Acid- and Alkaline-Induced Phase and Structure Reconstruction of Nickel Sulfide Toward Enhanced Electrochemical Performance

Abstract

Nickel sulfides prepared by conventional methods usually exhibit bulk structure and multiple phases, which poses great challenges for controllably synthesizing designer particles with high performance. Herein, we developed a novel and universal strategy to achieve phase and structure reconstruction of nickel sulfide by an acid- or alkaline-induced strategy. Interestingly, we found that the HCl and KOH could partially extract nickel and sulfur from nickel sulfide under a hydrothermal process, respectively. As a result, HCl treatment induces the transformation of nickel sulfide from nickel-rich phase (NiS) to nickel-deficient phase (NiS2) and bulk structure to micro-nano structure. The KOH treatment droves the transformation of nickel sulfide from sulfur-rich phase (NiS2) to sulfur-deficient phase (NiS), as well as the changes in surface microstructure. Attributed to the structural advantages brought by structure reconstruction, these samples after treatment exhibit enhanced electrochemical properties. This is a unique and significant finding to structure-regulation method of transition metal sulfides and will enrich their structure-dependent applications.

Keywords: nickel sulfides, crystal phase, structure reconstruction, electrochemical performance