Carbon nanotubes-supported colloidal Ag–Pd nanoparticles as electrocatalysts toward oxygen reduction reaction in alkaline electrolyte

Ag–Pd nanoparticles with compositional ratios of 1:1 (Ag1Pd1), 2:1 (Ag2Pd1), and 4:1 (Ag4Pd1) and supported on multiwall carbon nanotubes (CNTs) were prepared by the self-regulated reduction of sodium dodecyl sulfate, and then, they were used as catalysts for oxygen reduction reactions (ORRs) in 1 M NaOH solution. Polarization curves showed that, among the prepared nanocatalysts, Ag4Pd1/CNT nanocatalysts showed higher activity. During the ORRs, two types of oxygen coverages given by the Temkin isotherm and Langmuir isotherm were observed for low and high overpotentials, respectively. Koutecky–Levich plots showed that the number of electrons involved in the ORRs catalyzed by Ag1Pd1/CNT, Ag2Pd1/CNT, and Ag4Pd1/CNT were 2.11, 1.88, and 2.25, respectively. These ORRs proceeded through a two-electron pathway. Polarization curve in the electrolyte with methanol revealed that Ag4Pd1/CNT has high methanol tolerance during ORRs.