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.