The Electrochemical Properties of Iron Diselenide Hedgehog Particles

Abstract

The exceptional charging capacity of colloidal semiconductor nanoparticles has garnered increasing attention from some researchers. This dissertation aims to expand the charging capacity from nanoparticles to nanoparticle assemblies, focusing on utilizing the high surface corrugation and complex geometric features of iron diselenide hedgehog particles (FeSe2 HPs) to understand better their electrochemical properties and find an electrolyte system suitable for further studies. Cyclic Voltammetry (CV) experiments were first performed to select the best combination (solvent, supporting electrolyte, and working electrode) for the electrolyte system to fully utilize the electrochemical activities of FeSe2 HPs. The system of FeSe2 HPs with 0.1 M lithium trifluoromethanesulfonate (LiTf) in N,N-dimethylformamide (DMF) using a gold disk working electrode stood out and will be applied for further studies. This electrolyte system was discovered to be electrochemically stable for a long-term CV test up to 4 hours, and the hedgehog structure remained intact throughout the course of the electrochemical experiment. CV of FeSe2 HPs indicated an oxidation peak related to FeSe2, and bulk electrolysis plot along with density functional perturbation theory (DFPT) calculations both demonstrate a high number in the magnitude of 10^8 positive charges stored per single HP, which is the largest number reported to date in the perspective of charging capacity per nanoparticle assemblies. The charging capacity of FeSe2 HPs in this electrolyte system surpassed other previously studied colloidal semiconductor nanoparticles in many aspects including charges per surface area of a single particle, per volume of a single particle, and per crystalline unit cell. X-ray Photoelectron Spectra showed that mostly the selenium atoms will be oxidized during the bulk oxidation of FeSe2 HPs. Due to the great electrochemical properties of FeSe2 HPs, they have the potential to be utilized as ‘dispersed’ heterogeneous electrocatalysts in many heterogeneous electrocatalytic systems.