Regulating the electronic structure through charge redistribution in dense single-atom catalysts for enhanced alkene epoxidation

Abstract

Inter-site interaction in densely populated single-atom catalysts has been demonstrated to have a crucial role in regulating the electronic structure of metal atoms, and consequently their catalytic performances. We herein report a general and facile strategy for the synthesis of several densely populated single-atom catalysts. Taking cobalt as an example, we further produce a series of Co single-atom catalysts with varying loadings to investigate the influence of density on regulating the electronic structure and catalytic performance in alkene epoxidation with O2. Interestingly, the turnover frequency and mass-specific activity are significantly enhanced by 10 times and 30 times with increasing Co loading from 5.4 wt% to 21.2 wt% in trans-stilbene epoxidation, respectively. Further theoretical studies reveal that the electronic structure of densely populated Co atoms is altered through charge redistribution, resulting in less Bader charger and higher d-band center, which are demonstrated to be more beneficial for the activation of O2 and trans-stilbene. The present study demonstrates a new finding about the site interaction in densely populated single-atom catalysts, shedding insight on how density affects the electronic structure and catalytic performance for alkene epoxidation.

Electrochemical Potential-Driven Shift of Frontier Orbitals in M–N–C Single-Atom Catalysts Leading to Inverted Adsorption Energies

“…To validate the discussion, we take the Co/N–C SAC as an example to illustrate the energy level changes in the central Co atom. , As presented in Figure , the energy level of the Dirac point at the PZC sits marginally above the Fermi level. The Co atom exhibits spin polarization with one unpaired d xz electron, and the PZC lies at about −0.36 V vs SHE, aligning with previous studies …”

An Overview of Metal Density Effects in Single-Atom Catalysts for Thermal Catalysis

“…DFT calculations revealed a positive correlation between electron transfer and intersite distance of SACs, where the emerged electron redistribution effect was continuously weakened as the distance elongated. Cao et al 59 prepared a series of Co SACs to understand the influence of single-atom density on the electronic structures. As the density of Co sites increased, the whole support became more chargeconnected, resulting in charge redistribution that in turn accumulated more charge on densely populated Co SACs.…”

“…In addition, Cao et al 59 revealed the electronic structure of the metal center in densely populated SACs. To correlate the single-atom density with metal loading, they prepared a series of Co SACs ranging from 5.4 to 21.2 wt % (Figure 9f).…”

“…The key factor is to create abundant anchoring sites and a strong metal–support interaction. As shown in Figure , we also summarized the representative breakthrough results reported in the literature about densely populated SACs for different thermal catalytic reactions, such as selective hydrogenation, CO 2 hydrogenation, coupling reactions, alkene epoxidation, and Fenton-like reactions. ,,− ,,,,,,,− In the following section, we give detailed examples and analyze how single-atom density affects the electronic structure and catalytic performance in different kinds of reactions.…”

“…The inset shows the configurations of intermediates of 4-Co 1 –N 3 O 1 . Panels (f–k) were reproduced with permission from ref . Copyright 2023 Springer Nature.…”