Direct pyrolysis and ultrasound assisted preparation of N, S co-doped graphene/FeC nanocomposite as an efficient electrocatalyst for oxygen reduction and oxygen evolution reactions.

Bifunctional electrocatalysts to enable efficient oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are essential for fabricating high performance metal-air batteries and fuel cells. Here, a defect rich nitrogen and sulfur co-doped graphene/iron carbide (NS-GR/FeC) nanocomposite as an electrocatalyst for ORR and OER is demonstrated. An ink of NS-GR/FeC is developed by homogeneously dispersing the catalyst in a Nafion containing solvent mixture using an ultrasonication bath (Model-DC150H; power - 150 W; frequency - 40 kHz). The ultrasonically prepared ink is used for preparing the electrode for electrochemical studies. In the case of ORR, the positive half-wave potential displayed by NS-GR/FeC is 0.859 V (vs. RHE) and for the OER, onset potential is 1.489 V (vs. RHE) with enhanced current density. The optimized NS-GR/FeC electrode exhibited excellent ORR/OER bifunctional activities, high methanol tolerance and excellent long-term cycling stability in an alkaline medium. The observed onset potential for NS-GR/FeC electrocatalyst is comparable with the commercial noble metal catalyst, thereby revealing one of the best low-cost alternative air-cathode catalysts for the energy conversion and storage application.