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

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.