1. UKM Learning and Research Repository
2. PHD Thesis / Tesis PHD
3. Faculty of Engineering and Built Environment / Fakulti Kejuruteraan dan Alam Bina

Title:	Sputtered tantalum oxide thin film on laser textured and chemically etched silicon wafer for enchanced catalytic activity
Authors:	Norazlynda Samsudin (P77747)
Supervisor:	Nowshad Amin, Prof. Dr.
Keywords:	Universiti Kebangsaan Malaysia -- Dissertations Dissertations, Academic -- Malaysia Thin film Fuel cells Catalysts
Issue Date:	4-May-2021
Description:	Fuel cells are an electrochemical energy converter that converts the chemical energy of fuel into direct current (DC) electricity. The poor rate of catalyst loading at the cathode due to the slow-moving oxygen reduction reaction (ORR) is one of the common problems in polymer electrolyte membrane fuel cells (PEMFC). To overcome the loss of ORR, PEMFC requires the use of a highly active catalyst to promote fuel oxidation at the anode and ORR at the cathode. The aim of this study is two-fold. The first focus is on the implementation of a non-Platinum (Pt) based catalyst due to resource and economic considerations and the second focus is on catalyst structures, more specifically, the pore size and distribution. These two structural factors and the catalyst material affect the interaction between the ionomer and the catalyst particles. Therefore, in order to increase the performance of a PEMFC, the aim is to obtain a membrane-electrode assembly from a non-Pt dependent catalyst structure consisting of a high surface area and porosity. Hence, Ta2O5 has been considered as a potential catalyst in this study. Despite showing low electrochemical activity in earlier studies, Ta2O5 demonstrated the potential to replace Pt. The catalyst structure was laser textured and chemically etched to cause structural modifications to increase the surface area through a grooved and modified surface that also promotes the distribution of the active catalyst. The catalyst structure in this study comprised of Ta2O5 thin film (500-700 nm) sputter deposited on laser textured and chemically etched silicon substrate (600-620 μm). Variation in texturing and etching process parameters resulted in a grooved Si substrate with a pyramid-shaped surface, which was then translated to a Ta2O5 thin film surface deposited over it. Subsequently, a higher-performing Ta2O5 catalyst thin film was achieved from investigating three different deposition temperatures. Post deposition annealing of Ta2O5 thin film at room temperatures of 200 °C and 400 °C were carried out to improve crystallinity and surface morphology. Characterization techniques such as field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), and cyclic voltammetry (CV) were used to investigate the morphological topographical, structural, and electrochemical properties of the samples. The results showed that at a substrate temperature of 400 °C during sputtering, the film had smoother and stronger adhesion to the etched silicon substrates. Ta2O5 particles obtained better crystallinity with orthorhombic phases upon post deposition annealing. Subsequently, several deposition variable investigations resulted in a superior performing Ta2O5 thin film as a catalyst with a pyramid-shaped surface with a laser textured trench of height and width of 225.9 μm and 71 μm, respectively. The best performing Ta2O5 catalyst had layer thicknesses of 700 nm and its catalytic suitability was elucidated by Electrochemical Surface Area (ECSA) of 0.1948 m2/g. The proposed catalyst showed good enhancement for ORR in a prolonged time of continuous potentiostatic electrolysis.,Ph.D.
Pages:	129
Publisher:	UKM, Bangi
Appears in Collections:	Faculty of Engineering and Built Environment / Fakulti Kejuruteraan dan Alam Bina

Items in DSpace are protected by copyright, with all rights reserved, unless otherwise indicated.