Use of Cobalt Polyphthalocyanine and Graphene as Precursors to Construct an Efficient Co9S8/N,S-G Electrocatalyst for the Oxygen Electrode Reaction in Harsh Media

The oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are fundamental reactions connected with energy conversion and/or storage devices. However, the sluggish kinetics of the ORR and OER reduce the efficiency. To address these issues, the development of efficient and robust electrode catalysts is required desperately. Herein, a new Co9S8 nanocrystal hybrid anchored on a N- and S-dual-doped graphene (Co9S8/N, S-G) was prepared by a two-step method, namely, a p-p assembly process of p-phenyl-bis(3,4-dicyanophenyl) thioether cobalt polyphthalocyanine (PTCoPPc) and graphene oxide and a pyrolysis procedure. Electrochemical studies demonstrated that Co9S8(800)/N,S-G exhibited a comparable ORR performance with 20 wt% Pt/C, such as an onset potential and a half-wave potential of 0.931 and 0.811 V vs. the reversible hydrogen electrode, respectively, a limiting current density of 5.207 mAcm(-2), and a good long-term stability with a current retention of 92.6% after 10 000 s continuous measurements. Co9S8(900)/N, S-G displayed an excellent OER activity, which was ascribed to the presence of pyridinic N, graphitic N, and the occupation of Co-N to catalyze the ORR; and the oxygen adsorption on the surface of Co9S8(900)/N, S-G contributed significantly to the OER activity. The approach developed here offered a new strategy to construct efficient oxygen electrode catalysts.