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Title:Energy analysis and fabrication of photovoltaic thermal water electrolyzer and ion transport through modified nanoporous membranes
Author(s):Oruc, Muhammed
Director of Research:Nuzzo, Ralph G.
Doctoral Committee Chair(s):Yang, Hong
Doctoral Committee Member(s):Nuzzo, Ralph G.; Kenis, Paul J.A.; Flaherty, David W.
Department / Program:Chemical & Biomolecular Engr
Discipline:Chemical Engineering
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):Hydrogen production
Microfluidic photovoltaic thermal water electrolyzer
Nanoscale ion transport
Abstract:Hydrogen is an environmentally sustainable energy carrier that can be stored. It is not found naturally and therefore must be artificially produced. We can obtain hydrogen from renewable energy, such solar and wind energy, which is environmentally clean. One such a promising options is via electrolysis using electricity from a photovoltaic generator. In the first part of the dissertation we studied a microfluidic energy conversion device to produce hydrogen. Particularly, we proposed a new integrated system – a so-called “photovoltaic thermal water electrolyzer (PVTE)” – which consists of PV cells positioned on top of a planar micro-water electrolyzers in order to harness waste heat as a storable form of energy. The concept of PVTE has the outputs such as electricity and thermal storage, and also it provides hydrogen production efficiently. First, we provided a comprehensive analysis of the overall efficiency of the PVTE system. COMSOL Multiphysics software was used to predict the temperatures for the electrolyte and the PV cells operating at various temperatures and solar fluxes. Moreover, hourly and monthly efficiency analyses were accomplished for Phoenix, AZ in the year 2010. This new integrated approach is advantageous over conventional PV modules (Chapter 2). Second, we fabricated a micro-water electrolyzer which utilizes heat from PV cell and works as a heat sink in order to eliminate additional energy input for electrolysis in order to operate at elevated temperatures. We also presented electrode preparation and fabrication of the electrolyzer. The increase in the hydrogen production rate affirms the predictions of our system that utilizes waste heat from PV (Chapter 3). Finally, we successfully fabricated a new water electrolyzer including hydrophobic porous membrane. This new design allows us to manage gas production and collection in the chamber. By using this method, we are able to collect gases on the top of the electrolyzer at low flow rates at elevated temperatures (Chapter 4). Nanoporous membranes have received great attention in the fields of water desalination, biosensing, and chemical separations. Bare nanopores can be used as size-selective filters but if the surface chemistry of a nanopore is modified by coating it with another substance, however, enhanced separations based other properties can be achieved. Many studies have been performed on ion permselectivity across gold-coated charged surfaces and charged nanopores. In the second part of the dissertation, a focus of interfacial transport phenomena is proposed in order to achieve improved- charge selective nanofluidic systems. There have been numerous studies on the quality of organic SAMs as a blocking mechanism for prevention of ion adsorption. First, we investigated the electrochemical interfacial properties of a well-ordered SAM of 1-undecanethiol (UDT) on evaporated gold surface by EIS in electrolytes without a redox couple. Using a constant phase element (CPE) series resistance model, prolonged incubation times (up to 120 h) show decreasing monolayer capacitance approaching the theoretical value for 1-undecanethiol (Chapter 6). Secondly, we fabricated a membrane permeate flow cell is described with the aim of studying the transport of methyl viologen (paraquat, MV2+) and napathalenedisulfonate disodium salt (NDS2-), using a conductive NCAM. A polycarbonate track etched (PCTE) membrane was made conductive by sputter coating gold on the membrane surface. Transport studies were done in a voltage range in which faradaic current was minimized at the surface of the gold-coated NCAMs. The goal of the transport studies is to demonstrate improved charge selectivity when a well-grown 1-undecanethiol monolayer is assembled at the surface of the NCAM for a wide range of applied potentials (-400 mV < Vappl < 400 mV). Results show the selectivity of charged analytes through the metallized NCAM can be improved by functionalizing the surface with a self-assembled monolayer (SAM). The selectivity coefficients for MV2+ and NDS2- increased with functionalization of undecanethiol on the gold-coated NCAM surface (Chapter 7).
Issue Date:2014-05-30
Rights Information:Copyright 2014 Muhammed E. Oruc
Date Available in IDEALS:2014-05-30
Date Deposited:2014-05

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