Breaking Symmetry: Enhanced Hydrogen Evolution Reaction Performance of Janus Zr₂COT (T = F, Cl, Br, I) MXenes by Density Functional Theory

This investigation highlights the significant impact of asymmetric Janus Zr 2 COT (T = F, Cl, Br, I) monolayers on enhancing the hydrogen evolution reaction (HER) performance. Employing density functional theory (DFT), our research demonstrates that introducing asymmetric functional groups into Zr 2 COT structures effectively tailors their electronic properties, leading to a marked improvement in HER activity. This structural innovation notably reduces the hydrogen adsorption Gibbs free energy (Δ G H* ) from 0.877 eV for the symmetric Zr 2 CO 2 to below 0.2 eV for the Janus Zr 2 COT configurations, with Zr 2 COBr and Zr 2 COI achieving exceptionally low Δ G H* values of 0.045 and −0.042 eV, respectively, at a hydrogen coverage of 1/4. The monolayers also exhibit remarkable thermal stability and superior electrical conductivity, vital for high-efficiency electrocatalysis. Furthermore, strain engineering underscores the durability of these materials, maintaining Δ G H* values within ±0.2 eV under extensive tensile strain and emphasizing their practical application potential. Crucially, this work uncovers the critical role of electronic structure adjustments in optimizing the HER performance, aligning with the Sabatier principle, and offering fresh perspectives for designing effective, cost-efficient electrocatalysts. In a word, Janus Zr 2 COT monolayers emerge as promising candidates, challenging traditional noble metal catalysts and paving the way for the development of sustainable electrocatalytic materials.