First-principles Studies of Two-dimensional MXene Materials for Energy Storage Systems

Abstract

This thesis has guiding significance for the structural design and the development of next-generation high-energy density cathode materials. Recent research has underscored the pivotal role of two-dimensional (2D) transition metal carbides/nitrides (MXene) materials in advancing various energy storage technologies, particularly in the realms of halogen anion batteries (HABs), aqueous proton batteries, and hydrogen storage. MXenes, with their unique properties and structures, have emerged as promising candidates for electrode materials, offering potential solutions to key challenges in energy storage.

In one study, MXenes were explored as electrodes for HABs, which are considered promising alternatives to traditional metal-ion batteries (MIBs) due to their high abundance, energy density, and safety. Through first-principles calculations, we investigated the adsorption, stability, diffusion, and electrochemistry properties of four halogen anions (F^-, Cl^-, Br^-, and I^-) on nine different M₂CT₂ (M = Ti, Zr, Hf; T = O, H, OH) MXenes. The results identified several highly stable HAB models with optimal diffusivity and electrochemical performance on MXene electrodes. Notably, MXene-based electrodes exhibited excellent theoretical capacity, attractive open-circuit voltage, and minimal voltage changes, thus demonstrating their potential for HAB applications.

In another study, MXene electrodes were explored in the context of aqueous proton batteries, where challenges such as the hydrogen evolution reaction (HER) and proton transport mechanism needed to be addressed. Here, we developed a general interpretable descriptor for HER and capacity performance, enabling the design of high-performance MXene proton batteries. By decoupling the proton transport mechanism in a solution-interface-electrode model, the results revealed insights into the kinetic process and highlighted the importance of MXene charges in facilitating faster proton transfer rates. This work not only advances the understanding of MXene-based proton batteries but also provides a framework for designing efficient energy storage systems across various applications.

Overall, the collective findings highlight MXene materials' versatility and potential in revolutionizing energy storage technologies, paving the way for further advancements in battery and hydrogen storage applications.

Date of Award	27 Aug 2024
Original language	English
Awarding Institution	City University of Hong Kong
Supervisor	Jun FAN (Supervisor)