Hierarchical assembly strategy to tailored nanostructures of doped-carbon/Co-based catalysts for high-performance trifunctional electrocatalysis

Abstract Developing an effective strategy to synthesize low-cost and efficient trifunctional electrocatalysts is critical to renewable energy storage and conversion but remains challenging. Herein, we report a hierarchical assembly strategy to controllably synthesize a series of doped carbon/Co-based nanocomposites with tunable morphologies and compositions. During the synthesis, a variation of urea/thiourea mass ratio exerts a dramatic effect on final nanostructures, ranging from hollow nanotube, nanosheet to nanospring. Meanwhile, Co species are successfully regulated from Co single atoms, Co nanoparticles (NPs) to Co9S8 NPs. The controllable tunability allows the optimization of trifunctional electrocatalytic performance and the establishment of structure/composition-property relationships for oxygen reduction reaction (ORR), oxygen evolution reaction (OER), and hydrogen evolution reaction (HER). Among the as-obtained materials, the heterostructure of hollow carbon nanotubes/reduced graphene oxide doped with N/S and decorated with Co9S8 NPs (Co9S8-HCT) shows superior electrocatalytic activity and long-term stability for ORR, OER, and HER in alkaline medium. Experimental and theoretical results show that the electrocatalytic promotion comes from the electronic modulation of Co9S8 from N,S-codoped nanocarbon.