Thermally-Activated Cobalt Hexacyanocobaltate Dispersed on Reduced-Graphene-Oxide As Electrocatalyst Towards Oxygen Reduction in an Alkaline Medium

Abstract

In the recent research years is observed huge interest in design of new functional nanomaterials for developing new electrocatalysts for oxygen reduction reaction (ORR) in acid and alkaline media. The research has been focused on developing carbon nanostructures materials with the different transition metals (e.g. Co, Ni, Ag, Au, Cu, Mn) analogue of polynuclear Prussian Blue for fuel cell applications. The development of electrocatalytic material prepared by heat-treating a composite of a Prussian Blue analogue - cobalt hexacyanocobaltate immobilized on a reduced graphene oxide. The pyrolysis process, forms a new type of catalyst with efficient active cobalt centers (Co-N-C and Co-C-N) of electrochemical oxygen reduction reaction in alkaline media. Physicochemical properties of this catalytic material containing cobalt in differing oxidation states were elucidated using microscopic, spectroscopic methods and various electrochemical diagnostic techniques. Experimental results showed that the cobalt analogue of Prussian Blue displayed comparable electrocatalytic activity (e.g., a half-wave potential and overpotential) towards oxygen reduction reaction in alkaline media to Vulcan-supported platinum nanoparticles. Furthermore, the presence of cyanide-bridged cobalt ionic sites tended to decrease formation of undesirable peroxide intermediate species, as demonstrated by monitoring ring currents during RRDE measurements. Furthermore, the proposed electrocatalytic material exhibits great stability and tolerance to alcohols (e.g. methanol). Acknowledgement The study was supported by the National Science Center (NCN), Poland, Project Number 2015/19/B/ST4/03758