The rate of electron transfer between electrode surfaces and redox-active species is determined by such factors as the density of states (DOS) of the electrode material and specific adsorption/coordination of the redox moiety at the heterogeneous interface. Platinum is state-of-the-art for fast electron transfer while carbon electrodes, which have semi-metal electronic character, typically exhibit sluggish electron-transfer kinetics. Ruthenium dioxide is one of the few oxides to exhibit metal-like conductivity, DOS, and excellent kinetics for technologically relevant electrochemical reactions, yet its applications are often limited by cost. Herein we use low-temperature, solution-based electroless deposition protocols to apply conformal nanoscopic ruthenia (RuO2) to ~100 nm–thick carbon films formed by chemical-vapor deposition methods. The resulting electrode surfaces were evaluated via cyclic voltammetry in aqueous electrolytes that contained either inner-sphere (e.g., ferricyanide and iron-aquo complexes) or outer-sphere redox probes; the respective electron-transfer rates were determined by established electroanalytical methods. Even at low loadings and nanoscale thickness, the RuO2 coatings significantly enhance electron-transfer kinetics, particularly after heat treatment to crystallize the disordered RuO2 domains to their rutile form. The electrochemical properties of RuO2@carbon electrodes are benchmarked against native carbon and platinum counterparts.

Studying the kinetics of electrochemical reactions on ruthenia-coated carbon electrodes

253rd National Meeting (2017)

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