Studies On Electrochemical Dehalogenation Mechanism Of Halo-benzoic Acid By In Situ FTIR Spectroscopy

Electrochemical dehalogenation of halobenzoic acid has been studied widely for its social benefit and economic returns.In this paper,in situ FTIR and cyclic.voltammetry are used to investigate electrochemical dehalogenation reactive characteristics and reaction mechanism of halobenzoic acid from the molecular level for its theoretic guide to the industrial application.Firstly,3-clorobenzoic acid and 2,4-dichlorobenzoic acid had been chosen as model molecules to investigate electrochemical dehalogenation mechanism using in situ FTIR and cyclic voltammetry.The experimental results showed that Pd/Ti electrode exhibited a higher electrochemical activity for the reduction process of 3-CBA and 2,4-DCBA in NaOH solution comparing with Cu,Ag and Ti electrodes.The reason is that Ti has good conductivity,stability,and Pd is good at storing up hydrogen,which reacted with 3-CBA molecule adsorbed on the Ti electrode surface.In situ FTIR results showed that the electrochemical dechlorination of 3-CBA and 2,4-DCBA were the process of dechlorination and hydrogenation.3-CBA was electroreduced to its free radical ion after receiving an electron.Then the 3-CBA free radical took off a chloride ion and produced the benzoic acid free radical.After receiving another electron and a proton,the final product benzoic acid was obtained.The 2,4-DCBA took off two chloride ions and receiving two electrons to produce the final product benzoic acid because of its two chloride ions.In order to study the influence of substituting group to dehalogenation reactions,the electrochemical dehalogenation sequence was researched by in situ FTIR and cyclic voltammetry.It showed that the dehalogenation activity sequence on Cu?Ag and Pd/Ti electrodes is 2-CBA<2-BBA<2-IBA.Particularly,2-BBA showed the fastest speed once the reaction was occured on Pd/Ti electrode.The polar of bond and polarizability determined the difficulty level of the bone breaking.The two factors determined relative activity of the three halobenzoic acids,and the results was:C-I>C-Br>C-Cl.The influence of cathode substrate to electrochemical dehalogenation reaction was studied using cyclic voltammetry and in situ FTIR with 3-CBA as the model molecule in this paper.among the palladized electrodes,Pd/C,Pd/Pt,Pd/GC,Pd/Ti,the Pd/Pd electrode exhibited a low electrochemical activity for the reduction process of 3-CBA,and the others could react with 3-CBA in different degrees.The cathode substrate was found to have important effect on the performance of the electrochemical dehalogenation.The different performance might due to the stability and adsorbability of the cathode substrate.For the hydrogen which stored by Pd reacted continuously with 3-CBA adsorbed on the cathode substrate surface.The Pd nanoparticle load on Ti took on globular and that scattered on GC.The ladger surface area maintained higher dehalogenation activity than other Palladized electrodes.Pd/Ti and Pd/GC electrode showed the alluring prospect electrode material on electrochemical dehalogenation area.