Supercapacitive Research And Electrocatalytic Analysis Based On Ruthenium Or Manganese Oxide And Porous Au Or Pt Modified Electrodes

The supercapacitors are a kind of new energy-storing devices of high current density,high power density,multicycling tolerance,as well as environment benign and maintenance-free or low-maintenance nature,which have shown high development potential in relevant fields.The ruthenium dioxde supercapacitor is an important and typical supercapacitor,however,the wide use of which is somewhat limited by the high price of ruthenium and the controversial mechanism of its supercapacitance reaction.Two-dimensional graphene and one-dimensional carbon nanotubes exhibit unique properties of good conductivity,high structural strength,high surface area,and so on.The use of them to load ruthenium for developing supercapacitors can improve the supercapacitive performance including the material-utilization efficiency and mass specific capacitance.Electrocatalysis refers mainly to a catalysis action in which the charge transfer reaction at the electrode|electrolyte solution interface is accelerated.Porous Pt or Au is a good electrocatalytic material for some small organic molecules,which can thus be employed in the fields of fuel cell and analysis/testing.In this dissertation,we have briefly reviewed the recent progress of supercapacitor,noble metal and carbon nanomaterial.The electrochemical reactions of ruthenium are studied in detail by electrochemical quartz crystal mierobalance(EQCM),and the mechanisms of ruthenium electrochemical reactions and capacitance reaction of RuO2 are discussed.Graphene and carbon nanotube loaded ruthenium materials for supercapacitor applications are investigated.Porous Pt and porous Au are prepared for electrocatalysis and analysis.Oxygen-evolution anodic electrodeposition is exploited for preparation of MnO2 supercapacitor.The main contents are as follows.1.A ruthenium dioxide modified electrode was prepared by cathodic electrodeposition of ruthenium followed by anodic oxidation treatment.EQCM,scanning electron microscopy(SEM),X-ray diffractometry(XRD)and X-ray photoelectron spectroscopy(XPS)are used to study the electrochemistry of electrodeposited ruthenium and the supercapacitive reaction of electrosynthesized ruthenium dioxide.The supercapacitive reaction of hydrous ruthenium dioxide,being both a proton conductor and an electron conductor,is suggested from the experimental data to be hydrogen underpotential deposition process and electrical double-layer effect inside the hydrous ruthenium dioxide structure in different potential ranges,rather than a process related to ruthenium-valence change.2.A ruthenium dioxide-carboxylated graphene(CG)composite was prepared by composite electrodeposition for supercapacitive study.Ruthenium and CG were coelectrodeposited at-0.25 V vs SCE on a quartz crystal microbalance(QCM)Au electrode in a stirred aqueous dispersion containing 0.6 mM RuCl3,1 mg mL-1 CG and 0.1 M H2SO4.The Ru-CG composite was electrooxidized by cyclic voltammetry in 0.5 M aqueous H2SO4 to yield a RuO2-CG/QCM electrode for supercapacitor research.In situ QCM technique and ex situ SEM,XPS,XRD spectroscopy,and Raman spectroscopy were used for process monitoring and/or film characterizations.The RuO2-CG/QCM electrode exhibited an apparent specific capacitance of 756 F g-1,an energy density of 101 Wh kg-1 at a power density of 2.5 kW kg-1,it is larger than literature reported.This method may be extended to preparation of other supercapacitace materials.3.Ruthenium and end-opening mutiwalled carbon nanotubes(MWCNTs)were coelectrodeposited in a stirred dispersion of 0.6 mM RuCl3,1 mg mL-1 MWCNTs and 0.1 M H2SO4,followed by cyclic voltammetry anodic oxidation in 0.5 M H2SO4 to yield a RuO2-MWCNTs.The RuO2-MWCNTs was anodically dissolved RuO2 on the outer walls of MWCNTs and partially retain RuO2 filled in the MWCNTs,yielding the RuO2(in)-MWCNTs.QCM technique and SEM,XPS,XRD and Raman spectroscopy were used for process monitoring and/or film characterizations.The RuO2(in)-MWCNTs/QCM electrode exhibited a high specific capacitance of 556 g-1 and a high energy densities of 77.5 Wh kg-1 at a power density of 2.5 kW kg-1,and its potential-cycling life is larger than 500 000 cycles.4.A bimetallic Pt-Ru composite was coelectrodeposited in H2PtCl6,RuCl3 and H2SO4 solution,and its anodic treatment to remove ruthenium in H2SO4 solution(ruthenium oxides can be dissolved at sufficiently high potentials)yielded a porous Pt modified electrode.Such porous Pt shows good electrocatalytic activity toward methanol oxidation,giving a current density of catalyzed methanol oxidation of 213 mA cm-2 and a higher running stability than either electrodeposited Pt or electrodeposited Pt-Ru composite.In addition,after adding an Au salt into the electrodeposition bath,a bimetallic porous Pt-Au composite was similarly prepared,which shows good electrocatalytic activity toward oxidation of formic acid and methanol.5.An Au-Ru composite was coelectrodeposited in HAuCl4,RuCl3 and H2SO4 solution,and its anodic treatment to remove ruthenium in H2SO4 solution yielded a porous Au modified electrode..The porous Au shows good electrocatalytic activity toward glucose oxidation for high-performance nonenzymatic amperometric detection of glucose in neutral medium,with limit of detection(LOD)of 0.1 mM and a linear detection range from 0.4 mM to 7.4 mM.6.Porous MnO2 was anodically electrodeposited in aqueous surfuric acid containing manganese acetate at oxygen evolution potential,as charactered by QCM,SEM,XPS and Raman spectroscopy The specific capacitance of porous MnO2 reached 198 F g-1,the energy density was 34.4 Wh kg-1 at 400 W kg-1 power density,and the stability was good.