Engineering hot carrier dynamics in Ti2CO2 MXene via methane adsorption
Abstract
Hot carrier (HC) dynamics play a crucial role in determining the efficiency of light-driven processes such as photocatalysis, photodetection, and gas sensing. We present a comprehensive first-principles study on the impact of methane (CH4) adsorption on the optoelectronic properties of oxygen-functionalized Ti2CO2 MXene. Using density functional theory (DFT) and real-time time-dependent DFT (rt-TDDFT), we explore how different CH4 adsorption geometries modulate the optical properties. Our results reveal that the bridge configuration is energetically favored by 1.50 eV compared to the on-top site, leading to notable orbital hybridization between CH4 and surface Ti/O atoms. This interaction results in a red-shifted absorption onset and significant enhancement in visible-light absorption. Transition contribution maps and hot carrier analysis further confirm that CH4 molecules at bridge sites actively participate in photoexcitation processes, particularly by increasing hole generation in the valence band. In contrast, the on-top configuration exhibits weak physisorption and negligible optical response. These findings demonstrate the critical role of adsorption geometry in tuning MXene optoelectronics and offer a mechanistic foundation for designing CH4-responsive materials for applications in photocatalysis, gas sensing, and solar energy harvesting.