Enhanced catalytic activity for hydrogen electrooxidation and CO tolerance of carbon-supported non-stoichiometric palladium carbides

The promoting effect of incorporation of carbon atoms into the crystalline lattice of palladium on its electrocatalytic performance for the hydrogen oxidation reaction (HOR) and CO tolerance was found, for the first time, with the PdCx/C catalysts prepared via (1) treatment of the pre-deposited Pd particles with C2H4 at 300 °C and (2) successive calcination/reduction of a Pd/C precursor in flowing Ar and H2 at 250 °C. The formation of the interstitial PdCx solutions was confirmed by means of X-ray diffraction, high resolution transition electron microscopy and a set of electrochemical methods. The HOR on the as-prepared and CO-poisoned PdCx/C catalysts was studied using rotating disk electrode. For the catalysts prepared without the use of specially added carbon source (route 2), the correlation between the microstructure of a carbon support and the catalyst activity for the HOR is observed: the structurally more disordered supports give rise to the more active catalysts. The most active PdCx/C catalysts demonstrate up to a 2.5-fold increase in the exchange current density of the HOR and a rise of about 20-fold in the hydrogen oxidation current density in the presence of 1100 ppm CO comparing to the Pd/C catalysts.

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► Carbon-supported nanoparticles of Pd carbides as catalysts for H2 electrooxidation.
► Synthesis of PdCx/C catalysts via thermal treatment of Pd/C in flowing C2H4 or H2.
► Microstructure of carbon support determines plausibility of formation of Pd carbides.
► Interstitial carbon enhances catalytic activity of Pd in H2 electrooxidation.
► Interstitial carbon enhances CO-tolerance of Pd during H2 electrooxidation.