Electroreduction of oxygen on Vulcan carbon supported Pd nanoparticles and Pd-M nanoalloys in acid and alkaline solutions

Highlights: → Electroreduction of O2 on carbon-supported Pd, PdCo and PdFe nanoparticles is studied. → Pd-based catalysts were prepared by reduction in the presence of citrate and in microemulsion. → Four-electron reduction of O2 proceeds in both acid and alkaline media. → Specific activity of PdCo and PdFe nanocatalysts was similar to that of Pd nanoparticles. - Abstract: The kinetics of O2 reduction on novel electrocatalyst materials deposited on carbon substrates were studied using the rotating disk electrode (RDE) technique. Palladium nanoparticles and Pd-M (PdCo and PdFe) nanoalloys supported on Vulcan XC-72R were prepared using two different synthetic routes. The catalyst samples were examined by transmission electron microscopy (TEM) and the average size of metal nanoparticles was determined. Electrochemical measurements were performed in 0.5 M H2SO4 and in 0.1 M NaOH solutions. The influence of different synthetic conditions on the values of specific activity and other kinetic parameters was investigated. These parameters were determined from the Tafel plots taking into account the real electroactive area for each electrode. Pd nanoparticles and Pd-M nanoalloys exhibit significantly high electrocatalytic activity for the four-electron reduction of oxygen to water.