Design of Atomic Ordering in Mo<sub>2</sub>Nb<sub>2</sub>C<sub>3</sub>T<sub><i>x</i></sub> MXenes for Hydrogen Evolution Electrocatalysis.

Wyatt, Brian C; Thakur, Anupma; Nykiel, Kat; Hood, Zachary D; Adhikari, Shiba P; Pulley, Krista K; Highland, Wyatt J; Strachan, Alejandro et al. · Nano Lett · 2023

basic_science · Level V

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Abstract

The need for novel materials for energy storage and generation calls for chemical control at the atomic scale in nanomaterials. Ordered double-transition-metal MXenes expanded the chemical diversity of the family of atomically layered 2D materials since their discovery in 2015. However, atomistic tunability of ordered MXenes to achieve ideal composition-property relationships has not been yet possible. In this study, we demonstrate the synthesis of Mo<sub>2+α</sub>Nb<sub>2-α</sub>AlC<sub>3</sub> MAX phases (0 ≤ α ≤ 0.3) and confirm the preferential ordering behavior of Mo and Nb in the outer and inner M layers, respectively, using density functional theory, Rietveld refinement, and electron microscopy methods. We also synthesize their 2D derivative Mo<sub>2+α</sub>Nb<sub>2-α</sub>C<sub>3</sub>T<sub><i>x</i></sub> MXenes and exemplify the effect of preferential ordering on their hydrogen evolution reaction electrocatalytic behavior. This study seeks to inspire further exploration of the ordered double-transition-metal MXene family and contribute composition-behavior tools toward application-driven design of 2D materials.