3. Electronic Theses and Dissertations (ETDs) - All submissions
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Item MXene-based nanostructures for electrochemical CO oxidation(2024) Hussien, Belal Salah Mohammed2-D MXene based nanostructure owns several unique physicochemical and catalytic properties. Herein, this research used MXene (Ti3C2Tx) for the electrochemical COoxid reaction experimentally for the first time. This work divided to two sections, the first is using mono metal decorated Ti3C2Tx and the second using binary metals decorated Ti3C2Tx to investigate and compered the electrochemical COoxid reaction activity of mono and binary metals with Ti3C2Tx. At first, Ti3C2Tx (TX=OH, O, and F) well-ordered and highly exfoliated 2-D nanosheets used as substrate for the NPs growth and prepared via the selective chemical etching and delamination of MAX phase (Ti3AlC2) with sonication assistance to form Ti3C2Tx nanosheets. After that, Mono and binary metals were prepared via using a facile method by in situ impregnation of Pd or Pt or both salts with Ti3C2Tx in aqueous medium under sonication without using reducing agent or surfactant. The as prepared Pt/Ti3AlC2, Pd/Ti3AlC2, and PtPd/Ti3AlC2 composition and structure were characterized by the scanning electron microscope (SEM), Energy Dispersive X-Ray Analyzer (EDX), the transmission electron microscope (TEM) equipped with high-angle annular dark-field scanning transmission electron microscopy (HAADF-SEM), energy dispersive spectrometer (EDS), The X-ray photoelectron spectroscopy (XPS) spectra and The X-ray diffraction patterns (XRD). The electrochemical COoxid activity were explored using The cyclic voltammogram (CVs), linear sweep voltammogram (LSV), chronoamperometry (CA) and electrochemical impedance spectroscopy (EIS) for all prepared of different samples using Gamry electrochemical analyzer using a three-electrode system contains a Pt wire (counter electrode), Ag/AgCl (reference electrode), and glassy carbon ((3mm) WE) in an aqueous solution saturated with CO of three electrolytes acidic (0.1 M HClO4), neutral (0.5 M NaHCO3) and basic (0.1M KOH) at different sweep rate. The first study showed the electrochemical activity and effect of mono metals NPs of Pd/Ti3C2Tx compared with metal-free Ti3C2Tx in acidic electrolyte, Interestingly, Ti3C2Tx displayed poorer COoxid activity and the integrating of Pd NPs enhance the activity, ascribed to the combination between outstanding physical and chemical properties of Ti3C2Tx and the catalytic advantages of Pd. In contrast, the second study the electrochemical COoxid activity for binary compared with mono NPs decorated Ti3C2Tx. Results showed PdPt/ Ti3C2Tx was substantially superior to Pd/ Ti3C2Tx, Pt/ Ti3C2Tx, and metal-free Ti3C2Tx in three electrolytes experimentally, owing to the electronic and synergetic effect of PdPt and physiochemical properties of Ti3C2Tx. This study may pave the way for the employment of Ti3C2Tx in electrochemical CItem Electrocatalytic detection of drugs of abuse using onion-like carbon based electrocatalysts(2024) Ehirim, Tobechukwu JusticeSubstance abuse is a serious problem worldwide. Among abused substances, tramadol and alcohol are one of many. There is an urgent need to use electrochemical method for their detection since electrochemistry methods are simple, low-cost, high sensitivity and can easily be miniaturised. This PhD work reports the first investigation on the application of nanodiamond-derived onion-like carbons (OLC) and conductive carbon black (CB) as (i) electrocatalysts for the detection of tramadol, and (ii) as support materials for nano-sized palladium electrocatalysts (Pd/OLC, Pd/CB, Pd-CeO2/OLC) for the detection of ethanol. The catalysts were characterised with X-ray diffraction (XRD), Raman, Brunauer– Emmett–Teller (BET), Thermal gravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS), Scanning electron microscopy (SEM) and Transmission electron microscopy (TEM). For the detection of tramadol, OLC gave the best sensing performance compared to CB. Theoretical calculations (DFT simulations) predict that OLC is better because it allows for weaker interaction energy with tramadol (Ead = -26.656 eV) than CB (Ead = -40.174 eV). OLC-modified glassy carbon electrode (GCE-OLC) shows a wide linear calibration curve (55 – 392 M), high sensitivity (0.0315 A /M), low limit of detection (LoD) and quantification (LoQ) of 3.8 and 12.7 M, respectively. OLCmodified screen-printed electrode (SPE-OLC) successfully detected tramadol in real tramadol drug and human serum. The OLC-based electrochemical sensor promises to be useful for sensitive and accurate detection of tramadol in clinics, quality control and routine quantification of tramadol in pharmaceutical formulations. For the oxidation and detection of ethanol, Pd/CB, Pd/OLC and Pd-CeO2/OLC, were studied as catalysts. In comparison, adding ceria (CeO2) to Pd/OLC, the performance was enhanced significantly than in carbon-only support for palladium. GCE/PdCeO2/OLC shows the best electrocatalytic performance (i.e., high current density, fast electron transport, etc). DFT calculation, supported by XPS and HRTEM data, predict that this high activity may be related to CeO2 modulating the electronic properties of the catalyst. GCE/Pd-CeO2/OLC gave wide linear range for ethanol sensing (38.5 – 286 mM), excellent sensitivity (0.00024 mA mM-1 ) and LoD of ~ 8.7 mM. The GCE/Pd-CeO2/OLC shows excellent potential for application in real samples of commercial alcoholic beverages and human serum, with satisfactory recoveries (89 – 108 %).