CO oxidation on MXene (Mo2CS2) supported single-atom catalyst: A termolecular Eley-Rideal mechanism

Finding transition metal catalysts for effective catalytic conversion of CO to CO2 has attracted much attention. MXene as a new 2D layered material of early transition metal carbides, nitrides, and carbo-nitrides is a robust support for achoring metal atoms. In this study, the electronic structure, geometries, thermodynamic stability, and catalytic activity of MXene (Mo2CS2) supported single noble metal atoms (NM = Ru, Rh, Pd, Ir, Pt and Au) have been systematically examined using first-principles calculations and ab initio molecular dynamic (AIMD) simulations. First, AIMD simulations and phonon spectra demonstrate the dynamic and thermal stabilities of Mo2CS2 monolayer. Three likely reaction pathways, Langmuir-Hinshelwood (LH), Eley-Rideal (ER), and Termolecular Eley–Rideal (TER) for CO oxidation on the Ru1- and Ir1@Mo2CS2 SACs, have been studied in detail. It is found that CO oxidation mainly proceeds via the TER mechanism under mild reaction conditions. The corresponding rate-determining steps are the dissociation of the intermediate (OCO-Ru1-OCO) and formation of OCO-Ir1-OCO intermediate. The downshift d-band center of Ru1- and Ir1@Mo2CS2 help to enhance activity and improve catalytst stability. Moreover, a microkinetic study predicts a maximum CO oxidation rate of 4.01 × 102 s-1 and 4.15 × 103 s-1 (298.15 K) following the TER pathway for the Ru1- and Ir1@Mo2CS2 catalysts, respectively. This work provides guideline for fabricating and designing highly efficient SACs with superb catalyts using MXene materials.