2,2′-bipyridine palladium (II) complexes derived N-doped carbon encapsulated palladium nanoparticles for formic acid oxidation

Doping nitrogen (N) into the carbon support was widely applied to enhance the performance of Pd toward formic acid electro-oxidation (FAO). However, traditional nitrogen doping methods can only introduce a low content of nitrogen as well as a two-step complicated procedure to synthesize catalysts. In this study, a facile one-pot strategy is demonstrated to prepare N-doped carbon encapsulated palladium nanoparticles ([email protected]xC) via the pyrolysis of 2,2′-bipyridine palladium (II) complexes. A N-doped carbon layer with the thickness of about 4 nm is in-situ generated over Pd nanoparticles by only one pyrolysis procedure. Both XPS and in-situ XRD results suggest that metallic Pd is reduced from Pd2+ by the complexed N in bipyridine during the pyrolysis at high temperature. The physical characterizations prove that the in-situ formation of N-doped carbon shell can not only effectively prevent the agglomeration or dissolution of Pd nanoparticles, but also promote the charge donation from the carbon layer to Pd, and maintain the structure of Pd atom complexed to two pyridinic-N atoms (Pd-N). This in-situ synthesis strategy can be successfully applied to carbon supports with different geometry, such as reduced graphene oxide and Vulcan XC-72. [email protected]3C/rGO, which contains the highest amount of N (7.39 at.%) and Pd-N (33.15%), shows the highest specific activity (5.88 mA cm−2) and excellent durability toward FAO.