Pd nanoparticles supported on low-defect graphene sheets: for use as high-performance electrocatalysts for formic acid and methanol oxidation

Well-dispersed Pd nanoparticles supported on low-defect graphene (LDG) sheets are successfully prepared by a soft chemical method. Our approach can efficiently avoid damaging the graphene framework in the composite because it does not require cumbersome oxidation of graphite in advance and needs no subsequent reduction of the LDG sheets due to the lower oxidation degree. Morphology observations show that the Pd nanoparticles with diameters ranging from 1 to 5 nm are evenly deposited on graphene sheets. Raman spectroscopic analysis results reveals that there is only a very small amount of graphene defects in the hybrid. No matter whether it is for a direct formic acid fuel cell (DFAFC) or direct methanol fuel cell (DMFC), the LDG-supported Pd catalyst has very large electrochemically active surface area (ECSA) values, more than twice as large as that for the reduced graphene oxide, or five times the commercial XC-72 carbon. The forward peak current measurements show similar results. The excellent catalytic performance of LDG/Pd can be attributed to the preserved pristine graphene structure, which not only provides a lot of surface area for the deposition of nanoparticles, but also allows for electrical conductivity and stability in the composite.