Ionic liquid-TiO2-CuOx composite interfaces combined with gas directional transmission for enhanced electrooxidation of methane to ethanol
Hao Tian, Jie-Tian Yang, Xin Wang, Han Jiao, Zhifeng Gao, Kongying Zhu, Qing He, Zhongli Wang
Abstract
Electrocatalytic oxidation of methane (CH 4 ) to valuable chemicals is an attractive approach to utilize abundant natural gas and renewable electricity. However, the chemical inertness of CH 4 and low solubility in electrolytes result in inferior production rates. Herein, we report ionic liquid-TiO 2 -CuO x composite interfaces combined with gas directional transmission for enhanced electrooxidation of CH 4 to ethanol at ambient temperature and pressure. TiO 2 -CuO x composite catalysts are used as a working electrode , and ionic liquid of 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF 4 ]) aqueous solution as the electrolyte, the composite catalysts achieve a high production rate of ethanol and methanol up to 59.8 mmol g cat −1 h −1 with the total Faradaic efficiency of 84 %. Mechanism studies show that the synergistic effect of [bmim][BF 4 ]-TiO 2 -CuO x enhances the efficiency of CH 4 electrooxidation. [bmim][BF 4 ] not only increases the solubility of CH 4 , but also adsorbs and aggregates on TiO 2 -CuO x surface under the action of anodic potential, and the cation-anion synergy in [bmim][BF 4 ] creates an efficient CH 4 diffusion channel for TiO 2 -CuO x . TiO 2 with Lewis acidity adsorbs and activates CH 4 and CuO x oxidizes water to produce hydroxyl radicals (∙OH). TiO 2 -CuO x synergistically oxidize CH 4 to generate a series of intermediates (*CH 3 , *OCH 3 , *OCH 2 and *OCH 2 CH 3 ), while [bmim][BF 4 ] can stabilize the intermediates and promote ethanol generation and desorption.