Metathesis Reaction to Form Nanosheet-Structured Co(OH)₂ Deposited on N-Doped Carbon as Composite Electrocatalysts for Oxygen Reduction

Developing effective non-precious metal electrocatalysts for oxygen reduction reaction (ORR) with a simple synthesis procedure is of great importance in a wide range of clean energy conversion systems. In this work, several ORR composite electrocatalysts with Co(OH)2 nanosheets deposited on N-doped carbon (Co(OH)2/NC) are comparatively synthesized at room temperature by simple and cost-effective methods using sodium borohydride (NaBH4), ethylene glycol (C2H6O2), and hydrazine hydrate (N2H4) as the reducing agents as well as the metathesis reaction of directly reacting with KOH without a reducing agent. As a result, the Co(OH)2/NC prepared by directly using KOH (Co(OH)2/NC-KOH) displays a higher electrocatalytic activity, methanol tolerance, and stability than the other three. Results of X-ray diffraction (XRD), Raman, transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS) demonstrate that Co(OH)2/NC-KOH has a structure of N-doped carbon-supported β-Co(OH)2 with a Brunauer–Emmett–Teller (BET) surface area of 872 m2/g. This electrocatalytic activity of Co(OH)2/NC comes from a strong synergistic electrocatalysis from N-doped carbon and Co(OH)2 nanosheets. For fundamental understanding, a synergistic ORR electrocatalysis mechanism on Co(OH)2/NC is also proposed in this paper.