DFT Investigation of Transition Metal (Fe, Co, and Ni)-Doped Zr2CO2 MXenes for High-Performance H2, CH4, and CO2 Gas Sensing

High-performance gas-sensing materials play an important role in industrial production, environmental monitoring, and biomedical applications. Two-dimensional MXene-based materials have attracted increasing attention for gas sensing because of their layered structures, high electrical conductivities, abundant surface functional groups, and large specific surface areas. In this study, density functional theory calculations based on the PBE-D3 method were performed to systematically investigate the adsorption behavior of H2, CH4, and CO2 on pristine and transition metal-doped Zr2CO2 MXenes. The effects of Fe, Co, and Ni doping on the adsorption energies, charge transfer, electronic structures, ELF, COHP, variations in band gap, work function modulation, electronic sensitivity parameter, and adsorption mechanisms were evaluated. The results show that transition metal doping can markedly enhance the gas-sensing properties of Zr2CO2 MXene. Among the investigated systems, Co-doped Zr2CO2 exhibited the most favorable sensing performance toward H2, CH4, and CO2, which can be attributed to the doping-induced modulation of the electronic structure, increased active adsorption sites, and improved charge transfer pathways. These findings provide theoretical guidance for the rational design of transition metal-doped MXene materials for high-performance gas sensing and suggest that Co-doped Zr2CO2 is a promising candidate for detecting H2, CH4, and CO2.