Determination of the electrochemically active surface area by CO and hydrogen of PtSnRuTa/C-based electrocatalysts and their relationship with catalytic activity against alcohol oxidation

This work studies the influence of the addition of tantalum to the ternary PtSnRu/C electrocatalysts on the oxidation of different alcohols: methanol, ethanol, ethylene glycol, and glycerol. The physical-chemical characterizations showed an increase in the lattice parameter of the fcc (face-centered cubic) structure of Pt due to the incorporation of Sn and/or Ta metals that evidence of alloy formation. The nanoparticles range from 3.8 to 9.8 nm and present a homogeneous distribution on carbon. CO stripping voltammetry measurements were used to obtain the electrochemically active surface area (ECSA) of electrocatalysts, which showed higher values for the quaternary electrocatalysts of composition Pt24.8Sn5.0Ru1.0Ta7.7/C (21.3 m(2) g(Pt)(-1)), Pt8.1Sn1.3Ru1.2Ta1.0/C (29.3 m(2) g(Pt)(-1)), and Pt8.9Sn1.0Ru1.5Ta1.5/C (39.4 m(2) g(Pt)(-1)). The Pt8.9Sn1.0Ru1.5Ta1.5/C electrocatalyst presented high peak currents, compared with the other electrocatalysts, using cyclic voltammetry for methanol, ethanol, ethylene glycol, and glycerol. In chronoamperometry on ethanol, ethylene glycol, and glycerol, the Pt8.9Sn1.0Ru1.5Ta1.5/C electrocatalyst showed higher currents (24, 18, and 19 A g(Pt)(-1), respectively) compared to the other electrocatalysts. The results showed that the addition of Ru and Ta on PtSn/C nanoparticles led to an increase in the ECSA values. It can be suggested that the presence of the quaternary electrocatalyst maximizes the electronic and bifunctional mechanism which are responsible to increase the electrocatalytic activity to the alcohol oxidation. In addition, the presence of Ru and Ta together with Sn on Pt/C nanoparticles was also related to increased stability, representing an alternative for use in direct alcohol fuel cells.