Selective CH<sub>4</sub> Partial Photooxidation by Positively Charged Metal Clusters Anchored on Carbon Aerogel under Mild Conditions
Kai Zheng, Yang Wu, Zexun Hu, Xingchen Jiao, Li Li, Yuan Zhao, Shumin Wang, Shan Zhu, Wenxiu Liu, Wensheng Yan, Yongfu Sun, Yi Xie
Abstract
Selective partial photooxidation of CH4 into value-added chemicals under mild conditions still remains a huge bottleneck. Herein, we design positively charged metal clusters anchored on a three-dimensional porous carbon aerogel. With 0.75FeCA800-4 as an example, X-ray photoelectron spectra and Raman spectra disclose that the iron sites are positively charged. In situ electron paramagnetic resonance spectra show that the Feδ+ sites could donate electrons to activate CH4 into CH4– by virtue of the excited-state carbon atoms; meanwhile, they could convert H2O2 into •OH radicals under irradiation. In addition, in situ diffuse Fourier-transform infrared spectra suggest the CH3OOH obtained is derived from CH4 oxidation by the hydroxylation of *CH3 and *CH3O intermediates. Consequently, 0.75FeCA800-4 displays a CH3OOH selectivity of near 100% and a CH3OOH evolution rate of 13.2 mmol gFe–1 h–1, higher than those of most previously reported supported catalysts under similar conditions.