TiO_2纳米管电极上电化学还原CO_2生成CH_3OH  

Electrochemical Reduction of CO_2 to Methanol at TiO_2 Nanotube Electrodes

作　　者：裘建平[1,2] 童怡雯[1] 赵德明[3] 何志桥[1] 陈建孟[1] 宋爽[1] 

机构地区：[1]浙江工业大学环境学院,杭州310032 [2]金华职业技术学院,浙江金华321007 [3]浙江工业大学化学工程学院,杭州310032

出　　处：《物理化学学报》2017年第7期1411-1420,共10页Acta Physico-Chimica Sinica

基　　金：国家自然科学基金(21477117);浙江省自然科学基金(LR14E080001;LQ15E080007;LY15B070005)资助项目~~

摘　　要：采用原位阳极氧化-煅烧法制备TiO_2纳米管(TiO_2NTs)电极,运用X射线衍射(XRD)、电场发射扫描电子显微镜(FESEM)、X射线光电子能谱(XPS)、双电位阶跃测试等对制备电极进行表征,考察了其在0.1mol?L^(-1) KHCO_3水溶液中电化学还原CO_2的催化活性。结果表明TiO_2NTs电极上电化学还原CO_2的主产物为CH_3OH,CH_3OH由HCOOH和HCHO进一步还原而来。电极制备的最佳煅烧温度为450℃(TiO_2NTs-450),电解电位-0.56 V(vs RHE(可逆氢电极))时反应120 min后,生成CH_3OH的法拉第效率和分电流密度分别为85.8%和0.2 m A?cm^(-2)。与550和650℃煅烧的电极相比,TiO_2NTs-450电极具有更高的催化活性,归因于电极表面更多的三价钛活性位,有利于CO_2吸附,从而对·CO_2-起到稳定的作用,速率控制步骤转变为·CO_2-的质子化反应。A series of highly ordered TiO2 nanotube （TiO2NTs） electrodes are prepared via potentiostatic anodization of Ti foil followed by calcining in air. X-ray diffraction （XRD）, field-emission scanning electron microscopy （FESEM）, X-ray photoelectron spectroscopy （XPS）, and potential steps determination are used to characterize the electrodes. The electrochemical reduction of CO2 on these three TiO2NTs electrodes is investigated by cyclic voltammetry and potentiostatic electrolysis in 0.1 moI.L-1 KHCO3 aqueous solution. Methanol is found to be the major product in electrochemical CO2 reduction, while formic acid, formaldehyde, methane, and CO are formed as minor products. Compared with the electrodes sintered at 550 and 650 ℃, the optimal TiO2NTs electrode is found to be the one calcined at 450 ℃ （TiO2NTs-450）. After 120 min of reaction, the Faradaic efficiency and partial current density of methanol is 85.8% and 0.2 mA.cm-2 at -0.56 V vs reversible hydrogen electrode （RHE）, respectively. The trivalent titanium in TiO2 serves as an efficient site for adsorption of CO2 and stabilization of the adsorbed .CO2- radical. Consequently, the reduction of CO2 on TiO2NTs electrodes involves a fast first electron and proton transfer followed by a slow second proton transfer as the rate-limiting step.

关 键 词：TiO2纳米管电极 电化学还原 CO2 甲醇 还原机理 

分 类 号：O621.259.2[理学—有机化学]