In situ determination of the nanostructure effects on the activity, stability and selectivity of Pt-Sn ethanol oxidation catalysts

LAURA CALVILLO; LUCILA MÉNDEZ DE LEO; STEPHEN J. THOMPSON; STEPHEN W. T. PRICE; ERNESTO J. CALVO; ANDREA E. RUSSELL

JOURNAL OF ELECTROANALYTICAL CHEMISTRY

ELSEVIER

Lugar: Amsterdam; Año: 2018 vol. 819 p. 136 - 144

0022-0728

Nanoparticle catalysts comprising two PtSn alloys with different Pt:Sn atomic ratios and a Sn modified Pt catalyst were prepared in order to study the effect of the particle nanostructures on the activity towards the ethanol electrooxidation and the selectivity to CO2. An accurate model of the electronic and structural properties, obtained by ex situ analysis, was established. Alloying of Sn with Pt causes the expansion of the lattice parameter of Pt and modifies its electronic structure. In contrast, the deposition of Sn on the Pt surface has neither effect. The activity of the catalysts towards ethanol oxidation was established voltammetrically and the CO2 selectivity via in situ Fourier transform infrared spectroscopy (FTIRS). Results indicated that the modification of the electronic environment of Pt in Pt-Sn alloys results in a weaker adsorption of the intermediates (acetaldehyde and acetic acid), which desorb easily from the surface of the catalyst resulting in incomplete oxidation to CO2. In contrast, when the electronic structure is not perturbed (Sn modified Pt sample), the amount of CO2 produced increases. The stability of the different nanostructures under working conditions was investigated by in situ X-ray absorption spectroscopy (XAS) measurements, which show that initially both the Sn modified Pt and Pt-Sn alloy nanostructures are stable under applied potential in the potential window studied and in presence of ethanol. Accelerated aging studies showed that the Sn modified Pt nanostructure remained stable, whereas a significant structural change was observed for the Pt-Sn alloys.