Mechanistic insights into vacancy-driven activation and dissociation of hydrogen peroxide on Ti3C2O2 MXene in water

Abstract

The rational design of sophisticated oxidation and electrochemical systems depends on an understanding of how hydrogen peroxide (H₂O₂) activates and dissociates on two-dimensional catalysts. Here, using a combination of density functional theory (DFT), nudged elastic band (NEB) calculations, electron localization function (ELF) analysis, and machine-learned interatomic potential molecular dynamics (MLIP-MD) simulations we present a thorough multiscale computational study of the H₂O₂ interaction with pristine and oxygen-deficient Ti₃C₂O₂ MXene. Using the r²SCAN meta-GGA functional, structural and adsorption properties were carefully investigated and compared to hybrid HSE06 and PBE + U simulations. Oxygen vacancies significantly increase surface reactivity by stabilizing firmly bound molecular peroxide intermediates through direct coordination with undercoordinated Ti centers, whereas pristine Ti₃C₂O₂ shows poor molecular adsorption of H₂O₂ without O–O bond activation. In contrast to the artificial overbinding and spontaneous dissociation predicted by PBE + U, r²SCAN offers a balanced description of Ti–O coordination and peroxide intramolecular bonding, according to the electronic structure and ELF analyses. NEB calculations using the MLIP-CHGNet framework reveal an exceptionally low-barrier, stepwise dissociation pathway at oxygen vacancy sites, where peroxide activation is controlled by surface-assisted stabilization instead of direct bond dissociation. The MLIP-MD simulations were run in an explicit aquatic environment at 300 K in order to capture finite-temperature and solvent effects. These simulations show that explicit water molecules and temperature fluctuations greatly speed up peroxide dissociation, facilitate proton transfer, and stabilize reaction intermediates through hydrogen-bond networks, resulting in quick O–O bond cleavage and H₂O production. Together, these findings demonstrate the importance of explicit solvation and finite-temperature dynamics in controlling peroxide reactivity on MXene surfaces and establish oxygen-defective Ti₃C₂O₂ as an effective catalyst for H₂O₂ activation.