Abstract
Atomically dispersed metal-N-C structures are efficient active sites for catalyzing benzene oxidation reaction (BOR). However, the roles of N and C atoms are still unclear. We report a polymerization-regulated pyrolysis strategy for synthesizing single-atom Fe-based catalysts, and present a systematic study on the coordination effect of Fe-NxCy catalytic sites in BOR. The special coordination environment of single-atom Fe sites brings a surprising discovery: Fe atoms anchored by four-coordinating N atoms exhibit the highest BOR performance with benzene conversion of 78.4% and phenol selectivity of 100%. Upon replacing coordinated N atoms by one or two C atoms, the BOR activities decrease gradually. Theoretical calculations demonstrate the coordination pattern influences not only the structure and electronic features, but also the catalytic reaction pathway and the formation of key oxidative species. The increase of Fe-N coordination number facilitates the generation and activation of the crucial intermediate O=Fe=O species, thereby enhancing the BOR activity.
Highlights
Dispersed metal-N-C structures are efficient active sites for catalyzing benzene oxidation reaction (BOR)
An iron-polyphthalocyanine (FePPc) conjugated polymer network (Supplementary Fig. 1) was synthesized by a low-temperature solvent-free solid-phase method in muffle furnace; the polymer network was subjected to pyrolysis at regulated temperatures to afford the Fe-NxCy catalysts with different Fe-N coordination numbers (500 °C for Fe-N4 SAs/N-C, 600 °C for Fe-N3C1 SAs/N-C, and 700 °C for Fe-N2C2 SAs/N-C, in which N-C stands for the N-doped carbon matrix)
Further increasing the pyrolysis temperature to 800 °C led to the formation of Fe3C (Supplementary Fig. 2); after the Fe3C sample was etched with sulphuric acid, Fe nanoparticles were obtained (Supplementary Fig. 3)
Summary
Dispersed metal-N-C structures are efficient active sites for catalyzing benzene oxidation reaction (BOR). We report a polymerization-regulated pyrolysis strategy for synthesizing single-atom Fe-based catalysts, and present a systematic study on the coordination effect of Fe-NxCy catalytic sites in BOR. Dispersed metal-N-C materials, usually synthesized by pyrolysis at different temperatures[22], have been regarded as efficient catalysts for direct catalytic oxidation of benzene to phenol[23]. A systematic investigation of the coordination effect of metalNxCy catalyst is of great significance for understanding the mechanism of catalytic reaction at the atomic level and for guiding the design of more efficient catalysts. We report a polymerization-regulated-pyrolysis (PRP) strategy to fabricate a series of single-atom Fe-based catalysts with different Fe coordination environments, so as to explore the coordination-sensitive reactions based on these atomically dispersed catalysts (Fig. 1). By combining a series of experimental studies and density functional theory (DFT) calculations, we
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
