Electrochemical phase evolution of NiCo2S4 nanoparticles in aqueous alkaline electrolyte

Abstract

Evaluating structural stability of electrode materials under electrochemical operation in the alkaline electrolyte needs to further clarify, which is closely related with the electrochemical mechanism. Herein, NiCo2S4 nanoparticles@CNT sponge was prepared as the working electrode in three-electrode test system. From the first 20th CV test procedure, specific capacitances with the range of 1034 ∼ 1344F/g show electrochemical reversibility. Intriguingly, NiCo2S4 nanoparticles have not only stacked into nanosheets, and but also separated from the surface of the CNT sponge. Spinel NiCo2S4 nanoparticles have first partially cracked into the metastable derivative phases of Ni(Co)OOH, Ni(OH)2, and then quickly converted into the mixed hexagonal NiOOH and cubic Co3S4. S atoms disengage from the lattice positions of spinel NiCo2S4 nanoparticles, which depicts the irreversible electrochemical reaction occurring during electrochemical operation process.