Boosting Oxygen Evolution Reaction on Metallocene-based Transition Metal Sulfides Integrated with N-doped Carbon Nanostructures.

In this study, utilizing metallocene and organosulfur chelating agent, we report an innovative synthetic route to electrochemically activated transition metal sulfides entrapped in pyridinic nitrogen-incorporated carbon nanostructures for superior oxygen evolution reaction (OER). Most importantly, preferential electrochemical activation process, which consists of both anodic and cathodic pre-treatment steps, strikingly enhance OER and long-lasting cyclic stability. The substantial increase in OER electrocatalytic activity of Ni9S8/Ni3S2-NC and Co9S8-NC during the activation process is mainly attributed to the increase of faradaic active site density on the catalytic layer resulting from the reconstruction of catalytic interfaces. We also found that Fe-based metallocene (ferrocene (Fc))-incorporation in the Co9S8-NC and Ni9S8/Ni3S2-NC nanostructures have significantly boost the OER activity. Thus, the combined effects of Fc-incorporation and the electrochemical activation process reduced the overpotential of about ~115 mV and ~95 mV on the Ni9S8/Ni3S2-NC and Co9S8-NC nanostructures to derive a current density of 10 mA cm-2, respectively. Notably, Fc-Ni9S8/Ni3S2-NC electrocatalysts needing a very small overpotentials of ~222 mV, ~244 mV, and ~280 mV to acquire the current densities of 10, 20, and 50 mA cm-2, respectively. This work opens up a new avenue for superior OER electrocatalysts by the utilization of metallocene and the preferential electrochemical activation process.