Development of functionalized carbon nanofibers with integrated palladium nanoparticles for catalytic hydrogen generation

Abstract

The noble metals have the intrinsic ability to catalyze variety of useful reactions, however, their applications are hindered due to their high cost. One of the potential solutions is to reduce size of metal particles to enhance the number of surface metal atoms and thereby the catalytic activity. Herein, we synthesize palladium based heterogeneous catalysts using carbon nanofibers (CNFs) as support for the dehydrogenation of formic acid to hydrogen gas. The nitrogen species have been widely reported to enhance the metal-support interaction, therefore, CNFs were further functionalized with amine groups. We utilized strong electrostatic adsorption (SEA) method where charged metal precursors were strongly adsorbed onto oppositely charged carbon surface by controlling the pH relative to the point of zero charge (PZC). The effect of palladium loading on amine-functionalized carbon nanofibers (NH2-CNFs) over the range of pH from 2 to 12 as well as the effect of ionic strength of the solution on metal loading were thoroughly studied. These optimizations resulted in the best activity for dehydrogenation of formic acid using 4 nm Pd nanoparticles integrated over functionalized CNFs. Overall, the results indicate that Pd@NH2-CNFs were reusable, recyclable and active for the dehydrogenation of formic acid at ambient conditions.