Improved carbon dioxide selectivity during ethanol electrooxidation in acid media by Pb@Pt/C and Pb@PtSn/C electrocatalysts

Abstract

One key challenge for the fuel cell technology commercialization is the development of low Pt charge electrocatalysts with high fuel oxidation efficiency. Here, we evaluate the electrocatalytic performance of Pb1@Pt3/C and Pb1@Pt3Sn1/C core–shell and Pt3Sn1/C alloy nanocatalysts towards ethanol oxidation, evidencing the contributions provided when a PtSn alloy is present in the shell of these materials. Physical characterizations confirm the presence of Pb, Pt, and/or Sn in the catalytic composites, and the interaction between them from displacements in lattice parameters of core–shell materials. TEM results indicated the presence of small particles supported on carbon with some agglomeration. The 4f region profiles of Pt and Pb obtained from the XPS measurements suggest the formation of core-shell structure for the Pb1@Pt3/C and Pb1@Pt3Sn1/C electrocatalysts, which is in good agreement with their voltammetric profile, considering the inhibition of the hydrogen adsorption process caused by the presence of Sn on the surface of Pb1@Pt3Sn1/C. The core–shell electrocatalysts display the best electrocatalytic activities. The bimetallic Pb1@Pt3/C catalyst achieves the lowest onset oxidation potentials and the highest current density thus shows the positive changes provided by core–shell morphology from its electronic and geometric effects. Besides, in situ Fourier transform infrared spectroscopy measurements show that Pb1@Pt3/C and mainly Pb1@Pt3Sn1/C yields the highest CO2 production. Therefore, the presence of Sn makes the Pb1@Pt3Sn1/C electrocatalyst much more selective to CC bond breaking and CO2 production than the Pb1@Pt3/C. These outcomes can result from the combination of the electronic and geometric effects (core–shell) and the presence of Sn in the shell that promotes the bifunctional mechanism.