关键词: 硝基苯, 离子液体, 电还原, 原位红外

Abstract: 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.

Key words: nitrobenzene, ionic liquid, electro-reduction, in-situ Fourier transform infrared spectroscopy