Effects of Pd Nanoparticle Size and Solution Reducer Strength on Pd/C Electrocatalyst Stability in Alkaline Electrolyte

The degradation of two commercial (E-TEK) electrocatalysts, made of palladium nanoparticles supported on Vulcan XC-72 (Pd/C) and differing by their average Pd nanoparticles diameter, was studied in alkaline and acidic solutions. The fate of the electrocatalysts upon accelerated stress test (AST) in 0.1 M NaOH was compared to that in 0.1 M H 2 SO 4 . Whereas Pd/C nanoparticles suffer dramatic degradation in 0.1 M H 2 SO 4 , electrochemical measurements combined with Identical-Location Transmission Electron Microscopy (ILTEM) demonstrate their higher stability in 0.1 M NaOH at 25°C than reported in the literature for Pt/C electrocatalysts (supported on the same support). As palladium is an efficient anodic material for direct alkaline fuel cells, the stability of Pd/C was investigated in the presence of reducing species in the alkaline electrolyte: alkaline electrolytes containing hydrogen or hydrazine borane yield slightly larger instability for the Pd/C nanoparticles, and the effect is less pronounced for large Pd/C nanoparticles than for small ones.