resumo
Through density functional theory calculations, the mechanism of CO oxidation to CO2 on single-atom catalysts consisting of an atom of Ti, Fe, or Zn deposited on the surface of the Mo2CO2 MXene is investigated. In the case of Fe@Mo2CO2, a mechanism resembling that of Termolecular Langmuir-Hinshelwood (TLH) is thermodynamically and kinetically favored, displaying very exothermic CO2 formation, low activation energies, and easy CO2 desorption. On Ti@Mo2CO2, the dissociation of CO2 is almost barrierless and much more likely to occur than CO2 desorption, barring the usage of this surface as a catalyst for CO oxidation. Finally, on Zn@Mo2CO2, a hybrid Langmuir-Hinshelwood/Eley-Rideal (LH/ER) mechanism is thermodynamically and kinetically feasible. Here, after the first CO2 forms, with an energy barrier of only 0.62 eV, the second CO2 is formed spontaneously, and the Zn-CO2 interactions are weak enough to allow desorption. The calculated thermodynamic quantities and reaction rates at T = 300 K indicate that Fe@Mo2CO2 should be quite active toward CO oxidation, followed by Zn@Mo2CO2, while the Ti-based model is inactive. The results add to the evidence that establishes single transition metal atoms adsorbed on MXene surfaces as cheap and easily obtainable catalysts that offer the best of both bare and functionalized MXenes.
palavras-chave
FINDING SADDLE-POINTS; ELASTIC BAND METHOD
categoria
Science & Technology - Other Topics
autores
Gouveia, JD; Gomes, JRB
nossos autores
José Daniel Lago da Silva Neves Gouveia
Investigador Auxiliar
José R. B. Gomes
Investigador PrincipalProjectos
CICECO - Aveiro Institute of Materials (UIDB/50011/2020)
CICECO - Aveiro Institute of Materials (UIDP/50011/2020)
Associated Laboratory CICECO-Aveiro Institute of Materials (LA/P/0006/2020)
MXenes catalysts for the water gas shift reaction (ForTheShift)
agradecimentos
This work was developed within the scope of the projects CICECO-Aveiro Institute of Materials, with refs. UIDB/50011/2020, UIDP/50011/2020 and LA/P/0006/2020, and ForTheShift, with ref. 2022.02949.PTDC, financed by national funds through the FCT/MEC (PIDDAC). The authors are also thankful to FCT I.P. for the computational resources granted in the framework of project ref. 2022.15802.CPCA.A2 by the FCT/CPCA/2022/01 Call for Advanced Computing Projects. JDG thanks the Portuguese Foundation for Science and Technology (FCT) through the grants with refs. 2022.00719.CEECIND and 2023.06511.CEECIND, in the scope of the Individual Calls to Scientific Employment Stimulus-5th and 6th Editions.