Reduced-Graphene-Oxide with Transition Metal Hexacyanometallates As Active Support for Traces of Platinum Catalyst at Low Loading during Oxygen Electroreduction

Abstract

Reduced graphene-oxide-supported the various metals analogue of polynuclear Prussian Blue are considered here together with traces of platinum as well as low loadings of platinum (10-15 mg cm-2) as catalytic materials for reduction of oxygen in acid media. Comparison is made to the analogous systems based on conventional Vulcan carbon carriers. Electrocatalysts based on graphene and graphene-oxide (GO) are more homogeneous and possess properties such as excellent conductivity, good chemical stability and can be functionalized in a controlled manner. Following the heat-treatment step at higher temperatures, some thermal decomposition of the cyanometallate network occurs and, consequently, metallic sites are generated. The resulting material has occurred to show highly potent electrocatalytic properties toward electroreductions of oxygen in acid solution (the highest currents and the most positive electroreduction potentials) using cyclic and rotating ring-disk electrode (RDE) voltammetric experiments. Among important issues are possible activating interactions between analogue of Prussian Blue, platinum nanoparticles and the support, as well as presence of structural defects existing on poorly organized graphitic structure of reduced graphene oxide (as evident from Raman spectroscopy). An electrocatalytic system, that utilizes metal hexacyanometallates nanoparticles with trace amount of Pt modified reduced graphene-oxide-supported is also characterized here by additional diagnostic experiments, namely galvanodynamic measurements with use of so called gas diffusion electrode (GDE) operating under conditions resembling those characteristic of the cathode in a real fuel cell.