Preparation and electrochemical properties of Co–Si 3N 4 nanocomposites

Abstract

Cobalt nanoparticles on an amorphous Si 3N 4 matrix were synthesized by direct ball-milling of Co and Si 3N 4 powders for an improvement of their electrochemical performance. The microstructure, morphology and chemical state of the ball-milled Co–Si 3N 4 composites are characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The electrochemical performance of Co–Si 3N 4 composites was investigated by galvanostatic charge–discharge process and cyclic voltammetry (CV) technique. It is found that metallic Co nanoparticles of 10–20 nm in size are highly dispersed on the amorphous inactive Si 3N 4 matrix after the ball-milling. The composite with a Co/Si molar ratio of 2/1 shows the optimized electrochemical performance, including discharge capacity and cycle stability. The formation of Co nanoparticles with a good reaction activity is responsible for the discharge capacity of the composites. The reversible faradic reaction between Co and β-Co(OH) 2 is dominant for ball-milled Co–Si 3N 4 composite. The surface modification of the hydrogen storage PrMg 12–Ni composites using Co–Si 3N 4 composites can enhance the initial discharge capacity based on the hydrogen electrochemical oxidation and Co redox reaction.