CO oxidation on MXene(Mo_(2)CS_(2)) supported single-atom catalyst: A termolecular Eley-Rideal mechanism

Finding transition metal catalysts for effective catalytic conversion of CO to CO_(2)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 (Mo_(2)CS_(2)) 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 Mo_(2)CS_(2)monolayer.Three likely reaction pathways,LangmuirHinshelwood (LH),Eley-Rideal (ER),and Termolecular Eley–Rideal (TER) for CO oxidation on the Ru1-and Ir_(1)@Mo_(2)CS_(2)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-Ru_(1)-OCO) and formation of OCO-Ir_(1)-OCO intermediate.The downshift d-band center of Ru1-and Ir_(1)@Mo_(2)CS_(2)help to enhance activity and improve catalytst stability.Moreover,a microkinetic study predicts a maximum CO oxidation rate of 4.01×10^(2)s^(-1)and 4.15×10^(3)s^(-1)(298.15K) following the TER pathway for the Ru_(1)-and Ir_(1)@Mo_(2)CS_(2)catalysts,respectively.This work provides guideline for fabricating and designing highly efficient SACs with superb catalyts using MXene materials.

Non-noble metal single-atom catalyst of Co_(1)/MXene(Mo_(2)CS_(2))for CO oxidation

MXene is a variety of new two-dimensional(2D)materials with early transition metal carbides,nitrides,and carbonitrides.Quantum chemical studies have been carried out on the geometries,electronic structures,stability and catalytic properties of a non-noble metal single-atom catalyst(SAC)with single Co atom anchored on MXene materials of Mo_(2)CS_(2).The Co adatom anchored on top of the Mo atom of this MXene is found to be rather stable,and this SAC is appropriate for CO oxidation.The charge transfers from the surface to the adsorbed CO and O2 play a significant role in the activation of these molecules on Co_(1)/Mo_(2)CS_(2).With this catalyst,the Eley-Rideal(ER),Langmuir-Hinshelwood(LH),and Termolecular Eley-Rideal(TER)mechanisms are explored for CO oxidation.We find that,while all the three mechanisms are feasible at low temperature,Co_(1)/Mo_(2)CS_(2) possesses higher catalytic activity for CO oxidation through the TER mechanism that features an intriguing OC(OO)CO intermediate(IM)adsorbed on Co single atom.The calculated activation energy barriers of the rate-limiting step are 0.67 eV(TER),0.78 eV(LH)and 0.88 eV(ER),respectively.The present study illustrates that it is promising to develop and design low-cost,non-noble metal SACs using MXene types of 2D materials.