CBE Doctoral Dissertation Defense: “Tailoring MXene Chemistry through Composition and Undercoordination for Applications in Hydrogen Chemistries” (Yamilée Morency)

Abstract:

Global transition to clean energy relies on the development of efficient hydrogen storage materials and hydrogen evolution reaction (HER) catalysts—two primary chemistries investigated in this thesis. MXenes, a family of two-dimensional transition metal carbides and nitrides, have emerged as promising candidates for hydrogen technologies due to their high electrical conductivity, chemical tunability, and structural versatility. Yet, the mechanisms by which their chemical composition and morphology—particularly atomic coordination environments—influence performance in hydrogen-related chemistries remain insufficiently understood.

This work employs atomic-scale high-throughput modeling, primarily based on density functional theory (DFT), to systematically investigate how compositional tuning and under-coordination affect hydrogen adsorption and catalytic activity across a wide range of MXene structures. The role of under-coordination is probed through the modeling of MXene nanoribbons and nanoparticles, revealing that edge environments significantly impact hydrogen adsorption, with certain configurations exhibiting enhanced catalytic activity relative to basal planes.

The study further explores the chemistry and HER performance of representative MXenes, including Mo₂TiC₂O₂ and other double-transition-metal systems, and identifies key structural and electronic features governing their behavior. The results demonstrate that both composition and under-coordination are powerful levers for optimizing MXenes in hydrogen storage and HER applications. By establishing structure–property relationships and uncovering relevant electronic descriptors, this thesis provides guidance for the design of MXene-based hydrogen technologies. These findings support the development of low-cost, earth-abundant alternatives to platinum catalysts and contribute to the broader effort of enabling sustainable hydrogen solutions through computational materials discovery.