Development of novel synthesis routes, architectures, and catalyst modifications toward the improvement of multicomponent photoelectrodes for solar energy conversion

Jason Andrew Seabold, Purdue University

Abstract

Throughout history humans have taken advantage of the energy stored in the bonds of chemical fuels in order to survive. However, within the past few centuries an immense trove of energy has been realized in the form of fossil fuels, sparking a global revolution which changed how energy is used and distributed and shaped our modern industrial society. Unfortunately, current worldwide energy demand continues to grow in the face of a dwindling fossil fuel supply and controversy over global climate change caused by runaway atmospheric CO2 levels. This untenable situation requires a radical approach to energy generation and storage. A new source of energy is desperately needed. This source must exist in near limitless supply, and its storage and subsequent use must avoid the production of harmful CO2. The Sun produces a colossal 3.8x1026 J of energy per hour. Of that massive output, the relatively few photons (3x10−8 percent) that manage to strike the earth each hour carry enough energy to power the planet for an entire year. Harvesting this energy and storing it cheaply and efficiently is one of the "holy grails" of modern scientific endeavor. Although it is a very recent human aspiration, some of earth's organisms have been using this boundless resource for ages, harvesting light and storing its energy in one of its most compact forms, the chemical bond, through the process of photosynthesis. Scientists are racing to understand and mimic this process. To accomplish this task, they must construct systems which can efficiently absorb light, drive electrons to perform complex and demanding chemical reactions, and then effectively store the products for consumption in an overall process that must be cheap and reliable. This work focuses on the development of materials and material hybrid pairs which can absorb visible light and shuttle the subsequently produced energetic electrons either to an external load, or to locations where they can converting their potential energy into chemical energy in the form of H2 fuel via water hydrolysis. The early chapters focus on water splitting, and include experiments on various photoanodes and a photocathode. The final chapter details the development of a photovoltaic photoelectrochemical cell, which generates electrical power instead of a chemical fuel. The following chapters can also be categorized into two major themes. The first theme is the construction of efficient multicomponent photoelectrodes for solar energy conversion. Chapter 2 (WO3/Co-Pi OEC), Chapter 3 (BiVO4/FeOOH) and Chapter 6 (CdTe/TiO2), fall within this category. These composite electrodes are able to accomplish what neither component can achieve alone. The second theme is the synthesis and study of relatively unexplored multinary metal oxides and metal phosphates which absorb visible light and can be effectively utilized to harvest solar energy. Relevant chapters include Chapter 3 (BiVO4/FeOOH), Chapter 4 (Ag3PO 4 and Ag4V2O7), and Chapter 5 (CuBi 2O4).

Degree

Ph.D.

Advisors

Choi, Purdue University.

Subject Area

Alternative Energy|Inorganic chemistry|Materials science

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