The Electrochemical Behaviors Of Aromatic Derivatives On Hydrophobic Composite Electrodes

As an important branch of organic synthesis, electro-synthesis using clean"electronic" reagent, is fully consistent with requirements of "atom economy" of greenchemistry. Aromatic derivatives are important pharmaceutical material, food additives andchemical raw mateirals and so on. The traditional chemical syntheses of aromaticderivatives usually have a shortage of long reaction steps，low yield，high cost andenvironmental pollution.In this paper，three hydrophobic composite electrodes such as Cu-PTFE, Zn-PTFEand Ni-PTFE were obtained by optimizing the process and were applied to theelectrochemical reduction of benzoic acid, benzaldehyde and electro-oxidation of benzylalcohol, salicylaldehyde, to achieve the electro-synthesis of benzaldehyde, benzyl alcohol,and salicylic acid，respectively. By measuring the electrochemical behaviors of the formerfour kinds of aromatic derivatives on the hydrophobic electrodes, on the basis of thetherory of electric double layer, the models of adsorption and the electrodes reaction ofaromatic derivatives on hydrophobic composite electrodes were established. The mainresults are as follows:（1）Three hydrophobic composite electrodes such as Cu-PTFE, Zn-PTFE andNi-PTFE were fabricated by composite plating method. SEM showed that the compositeelectrodes had an excellent surface morphology, and FT-IR proved the presence of PTFE.Tafel polarization curves showed that composite electrodes had a better stability andcorrosion resistance than that of Cu，Zn and Ni in electro-chemical properties.（2）Using three kind of hydrophobic composite electrodes, the electro-synthesis ofbenzaldehyde, benzyl alcohol and salicylic acid were achieved. Experimental resultsshowed that the yields of the electrochemical reduction of benzoic acid on Cu-PTFE andZn-PTFE hydrophobic composite electrodes were88.4%and79.2%，respectively. Theconversion rate of the electrochemical reduction of benzaldehyde on Ni-PTFEhydrophobic composite electrode was76.4%，the yield of the electrochemical oxidationof benzyl alcohol and the conversion rate of salicylic aldehyde on Cu-PTFE hydrophobiccomposite electrode was83.1%and77.2%，respectively. （3）The electrochemical behaviors of the four aromatic derivatives on hydrophobiccomposite electrodes were determined. The results showed that the electrochemicalreduction of benzoic acid on the composite electrodes maybe had been mainly controlledby electron transfer process. The electrochemical reduction of benzaldehyde and theelectrochemical oxidation of benzyl alcohol and salicylic aldehyde on hydrophobiccomposite electrodes maybe were controlled by electron transfer process and massconcentration diffusion.（4）The models of electrode/solution interface of the four aromatic deirvatives onhydrophobic composite electrodes were established, which presented as four equivalentcircuits, namely R_s[Cc_QR_c(C_dIR_ct]、R_s[C_dlQ(R_ctW)] R_s（C_cQR_c）(C_dI,QR_ct)（QW）and R_s[Cc_QR_c(C_dIR_ct]、...