The Surface Performances And Electrochemical Behavior Of Layered Transitional Metal Oxides

Layered metal hydroxide (LDHs) is a kind of advanced nanostructured materials.The study of LDHs as a new material for electrochemical modification has receivedmuch attention at home and abroad, because of its inexpensive, simple preparationmethod and controllability of its chemical composition and structure. Recently, theelectrochemical properties of the LDHs have been reported, but the study of therelationship among the surface chemical properties, the microstructure and theelectrochemical properties of LDHs was still a rare. This paper focused on therelationship between the three ones. The charge transport mechanism of the MgFelayered transitional metal hydroxide modified glassy carbon electrode(MgFe-LDH/GCE) was clarified. It provided a theoretical basis for the furtherexploration of layered transition metal hydroxide (MgFe-LDH) and its compositeoxides(MgFe-LDO) as the electrode materials.The electrochemical reaction conditions of the MgFe-LDH/GCE were optimized,the optimal electrochemical reaction conditions in K4[Fe(CN)6] solution was given as:10μL the dosage of modification suspension,5min the pre-concentration time formodifying electrode,0.5mol/L the concentration of electrolyte K4[Fe(CN)6],9.0thepH value of the electrolyte solution.The relationship among electrochemical properties, microstructure and surfacepH was elucidated. The FT-IR bands appeared at1200~1800cm–1region forMg/Fe-LDH samples with different Fe content were conducted by fourier selfdeconvolution and gauss band curve–fitting. Combined with the analysis of SEM、XRD and CO2-TPD test, we found that the higher the crystalline structure, thestronger the surface basicity. The order of surface basicity strengths was as follows:LDH-3> LDH-2> LDH-4. The surface basicity is stronger, electron donating abilitystronger, the active energy of surface reaction lower, and the reaction activity greater.Based on the cyclic voltammetry and AC impedance method, we find thestronger the surface alkaline is, the better oxidation-reduction reversibility andconductivity. The electrochemical response current of LDH-2/GCE、LDH-3/GCE andLDH-4/GCE were in the order of: LDH-3/GCE> LDH-2/GCE> LDH-4/GCE.Among them, the electrochemical response current of LDH-2/GCE was slightlybigger than LDH-4/GCE.We explored the changes of microstructure of modified samples, and clarified thecharge transport mechanism. The SEM, XRD, EDS, FT-IR, TG-DSC and point of zero charge were employed to characterize the change of modified samples from theaspects of the microstructure, thermal stability and the charge properties of particlesurface before cyclic voltammetry scanning reaction and after. The results showedthat K3Fe(CN)6exists in the form of [Fe(CN)6]3–/4–in cyclic voltammetry scanningprocess. after the reaction,[Fe(CN)6]4–adsorbed on the surface of modified samples,forming a coating on the surface of the modified sample, weakening the overallpositive charge strength, leading to its charge density decreased, but layer structure ofsamples has not been destroyed. And interlayer anions is still CO32–,[Fe(CN)6]4–notentering layer of the sample. The charge transformation controled by the diffusionmigration of the [Fe(CN)6]4–in electrolyte. Electron transfer number was1and theelectrontransfer coefficient was0.50901.