硝基苯在离子液体BPyBF4/H2O中的电化学行为

在离子液体1-丁基吡啶四氟硼酸盐(BPyBF₄)的水溶液中,采用循环伏安法(CV)、计时电流法(CA)、恒电位电解及原位红外光谱法(in-situ FTIRS)等研究了硝基苯在铂电极上的电化学还原行为。研究结果表明:硝基苯在离子液体BPyBF₄/H₂O体系中的还原过程是受扩散控制的,其还原产物主要是偶氮苯,经估算得到硝基苯在该体系中的扩散系数为3.1×10^-7 cm²·s^-1,提高温度和加入一定浓度的水均有利于硝基苯在该体系中的电化学还原。

Electrochemical reduction of nitrobenzene in ionic liquid BPyBF4/H2O

The electrochemical reduction behavior of nitrobenzene on platinum electrode was studied with cyclic voltammetry(CV),chronoamperometry(CA),constant-potential electrolysis and in-situ Fourier transform infrared spectroscopy(in-situ FTIRS)in ionic liquid(N-butylpyridinium tetrafluoroborate,BPyBF₄)aqueous solution.The optimum water concentration(15 mol·L^-1)was determined through analyzing the peak current and peak potential of cyclic voltammetry in different ionic liquid solutions. Constant potential electrolysis was performed in a small beaker of 10 ml at the optimum water concentration using platinum foil,graphite and platinum wire as cathode electrode,anode electrode and reference electrode,respectively.Electrolysis products were extracted with ether and determined subsequently by GC-MS and GC.In-situ FTIR spectroscopic experiments were performed on Nicolet 670 FTIR spectrometer equipped with an MCT-A detector cooled with liquid nitrogen.Working electrode was Pt electrode with its surface pressed against the CaF₂ disk window to form a thin layer for IR measurements. Auxiliary electrode was Pt foil and reference electrode was saturated calomel electrode.The reference spectrum was acquired at 0 mV and sample spectra were collected on Pt cathode polarized from -100 mV to -1600 mV at a constant modulation potential(E=-100 mV).The experiment results showed that electrochemical reduction process of nitrobenzene was controlled by diffusion, the main reduction product was azobenzene and the selectivity was about 80%.The diffusion coefficient of nitrobenzene in BPyBF₄-H₂O was 3.1×10^-7 cm²·s^-1,and a suitable temperature and proper amount of water were favorable for the reduction of nitrobenzene.