Elizabeth J. Podlaha-Murphy
Albert Sacco Jr., Richard Kurtz
Date of Award
Master of Science
Department or Academic Unit
College of Engineering. Department of Chemical Engineering.
Chemical engineering, Electrosynthesis
Optoelectronic devices, Hydrogen as fuel, Titanium dioxide films, Water - Electrolysis, Nanoparticles
Biochemical and Biomolecular Engineering | Electronic Devices and Semiconductor Manufacturing | Power and Energy
Hydrogen is one alternative clean fuel for micro-scale devices when generated by solar irradiation through water splitting. The photoelectrolysis of water has been intensively studied since the seminal work of Fujishima and Honda in 1972 where titania was used as an anode photocatalyst . While TiO2 is an attractive material because it is inexpensive and a well known catalyst for water dissociation, one of the major drawbacks that limits its practicality is that it only absorbs light in the UV region. Recent results of combining Au nanoparticles with TiO2 has been suggested to prevent electron hole recombination of the photoexcited titania hence enhancing its photoelectrochemical performance [2-3]. In this study, three layers of TiO2 is electrosynthesized on ITO substrates using the generation of base method followed by annealing steps in between each deposited layer and a final heat treatment to ensure the anatase crystallinity of the deposits. . The thickness of the films was between 2-3 µm with a cracked morphology. Au nanoparticles were subsequently electrodeposited onto the electrogenerated TiO2 and pulsing conditions that affect the Au nanoparticle size and uniformity were investigated. Pulsed waveforms included a nucleation, growth and dissolution step. Results indicate that the first nucleation step is key in determining the size of the particles and the clumps formed as well as their density. Photoelectrochemical tests including step photoresponse analysis under different light sources, electrochemical impedance analysis and intensity modulated photocurrent spectroscopy techniques were employed to characterize the enhanced photoelectrochemical response of three different forms of the TiO2-Au composite: (1) TiO2 decorated with Au nanoparticles, TiO2/Au, (2) TiO2 with embedded Au nanoparticles in a sandwich fashion, TiO2/Au/TiO2, and (3) TiO2 with embedded and decorated Au nanoparticles, TiO2/Au/TiO2/Au. Results indicated that electrodeposited gold on titania resulted in the highest photocurrent response under UV irradiation (25 µA, 14 µA/cm2) and a red-shifting of the photoresponse of the composite. The second best photoresponse was obtained with the TiO2/Au/TiO2/Au samples (17 µA, 9 µA/cm2), and the third best response compared to pristine titania was generated with the TiO2/Au/TiO2 sandwiched samples (11 µA, 6 µA/cm2). Aging of the samples and additional photoelectrochemical tests resulted in a decreased in the photocurrent response.
Elhajj, Jessy, "Electrosynthesis of TiO2-Au composites for water splitting applications and their photoelectrochemical characterization" (2008). Chemical Engineering Master's Theses. Paper 4. http://hdl.handle.net/2047/d10018542
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