Molecularly Engineered Carbon Platform To Anchor Edge-Hosted Single-Atomic M-N/C (M = Fe, Co, Ni, Cu) Electrocatalysts of Outstanding Durability

Abstract

A powerful synthetic protocol based on a molecularly engineered anchoring carbon platform (ACP) is reported to stabilize concentrated edge-hosted single-atom catalytic sites of M-N (M = Fe, Co, Ni, Cu) on carbon supports. Polymerization with L-cysteine as an additional organic precursor produces an ACP sheath around the carbon nanotube (CNT)-graphene (GR) hybrid support made of a small domain size with abundant edge sites and doped with sulfur. A few-minute-long microwave pyrolysis anchors strongly the single-atomic M-N moiety on the ACP while suppressing its agglomeration during the high-temperature synthesis and makes the ACP highly graphitized. As a typical example, the edge-hosted single-atomic catalytic sites in Fe-N/S-CNT-GR provide superior pH-independent oxygen reduction reaction (ORR) activity to previously reported Fe-N-C catalysts and commercial Pt/C while demonstrating oxygen evolution reaction (OER) activity in basic conditions similar to known state-of-the-art catalysts. In particular, the Fe-N/S-CNT-GR catalyst is much more stable than commercial Pt/C and Ir/C catalysts during ORR and OER in both base and acid solutions. Inferior stability is a common problem of this type of single-atom heterogeneous catalyst (SAC). An aqueous Zn-air battery with our Fe-N/S-CNT-GR catalyst operates as effectively as the device with the commercial Pt/C-Ir/C catalysts. We believe that our protocol based on the molecularly engineered ACP and microwave pyrolysis can provide a new concept to synthesize a new generation of durable SACs, which could have broad applications in electrochemical energy conversion and storage.