In situ synthesis of mesoporous manganese oxide/sulfur-doped graphitized carbon as a bifunctional catalyst for oxygen evolution/reduction reactions

Low cost materials with high electrochemical catalytic activity for oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) are in urgent demand for energy storage and conversion devices. In this work, we propose a novel and environmentally-friendly approach to synthesize in situ a meso-porous MnO_x/S doped graphitized carbon (MnO_x/S-GC) hybrid with a specific surface area of 502.6 m² g^-1. The synthesis involves the thermal treatment of polyvinyl chloride (PVC) together with KMnO₄ and (NH₄)₂Fe(SO₄)₂. It is the first time a MnO_x/S-GC hybrid is fabricated directly from a carbon source without any intermediate products such as graphene oxide or additional chemical reagents. In addition, since PVC is the major component of plastics, this method has provided a new approach for the utilization of waste. Most importantly, the as-prepared hybrid showed a high catalytic activity towards both ORR and OER. The current density reached -3 mA cm^-2 at 0.81 V and 10 mA cm^-2 at 1.62 V vs. reversible hydrogen electrode respectively.