Nanostructured Metal Oxide Coatings for Electrochemical Energy Conversion and Storage Electrodes

The realization of an energy future based on safe, clean, sustainable, and economically viable technologies is one of the grand challenges facing modern society. Electrochemical energy technologies underpin the potential success of this effort to divert energy sources away from fossil fuels, whether one considers alternative energy conversion strategies through photoelectrochemical (PEC) production of chemical fuels or fuel cells run with sustainable hydrogen, or energy storage strategies, such as in batteries and supercapacitors. This dissertation builds on recent advances in nanomaterials design, synthesis, and characterization to develop novel electrodes that can electrochemically convert and store energy.

Chapter 2 of this dissertation focuses on refining the properties of TiO2-based PEC water-splitting photoanodes used for the direct electrochemical conversion of solar energy into hydrogen fuel. The approach utilized atomic layer deposition (ALD); a growth process uniquely suited for the conformal and uniform deposition of thin films with angstrom-level thickness precision. ALD’s thickness control enabled a better understanding of how the effects of nitrogen doping via NH3 annealing treatments, used to reduce TiO2’s bandgap, can have a strong dependence on TiO2’s thickness and crystalline quality. In addition, it was found that some of the negative effects on the PEC performance typically associated with N-doped TiO2 could be mitigated if the NH3-annealing was directly preceded by an air-annealing step, especially for ultrathin (i.e., < 10 nm) TiO2 films. ALD was also used to conformally coat an ultraporous conductive fluorine-doped tin oxide nanoparticle (nanoFTO) scaffold with an ultrathin layer of TiO2. The integration of these ultrathin films and the oxide nanoparticles resulted in a heteronanostructure design with excellent PEC water oxidation photocurrents (0.7 mA/cm2 at 0 V vs. Ag/AgCl) and charge transfer efficiency.

In Chapter 3, two innovative nanoarchitectures were engineered in order to enhance the pseudocapacitive energy storage of next generation supercapacitor electrodes. The morphology and quantity of MnO2 electrodeposits was controlled by adjusting the density of graphene foliates on a novel graphenated carbon nanotube (g-CNT) scaffold. This control enabled the nanocomposite supercapacitor electrode to reach a capacitance of 640 F/g, under MnO2 specific mass loading conditions (2.3 mg/cm2) that are higher than previously reported. In the second engineered nanoarchitecture, the electrochemical energy storage properties of a transparent electrode based on a network of solution-processed Cu/Ni cores/shell nanowires (NWs) were activated by electrochemically converting the Ni metal shell into Ni(OH)2. Furthermore, an adjustment of the molar percentage of Ni plated onto the Cu NWs was found to result in a tradeoff between capacitance, transmittance, and stability of the resulting nickel hydroxide-based electrode. The nominal area capacitance and power performance results obtained for this Cu/Ni(OH)2 transparent electrode demonstrates that it has significant potential as a hybrid supercapacitor electrode for integration into cutting edge flexible and transparent electronic devices.

Beyond the Convent Walls: The Local and Japan-wide Activities of Daihongan’s Nuns in the Early Modern Period (c. 1550–1868)

This dissertation examines the social and financial activities of Buddhist nuns to demonstrate how and why they deployed Buddhist doctrines, rituals, legends, and material culture to interact with society outside the convent. By examining the activities of the nuns of the Daihongan convent (one of the two administrative heads of the popular pilgrimage temple, Zenkōji) in Japan’s early modern period (roughly 1550 to 1868) as documented in the convent’s rich archival sources, I shed further light on the oft-overlooked political and financial activities of nuns, illustrate how Buddhist institutions interacted with the laity, provide further nuance to the discussion of how Buddhist women navigated patriarchal sectarian and secular hierarchies, and, within the field of Japanese history, give voice to women who were active outside of the household unit around which early modern Japanese society was organized.

Zenkōji temple, surrounded by the mountains of Nagano, has been one of Japan’s most popular pilgrimage sites since the medieval period. The abbesses of Daihongan, one Zenkōji’s main sub-temples, traveled widely to maintain connections with elite and common laypeople, participated in frequent country-wide displays of Zenkōji’s icon, and oversaw the creation of branch temples in Edo (now Tokyo), Osaka, Echigo (now Niigata), and Shinano (now Nagano). The abbesses of Daihongan were one of only a few women to hold the imperially sanctioned title of eminent person (shōnin 上人) and to wear purple robes. While this means that this Pure Land convent was in some ways not representative of all convents in early modern Japan, Daihongan’s position is particularly instructive because the existence of nuns and monks in a single temple complex allows us to see in detail how monastics of both genders interacted in close quarters.

This work draws heavily from the convent’s archival materials, which I used as a guide in framing my dissertation chapters. In the Introduction I discuss previous works on women in Buddhism. In Chapter 1, I briefly discuss the convent’s history and its place within the Zenkōji temple complex. In Chapter 2, I examine the convent’s regular economic bases and its expenditures. In Chapter 3, I highlight Daihongan’s branch temples and discuss the ways that they acted as nodes in a network connecting people in various areas to Daihongan and Zenkōji, thus demonstrating how a rural religious center extended its sphere of influence in urban settings. In Chapter 4, I discuss the nuns’ travels throughout the country to generate new and maintain old connections with the imperial court in Kyoto, confraternities in Osaka, influential women in the shogun’s castle, and commoners in Edo. In Chapter 5, I examine the convent’s reliance upon irregular means of income such as patronage, temple lotteries, loans, and displays of treasures, and how these were needed to balance irregular expenditures such as travel and the maintenance or reconstruction of temple buildings. Throughout the dissertation I describe Daihongan’s inner social structure comprised of abbesses, nuns, and administrators, and its local emplacement within Zenkōji and Zenkōji’s temple lands.

Exploring these themes sheds light on the lives of Japanese Buddhist nuns in this period. While the tensions between freedom and agency on the one hand and obligations to patrons, subordination to monks, or gender- and status-based restrictions on the other are important, and I discuss them in my work, my primary focus is on the nuns’ activities and lives. Doing so demonstrates that nuns were central figures in ever-changing economic and social networks as they made and maintained connections with the outside world through Buddhist practices and through precedents set centuries before. This research contributes to our understanding of nuns in Japan’s early modern period and will participate in and shape debates on the roles of women in patriarchal religious hierarchies.