二甲醚在Pt电极上吸附和氧化的循环伏安和原位FTIR光谱研究

Electrochemical and In Situ FTIR Studies of Adsorption and Oxidation of Dimethyl Ether on Platinum Electrode

运用电化学循环伏安法(CV)和原位傅立叶变换红外(FTIR)反射光谱,研究了不同pH值溶液中二甲醚(DME)在Pt电极上的解离吸附和氧化过程.稳态CV结果给出,在0.1mol·L-1H2SO4溶液中,当电位处于0.05-0.35V(vsRHE)区间,约70%的Pt表面位被DME的解离吸附产物占据.DME电氧化反应的活性随pH值增加而下降,在0.1mol·L-1NaOH溶液中,氢的吸脱附几乎不受抑制且观察不到明显的氧化电流,表明DME醚键上氧原子的质子化是其发生解离吸附和氧化的必要条件.原位FTIR光谱研究给出DME解离吸附和氧化过程的分子水平信息,指出DME在低电位区间解离生成线型吸附态CO(COL)毒性中间体.当电位高于0.55V(vsRHE)时,COL开始氧化为CO2;在0.75-1.00V(vsRHE)的电位区间则可同时发生经活性中间体(HCOOH)的氧化过程.

Dissociative adsorption and electrooxidation of dimethyl ether （DME） on a platinum electrode in different pH solutions were studied using cyclic voltammetry （CV） and in situ FTIR reflection spectroscopy. The coverage of the dissociative adsorbed species was measured about 70% from hydrogen adsorption-desorption region （0.05-0.35 V（vs RHE）） of steady-state voltammogram recorded in 0.1 mol ·L^-1 H2SO4 solution. It was found that the electrochemical reactivity of DME was pH dependent, i.e., the larger the pH value was, the less the reactivity of DME would be. No perceptible reactivity of DME in 0.1 mol ·L^-1 NaOH solution could be detected. It was revealed that the protonation of the oxygen atom in the C--O--C bond played a key role in the electrooxidation of DME. In situ PTIR spectroscopic results illustrated that linearly bonded CO （COL） species determined at low potential region were derived from the dissociative adsorption of DME and behaved as ＇ poisoning＇ intermediate. The COL species could be oxidized to CO2 at potential higher than 0.55 V （vs RHE）, and in the potential range from 0.75 to 1.00 V （vs RHE） DME was oxidized simultaneously via HCOOH species that were identified as the reactive intermediates.