Theoretical screening of single-atom catalysts (SACs) on MoTiCO MXene for methane activation.

Producing value-added chemicals and fuels from methane (CH) under mild conditions efficiently utilizes this cheap and abundant feedstock, promoting economic growth, energy security, and environmental sustainability. However, the first CH bond activation is a significant challenge and requires high energy. Efficient catalysts have been sought for utilizing CH at low temperatures including emerging single-atom catalysts (SACs). In this work, we screened fourteen transition metals (TM = Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ru, Rh, Pd, Pt) doped at a single oxygen vacancy in MoTiCO (TM-MoTiCO SACs) for methane activation using density functional theory (DFT) calculations. Our results reveal that methane adsorption is thermodynamically stable on all simulated TM-MoTiCO SACs, with the adsorption energies (E) ranging from -0.92 to -0.40 eV. For the CH activation process, Ru-SAC exhibits the lowest activation barrier (E) of 0.22 eV. In summary, Ru-, Rh-, Co-, V-, Cr-, Ti-, and Pt-SACs demonstrate promising catalytic properties for methane activation, with E values below 1.0 eV and an exothermic nature. Our findings pave the way for the design and development of novel single-atom catalysts in MXene materials, applicable not only for methane activation but also for other alkane dehydrogenation processes.