Evidence of surface restructuration on Pt–Rh/C and Pt–Rh–Ni/C nanoparticles applied to ethanol electrooxidation reaction

Abstract

In this work, it is provided evidence of surface catalyst reconstruction on Pt–Rh/C and Pt–Rh–Ni/C alloys during the course of the ethanol oxidation reaction. Pt–Rh/C and Pt–Rh–Ni/C nanoparticles were synthesized by a chemical reduction method using sodium borohydride as a reducing agent. The characterization by X-ray diffraction analysis revealed distortions in the Pt lattice parameters for the Pt–Rh and Pt–Rh–Ni catalysts, due to the different atomic radii of the Rh and Ni substituents of the Pt atom in the structure of the alloys. Transmission electron microscopy analyses indicate that nanoparticles were distributed in island shapes, in clusters of various nanoparticles, with spherical shapes and particle sizes of 2–6 nm. It was observed an improvement in the electrocatalytic activity and stability on all materials studied due to the reconstruction of their surfaces during many cycling in the presence of ethanol. Additionally, in situ FTIR experiments evaluated before and after 100 voltammetric cycles in presence of ethanol suggest that the surface reconstruction affects the reaction by modifying the yield of the products, thus increasing the production of CO2 in detriment of acetic acid formation.