Abstract: The electroreduction of nitrobenzene in room temperature ionic liquidEMimBF₄ on Pt electrode was investigated. The experimental results from cyclic voltammetry and constant-potential electrolysis show that the mechanism of the reaction was two molecules and three steps electrochemical process with eight-electrons transferred: anion radical arose in the first step; two-electrons were transferred in the second step and accompanied with coupling reaction of radicals and protonation and dehydrate, the main product was azoxybenzene; two-electrons were transferred in the third step, and azobenzene was achieved. The stronge interaction between EMimBF₄ and nitrobenzene, and its intermediates yielded in the process of electroreduction caused the selective reaction. By controlling the reduction potential, the electroreduction of nitrobenzene to azoxybenzene and azobenzene had a high selectivity and high conversion. The concentrations of nitrobenzene and water in EMimBF₄ have great effect on the electrochemical behavior. With the increasing of nitrobenzene concentration, the electroreduction peak potential of cyclic voltammogram around -1.47 V was shifted to negative value, and the current density was increased, as well as the water had reversed effect on the electroreduction peak potential, and increased current density.

Key words: Nitrobenzene, EMimBF₄, Electroreduction, Green chemistry, Selectivity