Authors: Yashraj Gartia, Charlette M. Felton, Fumiya Watanabe, Peter Szwedo, Alexandru S. Biris, Nandan Kumar Peddi, Zeid A. Nima, and Anindya Ghosh
Publication: ACS Sustainable Chemistry and Engineering, Issue 3, Volume 1
A nanocomposite of a dichloro-amido-macrocyclic cobalt(III) complex (1) and graphene was developed and characterized using various microscopic and spectroscopic techniques such as X-ray photoelectron spectroscopy, transmission electron microscopy, scanning electron microscopy and Raman spectroscopy. The nanocomposite was evaluated for electrocatalytic activity toward oxygen reduction reaction (ORR) in fuel cell applications. This complex (1) showed efficiency in a wide range of pH (acidic and basic) conditions for successful ORR. Apart from pH studies, the ratio of electrocatalyst 1 to graphene was varied for developing the optimal ORR catalyst. The use of graphene as a carbon support along with 1 in ORR studies not only resulted in increased current density but also a positive shift of the reduction potential by 140 mV (with respect to the Ag/AgCl reference electrode). Investigation of the catalytic mechanism using rotating disk electrode and rotating ring-disk electrode studies revealed its mechanism in acidic and basic conditions. The ORR was found to be a four-electron process in both pH conditions. The rate constant of ORR activity was found to be 3.85 × 105 mol–1s–1 at pH 2.0. The efficiency of the nanocomposite in ORR indicates the advantage of using both 1 and graphene for fuel cell applications.