Evidence for Spin Polarization and Lattice Oxygen Migration During Cyclohexane Oxidation Over CoOx/Fe2O3
Evidence for Spin Polarization and Lattice Oxygen Migration During Cyclohexane Oxidation Over CoOx/Fe2O3
研究概述
在Fe2O3纳米棒上通过原子层沉积引入CoOx团簇，形成Co—O—Fe界面，以自旋极化及晶格氧迁移促进氧活化和界面限域自由基转化。无溶剂环己烷氧化中转化率14.6%，环己醇/环己酮选择性82.7%，质量归一反应速率830.7 mmol·g催化剂⁻¹·h⁻¹。
谱图与表征信息
FIGURE 3 Co-induced spin state reconstruction of surface Fe sites. (a) Superconducting quantum interference device (SQUID) analysis of the FeNR and 5Co/FeNR. (b) 1/χ versus temperature plot of the FeNR and 5Co/FeNR, with calculated μeff values. (c) Co L–edge soft X-ray absorption spectroscopy (sXAS) spectra of 5Co/FeNR. The experimental data are deconvoluted into contributions from Co t2g orbitals (blue curve) and Co eg orbitals (pink curve) species. (d) Fe L–edge sXAS spectra of 5Co/FeNR and FeNR. (e) Fe X-ray emission (XES) spectra of 5Co/FeNR and FeNR. (f) X-ray absorption near-edge structure (XANES) spectra of 5Co/FeNR and 10Co/FeNR as well as Co foil, CoO foil and Co2O3 foil references at the Co K-edge. (g) Microscopic mechanism of the surface Fe atom’s spin-state reconstruction.
FIGURE 5 Enhanced lattice oxygen migration. 18O2 isotope labeling experiment of (a) FeNR and (b) 5Co/FeNR. (c) In situ isotopic infrared spectroscopy of 5Co/FeNR showed the vibration of the key intermediate species. (d) Synchrotron radiation photoionization mass spectrometry (SR- PIMS) showed the cyclohexyl peroxyl radical (C6H11OO⋅). (e) XANES spectra of the FeNR and 5Co/FeNR at O K-edge. (f) Effect of radical scavengers (TBA and PBQ at 1 mM) on the 5Co/FeNR and FeNR, respectively. (g) In situ EPR showed the key radical intermediates of 5Co/FeNR. Detection of radical intermediates by SR-PIMS for (h) 5Co/FeNR and (i) FeNR.