Optimized shell thickness of NiSi/SiC core-shell nanowires grown by hot-wire chemical vapour deposition for supercapacitor applications

•The morphology strongly depends on methane (CH4) flow-rate.•High density of nanowires were obtained at CH4 flow-rate of 2.0 sccm.•The highest density and thinnest shell improved supercapacitance performances. In this study, NiSi/SiC core-shell nanowires grown on crystal silicon and Ni foil substrates by hot-wire chemical vapour deposition were extensively investigated. These nanowires were grown by varying the CH4 flow-rate from 0.5 to 3.5 sccm. The nanowires were found to grow at CH4 flow-rates above 0.5 sccm. The structure of the nanowires consisted of a single crystalline NiSi as the core and polycrystalline SiC nanocolumn as the shell. The growth of the NiSi nanowires solely follows a limited nucleation silicide reaction, which is strongly dependent on the growth precursor vapour pressures of SiH4 and CH4 molecules. Increasing the CH4 flow-rate up to 2.0 sccm enhances the growth of high-density vertically aligned nanowires. The electrochemical properties of the NiSi/SiC core-shell nanowire electrodes were also investigated. The NiSi/SiC core-shell nanowire electrode prepared at 2.0 sccm demonstrated the highest electrochemical performance compared with other nanowire electrodes. This nanowire electrode had the highest specific capacitance (234.13 mF/cm2) at the highest scan rate and demonstrated good electrochemical stability (capacity retention of 80 %) at the highest applied current density after 2500 cycles.