Crystalline and amorphous cobalt-based metal oxides for water oxidation reaction – structure, composition, morphology and electrochemical

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dc.contributor.advisorMorin, Sylvie
dc.contributor.authorThekkoot, Sreena Raju
dc.date.accessioned2024-07-18T21:17:12Z
dc.date.available2024-07-18T21:17:12Z
dc.date.copyright2024-02-16
dc.date.issued2024-07-18
dc.date.updated2024-07-18T21:17:11Z
dc.degree.disciplineChemistry
dc.degree.levelDoctoral
dc.degree.namePhD - Doctor of Philosophy
dc.description.abstractCu, Ni, and Fe-substituted cobalt-based amorphous materials (CoOx, CuCo2Ox, Ni0.5Cu0.5Co2Ox, Fe0.1Cu0.9Co2Ox, and Fe0.1Ni0.9Co2Ox) were prepared by thermal decomposition method and employed as electrocatalysts for oxygen evolution reaction (OER). These materials were characterized by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HR-TEM) and X-ray photoelectron spectroscopy (XPS). CuxCo3-xO4 (0 ≤ x ≤ 1), NixCu1-xCo2O4 (0 ≤ x ≤ 0.75) and FeyCux-yCoxO4 (x=1, 1.5 and y = 0.1, 0.15) were also by thermal decomposition method. Surface area measurements were performed using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The catalytic activity of spinel oxides and amorphous metal oxides for OER was analyzed by CV, while kinetic studies were carried out using a rotating disc electrode (RDE). TEM and HR-TEM analysis were performed on polarized and nonpolarized CuCo2O4. The study clearly indicates that the as-prepared CuCo2O4 possesses a higher degree of crystallization compared to the polarized sample. The crystallite size of the samples measured by TEM and XRD analysis is very similar. Surface area measurements indicate that the incorporation of Cu and Ni increased the surface area of amorphous and crystalline samples. The incorporation of Fe increased the surface area of the amorphous samples, while an opposite trend was observed in the case of spinel oxides. XPS analysis indicates that the surface of both amorphous and crystalline samples contains different species and the metal ions exist in different oxidation states. Catalytic activity was measured as a function of geometric and real surface area. Both amorphous and spinel oxides were found to be active for OER. However, when corrected for real surface area, spinel oxides provided much higher current density compared to amorphous samples. Our study indicates that spinel oxides outperform amorphous samples for OER.
dc.identifier.urihttps://hdl.handle.net/10315/42124
dc.languageen
dc.rightsAuthor owns copyright, except where explicitly noted. Please contact the author directly with licensing requests.
dc.subjectChemistry
dc.subjectPhysical chemistry
dc.subjectMaterials Science
dc.subject.keywordsMaterial chemistry
dc.subject.keywordsElectrolysis
dc.subject.keywordsAmorphous
dc.subject.keywordsBinary and ternary spinel oxides
dc.subject.keywordsThermal decomposition method
dc.subject.keywordsElectrocatalysis
dc.subject.keywordsOxygen evolution reaction
dc.subject.keywordsWater electrolysis scanning electron microscopy (SEM)
dc.subject.keywordsEnergy dispersive X-ray spectroscopy (EDX)
dc.subject.keywordsX-ray diffraction (XRD)
dc.subject.keywordsTransmission electron microscopy (TEM)
dc.subject.keywordsHigh-resolution transmission electron microscopy (HR-TEM)
dc.subject.keywordsX-ray photoelectron spectroscopy (XPS)
dc.subject.keywordsElectrochemical impedance spectroscopy (EIS)
dc.subject.keywordsKinetic studies
dc.subject.keywordsRotating disc electrode (RDE)
dc.subject.keywordsFourier Transformed Infrared spectroscopy (FTIR)
dc.subject.keywordsLattice parameter
dc.subject.keywordsCorrelation graphs
dc.subject.keywordsCatalytic activity
dc.subject.keywordsCapacitance
dc.subject.keywordsDouble-layer capacitance
dc.subject.keywordsPseudocapacitance
dc.subject.keywordsCharge transfer resistance
dc.subject.keywordsVolcano plot
dc.subject.keywordsHydrogen evolution reaction
dc.subject.keywordsHydrogen production
dc.subject.keywordsThin films
dc.subject.keywordsCrystal structure
dc.subject.keywordsKoutechy-Levich plots
dc.subject.keywordsTafel plot
dc.subject.keywordsSurface morphology
dc.subject.keywordsCrystallite size
dc.subject.keywordsLattice fringes
dc.subject.keywordsCcrystalline phases
dc.subject.keywordsPolarized and nonpolarized
dc.subject.keywordsDiffraction rings
dc.subject.keywordsBinding energy
dc.subject.keywordsCuxCo3-xO4
dc.subject.keywordsNixCu1-xCo2O4
dc.subject.keywordsFeyCu/Nix-yCo3-xO4
dc.subject.keywordsSurvey spectra
dc.subject.keywordsHigh-resolution spectra
dc.subject.keywordsPeak asymmetry
dc.subject.keywordsShake-up peaks
dc.subject.keywordsSatellite peaks
dc.subject.keywordsFWHM values
dc.subject.keywordsShirley background
dc.subject.keywordsAtomic sensitivity factors
dc.subject.keywordsSpectral fitting parameters
dc.subject.keywordsEquivalent circuit model
dc.subject.keywordsCyclic voltammograms
dc.subject.keywordsRoughness factor
dc.subject.keywordsNyquist plot
dc.subject.keywordsOnset potential
dc.subject.keywordsOver potential
dc.subject.keywordsK-L plot
dc.subject.keywordsMaterials science correlations
dc.titleCrystalline and amorphous cobalt-based metal oxides for water oxidation reaction – structure, composition, morphology and electrochemical
dc.typeElectronic Thesis or Dissertation

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