Preparation of Magnetically Driven Nickel Phosphide Nanowires and Their Electrochemical Properties

Hye-Won Kim,Heon-Cheol Shin

doi:10.3390/app12010049

Abstract

In this study, nickel phosphide nanowires with various structures and compositions were fabricated for the first time via magnetically-assisted liquid phase synthesis. The curvature and aspect ratio of the nanowires largely depended on the strength of the magnetic field applied during synthesis. Their phosphorus content together with the morphology were significantly modified according to the pH and reducing agent concentration. Nanowires with different structures and phosphorus contents were preliminarily tested for their capabilities to serve in general electrochemical applications. The degree of reaction (i.e., amount of reaction charge) increased with increases in the reaction area and phosphorus content of the nanowires. The rate characteristics of the reaction showed a peculiar increasing trend for a small reaction surface area and low phosphorus content. A change in the ohmic overpotential according to the nanowire curvature (aspect ratio) and porosity was suggested to be the reason for this unusual trend. Electrodes with high phosphorus contents or high reaction surface areas rapidly deteriorated during repetitive redox reactions. Based on the results for the degradation degree, the effect of the reaction surface area dominated that of the phosphorus content in the deterioration of the nickel phosphide nanowires.

Highlights

Transition metal phosphides have beneficial physical, chemical, and mechanical properties owing to their excellent electronic conductivity [1] and stability in acidic and alkaline conditions [2], as well as a high melting point, hardness, and abrasion resistance [3]
We present our preliminary results on nickel phosphide nanowires with various structures and compositions, prepared by liquid phase synthesis in a magnetic field
Nanowires with highly uniform diameters and high aspect ratios grew under a high magnetic field

Summary

Introduction

Transition metal phosphides have beneficial physical, chemical, and mechanical properties owing to their excellent electronic conductivity [1] and stability in acidic and alkaline conditions [2], as well as a high melting point, hardness, and abrasion resistance [3]. There have been many studies to apply these compounds to engineering applications, and nickel phosphides have emerged as notable candidates [4,5,6,7]. Many studies have been conducted to improve the output and efficiency of electrochemical devices by fabricating electrodes using nanomaterials. Because such electrodes possess a large surface area, the surface reaction resistance is significantly reduced. Nickel phosphide nanomaterials are synthesized by various methods, such as pyrolysis of organometallic precursors [14,15], high-temperature reduction [16,17], solid-state phase transformation [18], and the vapor–liquid–solid (VLS) method [19,20]

Methods

Results

Conclusion