Non-noble metal single-atom catalysts with phosphotungstic acid (PTA) support: A theoretical study of ethylene epoxidation

Abstract

Geometric and electronic structures of phosphotungstic acid (PTA) supported single transition metal atom (Fe, Co, Ni, Ru, Rh, Pd, Os, Ir and Pt) catalysts have been systematically investigated by using the first-principles theoretical methods. Possible reaction mechanism for ethylene epoxidation was explored. The most possible anchoring site for the single transition metal atom is the fourfold hollow site on PTA. As the non-noble metal Fe 1 -PTA system possesses considerable adsorption energies towards both O 2 and C 2 H 4 , the strong bonding interaction between Fe 1 and PTA cluster was analyzed. It is found that the electron transfers from Fe atom to PTA cluster and strong covalent metal-support interactions (CMSI) between the Fe 3d orbitals and O 2p orbitals of PTA lay the foundation of high stability. The proposed catalytic reaction mechanism for ethylene epoxidation on Fe 1 -PTA single-atom catalyst (SAC) includes three steps: the O 2 adsorbs on Fe 1 -PTA via electron transfer; the first ethylene attacks the adsorbed O 2 molecule on Fe 1 -PTA followed by the formation of C 2 H 4 O; finally, the O atom remained on Fe 1 -PTA reacts with a second ethylene to form the product and accomplish the catalytic cycle. The Fe 1 -PTA has high selectivity and catalytic activity for ethylene epoxidation via an Eley-Rideal mechanism with low energy barriers. A potentially competitive pathway for the formation of acetaldehyde is not kinetically favorable. These results provide insights for the development of highly efficient heterogeneous SACs for ethylene epoxidation with non-noble metals.

Non-noble metal single-atom catalyst of Co1/MXene (Mo2CS2) for CO oxidation

“…1a. It is found that the Co atom preferred to stay at the energetically most stable site, located above the Mo atoms (Site I) with the binding energy of −3.46 eV, which is around one third of the Co atom's binding energy to phosphotungstic acid (PTA) support [91]. The Co atom is bonded with the three neighboring S atoms, all having equal Co-S bond distance of 2.08 Å.…”

Theoretical studies of MXene-supported single-atom catalysts: Os1/Ti2CS2 for low-temperature CO oxidation

“…Over the past decade, SAC has expanded rapidly and the concept of SAC has been further developed into dynamic SACs [24] and single-cluster catalysts (SCCs) [25,26]. Many studies [27][28][29][30][31][32][33][34][35][36] have been devoted to obtaining SACs with high stability, high selectivity and high reactivity [37][38][39] for thermocatalysis, photocatalysis, electrocatalysis, and photoelectrocatalysis reactions [15,[40][41][42][43], such as CO oxidation, water gas shift reaction, activation of C-H bonds, photo-and electro-catalytic water splitting, and CO 2 reduction reaction, oxygen reduction reaction, hydrogen evolution reaction, oxygen evolution reaction, hydrogenation reactions, and nitrogen reduction reaction [5,15,[43][44][45][46][47][48][49][50][51][52][53][54].…”

Polyoxometalate-based materials: quasi-homogeneous single-atom catalysts with atomic-precision structures

“…In 2020, another first-principles study on PW 12 -supported SACs (Fig. 1c) for catalytic ethylene epoxidation was reported by Li et al 34 The DFT calculation results demonstrate the lower absorption energy of O 2 on the Fe 1 –PW 12 cluster compared with ethylene (Fig. 3a), by which Fe 1 –PW 12 may exhibit higher catalytic activity.…”