Date on Master's Thesis/Doctoral Dissertation

8-2020

Document Type

Doctoral Dissertation

Degree Name

Ph. D.

Department

Mechanical Engineering

Degree Program

Mechanical Engineering, PhD

Committee Chair

Park, Sam

Committee Member

Berfield, Thomas

Committee Member

Wang, Hui

Committee Member

Sunkara, Mahendra

Committee Member

Sumanasekera, Gamini

Author's Keywords

flow battery; boron doped diamond; energy storage; corrosion; solvent window; oxygen evolution

Abstract

As the interest and implementation of renewable energy accelerates, so does that of grid energy storage. It is widely believed that a cost-effective energy storage technology will bring about the proliferation of renewable energy. Redox flow battery (RFB) technology represents a promising solution to cost-effective grid energy storage. Compared to other technologies, RFBs have a long lifetime, high efficiency, are non-flammable, significantly reduce cost, and separately scale power and energy. The separation of power and energy enables increased energy capacity by simply adding electrolyte volume. Of the challenges facing RFB technology, one readily apparent is the cost of the active species in the all-vanadium RFB, the most commercialized of the RFB iterations. One route aimed at answering this challenge is the examination of a wide range of low-cost active species. The aim of this dissertation is to extend that search through the utilization of an electrode material not previously considered for RFBs. This dissertation will examine the utilization of boron doped diamond (BDD) as an alternative electrode in aqueous RFBs with the potential for a longer lifetime, higher efficiency, and lower cost active species compared to traditional RFB electrodes. The benefits of BDD include high conductivity, low capacitive currents, inertness, fouling and corrosion resistance, and high overpotential to gas evolution. The growth of BDD using microwave plasma-assisted chemical vapor deposition is investigated using different growth recipes and substrates. Characterization includes scanning electron microscopy (SEM), energy-dispersive x-ray spectroscopy (EDX), Raman spectroscopy, and Fourier-transform infrared spectroscopy (FTIR). The viability of various redox chemistries is examined using electrochemical methods including charge/discharge cycling, cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). It is found that Ce3+/Ce4+ and Mn2+/Mn3+ are promising redox couples on a BDD electrode. Based on peak-to-peak separations of 254.8 mV for cerium and 140 mV for Mn, low overpotentials are evident. High reversibility and long lifetimes are apparent based on peak current ratios nearing unity and cycling data exceeding 300 cycles with improved peak current densities. In addition, the ability to scale up BDD was shown via growth on various materials including porous graphite and quartz fibers.

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