Single-atom catalysts on ceria substrates: Exploring cluster and surface effects on methane activation

Author(s)

Moraes, Pedro Ivo R. ; Peraca, Carina S. T. ; Da Silva, Juarez L. F.

• Document type: Journal article
• Source: MOLECULAR CATALYSIS; v. 564, p. 10-pg., 2024-06-24.

Abstract

The activation of methane (CH 4 ) is a critical step in its conversion to high value products, which require the use catalysts due to the higher stability of the C -H bond. In this study, we combined density functional theory calculations and the unit bond index -quadratic exponential potential approximation to investigate the first CH 4 dehydrogenation in the TM/(CeO 2 ) 10 system, where TM represents a single transition -metal specie (Fe, Co, Ni, Cu) supported in the compact (CeO 2 ) 10 cluster. In addition, substrate size effects will be addressed by comparing our results with previous surface science studies by our group. We found a direct correlation between the magnitude of the TM adsorption energy on the CeO 2 substrates (hollow and bridge sites) and the magnitude of charge transfer from the TM adatoms to the substrates, while CH 4 has a weaker physisorption binding energy to the ceria cluster and the surface substrates. Molecular fragments derived from CH 4 (CH 3 and H) bind through chemisorption interactions to the TM and O sites, respectively. The estimated energy barrier for the cleavage of the C -H bond is lower when the reaction occurs in the cluster rather than on the surface. The molecular fragments exhibited better stabilization on cluster substrates, resulting in an exergonic dehydrogenation reaction; whereas, for surfaces, the reaction was endergonic. Among the selected TM species, Fe and Co adatoms are promising candidates for the first CH 4 dehydrogenation on CeO 2 substrates, which can be explained by the magnitude of the metal -support interaction and stabilization of the CH 3 specie, which results in the lowest barriers among the evaluated transition metals. (AU)

• FAPESP's process: 21/03357-3 - Computational study of methane conversion in new products using cerium oxide-based catalysts
• Grantee: Carina de Souza Teixeira Peraça
• Support Opportunities: Scholarships in Brazil - Doctorate
• FAPESP's process: 23/12824-0 - Catalyst Screening for Electrochemical Water Splitting based on Computational Material Design Techniques
• Grantee: Pedro Ivo Rodrigues Moraes
• Support Opportunities: Scholarships in Brazil - Post-Doctoral