Facile Synthesis of Co₉S₈ Hollow Spheres as a High-Performance Electrocatalyst for the Oxygen Evolution Reaction

Cobalt pentlandite (Co₉S₈) has recently attracted great attention as a highly efficient and stable earth-abundant catalyst for the oxygen evolution reaction (OER) because of its electronic properties and intrinsic structure. However, the rational design and synthesis of OER catalysts to further enhance the electrochemical activity and durability remain major challenges. Herein, novel Co₉S₈ hollow spheres were successfully obtained through a template- and surfactant-free method, and they exhibit impressive electrocatalytic properties for the OER. Notably, the as-prepared material has superior OER performance with a low overpotential of 285 mV reached at 10 mA cm^-2, a Tafel slope of 58 mV decade^-1, and improved stability in 1 M aqueous solution KOH. Impressively, the unique hollow structure of Co₉S₈ hollow spheres imparts large surface area and abundant active sites, resulting in the superior catalytic activity. Thus, this work provides promising alternative cobalt sulfide-based oxygen evolution electrocatalysts to substitute for precious metal-based electrocatalysts.