Synthesis of PtAg bimetallic material as a multi-fuel tolerant electrocatalyst and spectroelectrochemical analysis of its capability to perform the oxygen reduction
By Vargas-Ordaz, M.; Velázquez-Hernández, I.; Bañuelos, Jennifer A.; Ledesma-García, J.; Álvarez-Contreras, L.; Arjona, N.; Guerra-Balcázar, M.
Published in Materials Today Energy
2019
Abstract
Fuel crossover is one of the issues that limit the cell performance of direct alcohol fuel cells. In this work, Pt and PtAg were easily prepared by electrodeposition on glassy carbon electrodes, and tested as tolerant electrocatalysts to alcohol fuels. The physicochemical characterization indicated that crystallite sizes of 4.1 and 3.0 nm were found for Pt and PtAg, respectively. In addition, according with high-resolution scanning electron microscopy, Pt displayed a rosette-like morphology of few tens of nanometers in size, while PtAg was composed mainly by cubes. These arrangements were composed by smaller nanoparticles of 4.3 ± 0.3 nm to Pt, and 3.2 ± 0.2 nm to PtAg as was determined by high-resolution transmission electron microscopy. PtAg had a 3:1 Pt:Ag composition resulting in a Pt75Ag25 catalyst. Moreover, 66.42% of the silver content in the Pt75Ag25 catalyst was in an alloyed form. The electrocatalytic evaluation toward the oxygen reduction reaction (ORR) indicated that PtAg required more energy (90 mV) than Pt to perform this reaction. Tolerance tests were performed introducing 0.1 M of methanol, ethanol, ethylene glycol and glycerol throughout the ORR, finding that these fuels were preferably oxidized in presence of Pt instead the ORR. PtAg displayed an opposite behavior acting as a multi-fuel tolerant material. A spectroelectrochemical analysis confirmed that Pt has affinity to promote the fuels dissociative adsorption instead the oxygen adsorption and thus, the electro-oxidation reactions. The multi-tolerant capability of PtAg was related to the absence of any band related to the dissociative adsorption of methanol, ethanol and ethylene glycol.