Stability of carbon-supported palladium nanoparticles in alkaline media: A case study of graphitized and more amorphous supports

Abstract

The stability and degradation mechanism of graphitized (Graphene nanosheets) and more amorphous (Vulcan XC-72R) carbon-supported palladium nanoparticles was investigated. Coupling identical-location transmission electron microscopy (ILTEM) and electrochemistry enabled to correlate the distribution of the Pd nanoparticles under accelerated stress test (up to 1000cycles between 0.1 and 1.23V vs. RHE, in a 0.1M NaOH solution at 25°C) with changes in electrochemical accessible surface area (ECSA). The carbon-supported Pd nanoparticles undergo similar rates of degradation in terms of electrochemical surface areas on both supports. However, their mechanisms of degradation differ: on amorphous carbon, the primary mode of degradation is Pd nanoparticles detachment (and minor agglomeration), whereas on graphitized supports it is more likely their coalescence and dissolution/redeposition. “Bulk” carbon-corrosion is negligible in both cases, as proven by ex situ Raman spectroscopy. So, using a graphitized carbon support (Graphene nanosheets) versus a more amorphous one (Vulcan XC-72R) does not enable to significantly depreciate the Pd/C catalyst degradation in alkaline media.