Electrochemical Synthesis of Palladium Single Atom Catalysts on Sulfur Doped Graphene

Highly dispersed nanoparticles have been shown to provide a more cost-effective catalyst through increased exposure to active sites. Electrodeposition provides a promising synthesis technique to deposit copper nanoparticles on a sulfur doped graphene support. Overpotential deposition (OPD), is commonly used for plating metals, however, the nucleation and growth of particles using OPD results in an inhomogeneous distribution of sizes and allows particles to aggregate and become larger, thus decreasing the active sites per total quantity of deposited metal. Underpotential deposition (UPD) on sulfur doped graphene provides a potential alternative. Sulfur, a common catalyst poison provides increased attraction between the deposited metal and the graphene support but does not poison the catalyst as the sulfur is contained in the graphene structure. Therefore, during UPD, copper is only deposited onto the sulfur sites. Initial testing of this concept has shown it to be successful at bench scale. Further testing is being done to optimize and the process and characterize the effects of changing the duration of deposition, concentration of the copper solution and other variables. Scanning transmission electron microscopy (STEM) with energy-dispersive X-Ray spectroscopy (EDX) will be used to characterize each catalyst. Once a highly dispersed copper on sulfur doped graphene catalyst has been synthesized and shown through the characterization techniques above to have nanoclusters, the copper will be galvanically displaced in a palladium solution to create a highly dispersed palladium on carbon catalyst.