酸性介质中1,2-丙二醇在铂电极上吸附和氧化过程的原位FTIR反射光谱研究

应用电化学循环伏安和原位FTIR反射光谱研究1,2-丙二醇在Pt电极上吸附和氧化过程。结果指出1,2-丙二醇的电氧化可按双途径进行。其一经1,2-丙二醇在Pt上解离吸附产物氧化至CO_2。但在较低电位下这些解离吸附产物(红外检测为CO_(ad)、[﹥C=CH_2]_(ad)等)累积吸附于电极上, 毒化Pt表面抑制其它反应。当电位大于0.3 V后它们一经生成即氧化脱附, 从而使1,2-丙二醇得以在未毒化Pt表面经反应中间体氧化至CO_2。在实验条件下,原位FTIR反射光谱检测到的反应中间体可能有HOC-CHOHCH_3(或CH_2OHCOCH_3)和HOOC-COCH_3(或HOOC-CHOHCH_3)等物种。

IN-SITU FTIR Studies on Adsorption and Oxidation of 1,2-Propanediol at a Platinum Electrode in Acid Solutions

Adsorption and oxidation of 1,2-propanediol at a platinum electrode in acid solutions were investigated by cyclic voltammetry and in-situ FTIR spectroscopy. The results demonstrated that 1,2-propanediol oxidized on Pt electrode via a dual path reaction mechanism. 1,2-propanediol may be oxidized into CO_2 through its disso-ciative products on Pt surface. But at lower potentials these dissociative products, which were mainly CO_(ad) and[﹥C=CH_2]_(ad) as detected by in situ-FTIR spectroscopy, may adsorb strongly and accumulate on electrode, empoisoning Pt electrode and suppressing consequently other reactions. However all dissociative products may be oxidized and desorbed from Pt surface when E>0.3 V, which reactivates Pt electrode and enables that 1,2-propanediol oxidizes via reactive intermediates into CO_2. The reactive intermediates were detected by in-situ FTIR spectroscopy under present conditions as OHC—CHOHCH_3 (or CH_2OH—COCH_3) and HOOC—COCH_3 (or HOOC—COCH_3) species.