One-step solid phase synthesis of a highly efficient and robust cobalt pentlandite electrocatalyst for the oxygen evolution reaction

Abstract

Cobalt pentlandite (Co₉S₈) has recently emerged as an alternative non-noble metal based electrocatalyst for the oxygen evolution reaction (OER). Co₉S₈ is known for its intrinsic structural and electronic properties favorable for electrocatalytic applications, but the synthesis of stoichiometrically optimal Co₉S₈ electrocatalysts remains challenging. Herein, a facile one-step solid phase calcination approach is presented in which Co₉S₈ nanoparticles (NPs) were concurrently synthesised on carbon nanosheets (CNSs). The reaction mechanism for this synthesis was systematically investigated using TG/DSC-MS analysis. Relative to other cobalt chalcogenide electrocatalysts, the as-prepared thermally stable nanocomposite (Co₉S₈/CNS) has better electrocatalytic performance for the OER in alkaline electrolytes, exhibiting a smaller overpotential of 294 mV at a current density of 10 mA cm⁻² with a Tafel slope of 50.7 mV dec⁻¹. Furthermore, a minimum overpotential of 267 mV with a Tafel slope of 48.2 mV dec⁻¹ could be achieved using highly conducting multi-walled carbon nanotubes (MWCNTs) as a conducting filler in the nanocomposites.