Co9S8@N,S-codoped carbon core–shell structured nanowires: constructing a fluffy surface for high-density active sites

Abstract

Developing earth-abundant catalysts to reduce reliance on noble-metal based ones in sustainable electrochemical processes is nowadays of great interest. Particularly, the rational structural design of electrocatalysts with high-density and well-exposed active sites is critically important to reach high catalytic activity. In this work, we have grown Co₉S₈ nanowires on carbon fiber paper via a hydrothermal route, and notably the Co₉S₈ nanowires are encapsulated in an unusual fluffy shell layer constructed using a continuous N,S-codoped carbon coating decorated with copious, vertically grown, short N,S-codoped carbon nanotube material. Such a nanowire/nanofluff combined structure provides not only many voids for rapid mass transfer, but also numerous specific surfaces for the loading of active sites, and it can be used well as a bifunctional catalyst in both oxygen evolution and hydrogen evolution reactions. Particularly, the obtained catalysts exhibit good oxygen evolution activity, showing a small overpotential of 290 mV to obtain a geometric current density of 10 mA cm⁻² in 1.0 M KOH electrolyte. Besides, the closely coated carbon layers also successfully prevent the Co₉S₈ nanowires from dissolution and recrystallization, thus leading favorably to good durability. Indeed, the reported fluffy carbon shell offers a novel structure design, with distinct advantages regarding the exposure of and access to high-density active sites, which can be extended to a variety of functional nanomaterials.