enthalpy of mixing is always negative and the surface free energy of Pd is higher than that of Au. 52,53 Recent calculations demonstrate the increased stability of Pd at sub-surface sites of Au(111) surfaces.…”

New Concepts in the Chemistry and Engineering of Low‐Temperature Fuel Cells

“…Two representative in situ synchrotron methods are X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) [187,198,200,201,[208][209][210][211][212], in which scattered photoelectrons are collected and analyzed to determine the energetic structure of catalytic nanoparticles (for EXAFS, see the blue trace in Fig. 19.7).…”