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A series of (super 195)Pt and (super 13)C NMR spectroscopic and electrochemical experiments on commercial Pt-Ru alloy nanoparticles is carried out and the results are compared with those on Pt-black samples having similar particle sizes. An analysis of the (super 13)C spin-lattice relaxation results indicates that Ru addition causes a reduction in the Fermi level local density of states of the clean metal surface atoms and the 2pi orbital of adsorbed CO.

The first combined application of solid-state electrochemical NMR (EC NMR), cyclic voltammetry (CV) and potentiostatic current generation is reported. This is done in order to investigate the topic of ruthenium promotion of MeOH electro-oxidation over nanoscale platinum catalysts.

Electrochemical nuclear magnetic resonance (EC-NMR) and X-ray photoelectron spectroscopy (XPS) are used for examining the modification of the electronic properties of Ru due to the addition of selenium. The results have shown that Se, a p-type semiconductor in elemental form, has become metallic when interacting with Ru in Ru-Se catalysts, due to charge transfer from Ru to Se.

(super 195)Pt NMR spectroscopic and electrochemical measurements are carried out on commercial Pt-Ru alloy nanoparticle samples to investigate the effect of high temperature annealing in different vacuum/gas-phase environments. The results suggest that optimizing the amount of surface Ru by heat treatment at temperatures near 200 degree Celsius, in a hydrogen atmosphere, is utilized to produce Pt-Ru alloy nanoparticles with high methanol oxidation activity.

The first observation of the (super 13)C nuclear magnetic resonance spectroscopy (NMR) of (super 13)CO, adsorbed from the (super CO) saturated 0.5M sulfuric acid solutions, onto the surfaces of commercial Ru-black nanoparticles is reported. The results indicates that the CO adsorption bond is weaker on Ru as compared to either Pt or Pd and is supported by a reduction in the activation energy for CO diffusion on Ru versus either Pt or Pd nanoparticles.

The first direct determination of the diffusion constants of CO on Pt in a liquid electrochemical environment, together with the activation energy for diffusion using the techniques of electrochemical NMR and selective spin inversion NMR is reported. Results reveal a new route to the study of surface diffusion of adsorbed molecules on nanoparticle electrode catalysts at the solid/liquid interface.

Indirect nuclear spin–spin J-coupling measurements have been carried out on a conducting, carbon-supported 8.8 nm platinum electrocatalyst by using 195Pt NMR. The J-coupling values show a marked variation across the spectrum. These J-coupling values were then transformed into the corresponding s-like Fermi level local density of states Ds(Ef,x), where x is the distance from the particle surface, revealing a spatially resolved oscillatory decay in Ds(Ef) which is responsible for the line broadening of the bulk peak in the 195Pt NMR spectrum. [Copyright &y& Elsevier]

Investigates the carbon monoxide tolerance in a Pt/Ru fuel cell catalyst. Performance of the nuclear magnetic resonance; Correlation between the Fermi level local density of states and the steady-state current; Comparison between fuel cells and conventional power generation sources.

(195)Pt NMR spectroscopic and electrochemical measurements were carried out on commercial Pt-Ru alloy nanoparticle samples to investigate the effect of high-temperature annealing in different vacuum/gas-phase environments. Samples annealed at 220 degrees C in Ar gas, or in a vacuum, did not show any demonstrable change in catalytic activity vs electrochemically reduced, room-temperature samples. In contrast, annealing at 220 degrees C in H(2) gas led to a 3-fold increase in reactivity toward methanol oxidation (per surface site). NMR experiments show that annealing at 220 degrees C (in both Ar and H(2)) leads to a slight reduction in the Fermi level local density of states (E(F)-LDOS) at the Pt sites, which we attribute to surface enrichment of Ru. This electronic effect alone, however, appears to be too small to account for the increase in the catalytic activity observed for the H-treated catalyst. By comparing the electrochemical and NMR data of the H- and Ar-treated samples, we conclude that annealing at 220 degrees C in the hydrogen atmosphere reduces surface Ru oxides into metallic Ru, and consequently, the presence of metallic Ru and its enrichment on the surface are essential for the enhanced catalytic activity. In contrast, heat treatment at 600 degrees C in both vacuum and argon atmosphere increases the particle size and reduces the amount of platinum on the nanoparticle surface, thereby increasing the surface Ru content beyond the optimum surface composition values. This causes a large reduction in catalytic activity. Our results suggest that optimizing the amount of surface Ru by heat treatment at temperatures near 200 degrees C, in a hydrogen atmosphere, can be utilized to produce Pt-Ru alloy nanoparticles with high methanol oxidation activity. Finally, our NMR and electrochemical data, taken together with the lattice parameter measurements, lead to a novel model of Pt-Ru alloy nanoparticles having a Ru-rich core and a Pt-Ru alloy overlayer.

We report the first combined application of solid-state electrochemical NMR (EC NMR), cyclic voltammetry (CV), and potentiostatic current generation to investigate the topic of the ruthenium promotion of MeOH electro-oxidation over nanoscale platinum catalysts. The CV and EC NMR results give evidence for two types of CO: CO on essentially pure Pt and CO on Pt/Ru islands. There is no NMR evidence for rapid exchange between the two CO populations. CO molecules on the primarily Pt domains behave much like CO on pure Pt, with there being little effect of Ru on the Knight shift or on Korringa relaxation. In sharp contrast, COs on Pt/Ru have highly shifted (13)C NMR resonances, much weaker Korringa relaxation, and, at higher temperatures, they undergo thermally activated surface diffusion. For CO on Pt, the correlation observed between the 2pi* Fermi level local density of states and the steady-state current suggests a role for Ru in weakening the Pt-CO bond, thereby increasing the CO oxidation rate (current). The combined EC NMR/electrochemistry approach thus provides new insights into the promotion of CO tolerance in Pt/Ru fuel cell catalysts, in addition to providing a novel route to investigating promotion in heterogeneous catalysis in general.