Research On The Capacitance Performance Of Transition Metal Oxide Nanoparticles

The transition metal oxides from a series of elements in the d region of theperiodic table, Because of the unpaired electron in the virtual orbital, it has thedifferent physical and chemical properties with other elements. The transition metaloxides have been attracted widely attention due to its prominent function.The transition metal oxides have the similar extranuclear strucure with noblemetal oxides, so they have the similar pseudocapacitive performance, and the specificcapacitance of transition metal oxides is1¹00times of carbon electrode material,therefore the transition metal oxides are a kind of very promising Electrochemicalcapacitor materials. Excepting the outstanding pseudocapacitive performance,transition metal oxides can be also compounded with metal oxide matrix, and then itwould have a great effect on the morphology of composite electrode, nucleationgrowth as well as activity. Because the transition metal oxide is widely used in variousfields, more and more researchers are committed to the preparation and properties oftransition metal oxide nanomaterials. In this thesis, the author have successlysynthesized nano-Co₃O₄, nano-Mn₃O₄, nano-WO₃, nano-SnO₂, nano-CuO andnano-NiO particles. And also have analyzed its’ composition, structure, surfacemorphology and capacitance performance. Fainlly we have discussed the effect ofdoped nano-Co₃O₄and nano-Mn₃O₄on PbO₂composite electrode in composition,structure, surface morphology and capacitance performance. Research results are asfollows: （1） Physical characterization of several kinds of transition metal oxidenanoparticles.Through the modern physical test （XRD, SEM） for physical characterization:nano-Mn₃O₄is tetragonal phase, particle size is about40⁶0nm, uniformdistribution and good dispersibility; By changing the surfactant to prepare nano-Co₃O₄, the nano-Co₃O₄is spinel structure, particle size are6¹0nm cube, in whichsurfactant sodium oleate is more advantageous to the nano-Co₃O₄particlesdispersion; By using different surfactant to prepare nano-WO₃, the nano-WO₃is200nm x200nm x10nm nano films, in which sodium dodecyl sulfate is moreadvantageous to the nano-WO₃particles dispersion; Nano-SnO₂is rutile phase,particle size is about5⁸nm; By changing the adding manner of NH4CO₃to preparethe nano-CuO, the nano-CuO were respectively well-proportioned spherical in180²00nm and180nm x175nm spindle; Nano-NiO is about50⁶0nm, the uniformdistribution and good dispersion.（2） Analysis of electrochemical propeties of several transition metal oxidesElectrochemical tests were performed using electrochemical workstation. Thespecific capacitance of nano-Mn₃O₄is206F/g, the specific capacitance of nano-SnO₂is102F/g. In this article we analyze the capacitance performance of severaltransition metal oxide materials from the nuclear outer electronic structure of activeelements: the number of nuclear outer electron is less, the more likely lose electons,occur oxidation-reduction reaction and generate pseudocapacitance, so the specificcapacitance of nano-Mn₃O₄is much bigger.（3） The effect of doped nano-Co₃O₄and nano-Mn₃O₄on PbO₂compositeelectrodeThe effect of doped transition metal oxides on PbO₂composite electrode instructure, surface morphology and capacitance performance has been enhancedgreatly. Compared with pure PbO₂electrode, the grain size of composite electrodebecomes from a few microns to tens of nanometers; to form the three-dimensionalporous structure; the effective area of electrode is also increased. The specificcapacitance of nano-PbO₂+Mn₃O₄and nano-PbO₂+Co₃O₄were215F/g and338F/g respectively, compared with the pure PbO₂, the pseudocapacitive performance hasbeen greatly improved.