▎ 摘　　要

We report the synthesis of a nano-spinel cobalt decorated sulphur doped reduced graphene oxide (Co@S-rGO) composite exhibiting excellent electrocatalytic performance and electrochemical stability toward oxygen evolution reaction (OER) in an alkaline medium. Moreover, the so crafted noble metal free Co@S-rGO electrocatalyst, well characterized by UV-Vis spectroscopy, FTIR, XRD, SEM, and energy dispersive X-ray spectroscopy, exhibits promising activity toward electrochemical sensing of H2O2. For OER in an alkaline medium, the Co@S-rGO composite exhibits a Tafel slope of ca. 49 mV dec(-1), with an overpotential requirement of just 389 mV for a specific current density of 10 mA cm(-2). In the OER electrochemical stability tests, the Co@S-rGO electrocatalyst could maintain its peak OER performance for a time span of about 50 000 seconds during chronoamperometric measurements, while in the linear sweep voltammetry records almost negligible difference was observed between the final and the initial scan in a total of 1000 scans recorded over 25 hours for OER over Co@S-rGO. These chronoamperometric and voltammetric observations establish the excellent activity and long-term electrochemical stability of Co@S-rGO for OER in alkaline media. These current/potential and stability parameters observed for the OER performance of the Co@S-rGO composite are far better than that reported for various non-noble metal based state-of-the-art materials specifically crafted for OER. For the electrochemical sensing of H2O2, the Co@S-rGO composite exhibits a limit of detection as low as 23 nM with a sensitivity of 22743.85 mu A M-1 cm(-2). The excellent OER performance and H2O2 sensing activity of the Co@S-rGO composite can be attributed to the special synergism between the Co and S-rGO components and the extended electrochemically active surface area of Co nanodeposits in this noble metal free electrocatalyst.