PdAg/C Electrocatalysts Synthesized by Thermal Decomposition of Polymeric Precursors Improve Catalytic Activity for Ethanol Oxidation Reaction

An efficient ethanol oxidation reaction (EOR) is required to enhance energy production in alcohol-based fuel cells. The use of bimetallic catalysts promises decreasing reliance on platinum group metal (PGM) electrocatalysts by minimizing the use of these expensive materials in the overall electrocatalyst composition. In this article, an alternative method of bimetallic electrocatalyst synthesis based on the use of polymeric precursors is explored. PdAg/C electrocatalysts were synthesized by thermal decomposition of polymeric precursors and used as the anode electrocatalyst for EOR. Different compositions, including pristine Pd/C and Ag/C, as well as bimetallic Pd₈₀Ag₂₀/C, and Pd₆₀Ag₄₀/C electrocatalysts, were evaluated. Synthesized catalysts were characterized, and electrochemical activity evaluated. X-ray diffraction showed a notable change at diffraction peak values for Pd₈₀Ag₂₀/C and Pd₆₀Ag₄₀/C electrocatalysts, suggesting alloying (solid solution) and smaller crystallite sizes for Pd₆₀Ag₄₀/C. In a thermogravimetric analysis, the electrocatalyst Pd₆₀Ag₄₀/C presented changes in the profile of the curves compared to the other electrocatalysts. In the cyclic voltammetry results for EOR in alkaline medium, Pd₆₀Ag₄₀/C presented a more negative onset potential, a higher current density at the oxidation peak, and a larger electrically active area. Chronoamperometry tests indicated a lower poisoning rate for Pd₆₀Ag₄₀/C, a fact also observed in the CO-stripping voltammetry analysis due to its low onset potential. As the best performing electrocatalyst, Pd₆₀Ag₄₀/C has a lower mass of Pd (a noble and expensive metal) in its composition. It can be inferred that this bimetallic composition can contribute to decreasing the amount of Pd required while increasing the fuel cell performance and expected life. PdAg-type electrocatalysts can provide an economically feasible alternative to pure PGM-electrocatalysts for use as the anode in EOR in fuel cells.