Synthesis and Optimization of Specific Ferrites-Transition Metal Dichalcogenides Nanocomposites for Enhanced Electrochemical Energy Storage

Abstract

This PhD dissertation focuses on the synthesis and optimization of ferrite–transition metal dichalcogenide nanocomposites, specifically MoS2/ZnFe2O4, for enhanced electrochemical energy storage. MoS2 Nanosheets (NS) were prepared using a green liquid-phase exfoliation method and directly integrated onto Ni foam without binders or conductive additives. These NS demonstrated superior electrochemical performance, achieving a specific capacitance of 985 F/g at 8 A/g, supported by Density Functional Theory (DFT) simulations that revealed reduced potassium ion diffusion barriers and improved charge transfer.
ZnFe2O4 Nanoparticles (NPs) were synthesized via a hydrothermal route, with particle size tuned from 476 to 49 nm by adjusting surfactant concentration. The optimized NPs delivered a high capacitance of 1819.6 F/g at 10 A/g and exhibited excellent cycling stability (107.7% retention after 2500 cycles). Enhanced performance was linked to increased surface area, oxygen vacancies, and magnetic property improvements. Lorentz Transmission Electron Microscopy (TEM) provided direct evidence of magnetic domain structures and domain wall movement, offering further insight into the nanoscale magnetic landscape associated with oxygen vacancy formation. In addition, in-situ gas TEM investigations under CO2 and Ar atmospheres revealed dynamic d-spacing fluctuations, highlighting the structural reactivity of ZnFe2O4 at the atomic level under gaseous environments.
A hybrid MoS2/ZnFe2O4 Nanocomposites (NCs) were further engineered using a hydrothermal synthesis strategy. The optimized 1:1 molar ratio composite achieved a capacitance of 2076.9 F/g at 25 A/g and retained 94.3% after 2500 cycles. DFT calculations confirmed that the heterostructure interface introduced new energy states near the Fermi level, enhancing conductivity and storage capability. Overall, this work demonstrates how nanostructure design, defect engineering, and heterostructure formation collectively advance the performance of next-generation energy storage materials.

Date of Award	2025
Original language	American English
Supervisor	Dalaver Hussain Anjum (Supervisor)