Controllable Electrochemical Preparation And New Mechanism Of Conductive Polymer Polymelamine

Due to its excellent electrical,optical and magnetic properties,conductive polymers have been the hotspot in the field of material.The electrochemical polymerization method for conductive polymer is deposited directly by monomers which is enriched at the interface between electrode and solution.The thickness,morphology,doping properties and electrical conductivity of conductive polymer can be effectively controlled by adjusting the electrochemical parameters in an appropriate electrolyte.In view of its good stability,abundant nitrogen matrix and amine functional groups,polymelamine(pMel)have been widely applied in sensors,optoelectronic catalysis,color changing devices and battery material as a novel conductive polymer.In this paper,the electrochemical polymerization process of melamine was systematically studied,especially concerning the electropolymerization conditions and mechanism.The main contents were summarized as following:(1)It is ever believed that the strong acid medium is the necessary condition for the preparation of pMel by electrochemical polymerization in recent reports.By separating these two facts in our experiments,here we proved that the presence of Cl~-is the necessary condition in the polymerization process rather than the H~+.We report for the first time the polymerization can take place in acidic,neutral and alkaline solution.The key effects of the acidity of solution,potential window and concentration of Cl~-ions and melamine monomer on the pMel deposition have been further confirmed one by one,respectively.Based on the relevant reactions during the process of electropolymerization,we propose a new mechanism that the deposition of pMel is catalyzed by active chloride.It provides an important basis for the controllable electrochemical polymerization of melamine.(2)We find that the addition of Br~-can also catalyze the electrochemical polymerization of melamine with different pH,which is similar to Cl~-.The polymerization process is very sensitive to trace Br~-in solution and the Br~-can achieve a similar effect of polymerization when its concentration is 100 times lower than Cl~-.The in-situ oxidation of the Br~-makes it more efficient than Cl~-to generate active bromine substance for accelerating the electrochemical oxidation of melamine monomers and the Catalytic deposition of pMel films.However,the catalytic ability of I~-is far less than Cl~-and Br~-.The main reason is that I~-are more easily oxidized into the solid iodine membrane attached to the surface of electrode,which hindering the generation of active halogen species and the continuous polymerization reactions.(3)Based on the above results,the controlled preparation of the polymelamin can be achieve on the glassy carbon electrode,carbon cloth,highly oriented pyrolytic graphite,by the cyclic voltammetry and the constant potential method,respectively;The electrochemically reduced graphene oxide is used as a substrate to obtain pMel/graphene composite film modified electrode,which exhibits high-efficiency electrochemical catalytic oxidation activity for ascorbic acid.Based on this phenomenon,a new electrochemical sensor for ascorbic acid can be established.