As one of the most abundant and widespread energy resources available, sunlight is very attractive as a renewable energy source that could be the pillar of a sustainable energy future. In the last several decades, decreasing costs of photovoltaic technology have helped spur the spread of solar electricity. However, at present solar energy remains a minor player in the global energy landscape. Even if a revolution in the manufacture of photovoltaics successfully reduces the cost of solar electricity to a level that is economically competitive with fossil fuels, the widespread implementation of solar as a primary energy source will require the ability to overcome the intermittency of sunlight.
In order to have energy from the sun at night, a cost-effective storage mechanism is needed. Battery systems are generally too expensive for large scale deployment, and mechanical storage methods, such as pumping water uphill, require enormous reservoirs in favorable locations. An ideal solution would be to store solar energy in the form of chemical bonds – to convert sunlight into energy-dense fuels. Nature utilizes this approach through the mechanism of photosynthesis. However, the energy conversion and storage efficiency of even the most rapidly growing plant is less than 0.5%. By pursuing artificial photosynthesis, the combination of light absorbing semiconductors and highly active catalysts in an inorganic photoelectrolysis system, cost-effective fuel production at higher efficiency is possible.
The Conn Center is striving to develop new and promising approaches in the field of solar fuels. This effort includes the study of novel photoactive semiconductors and surface preparations to make efficient photoelectrodes for fully integrated solar water-splitting systems. The center is also researching the design of electrolyzers to reduce carbon dioxide into useful hydrocarbon fuels efficiently and with high yield. New photovoltaic technologies specifically designed to drive a desirable electrolysis reaction are under investigation as well. Each of these research thrusts is dedicated to lowering the ultimate cost of solar fuels production.
Near Term Objectives
Hydrogen – Establish the viability of ambient humidity based solar hydrogen generation and move towards commercial implementation.
Carbon Neutral Liquid Fuels – Improve the selectivity for the electrocatalytic synthesis of liquid hydrocarbons and liquid ammonia.
Earth-abundant Catalysis – Characterize a new acid-stable water oxidation catalyst with high activity but low noble metal content, and develop a high-throughput plasma synthesis reactor for the combinatorial synthesis of phase-pure catalyst particles.
Photoelectrochemistry - Research and establish characterization capabilities for small, light-driven photoelectrodes running CO2 reduction.
Mid Term Objectives
Hydrogen – Incorporate high-efficiency photoactive components with Conn Center derived catalysts and reactor designs for stable solar hydrogen generation and collection.
Carbon Neutral Liquid Fuels – Use the strategies of cascade reactor design, plasma-based reactants, and/or nanostructured catalysts to produce desired liquid fuels in high yield with high energy conversion efficiency.
Earth-abundant Catalysis - Build a library of plasma-synthesized catalyst data based on composition, and use the results in coordination with theory and informatics groups to predict new compositions of promising catalysts.
Photoelectrochemistry – Leverage photoelectrodes to improve the selectivity of producing liquid hydrocarbon and/or ammonia products.
Long Term Objectives
Hydrogen – Develop an integrated solar fuels system to meet the DOE target of 25% solar-to-hydrogen efficiency using cost-effective materials.
Carbon Neutral Liquid Fuels – Achieve solar-driven liquid hydrocarbon synthesis at 5x the efficiency of plants, and synthesize liquid ammonia from air and water at comparable efficiency.
Earth-abundant Catalysis – Demonstrate acid-stable water-splitting without noble metals at efficiencies comparable to the current state-of-the-art.
Photoelectrochemistry – Develop particle-based PEC systems for stable water-splitting at an efficiency that is promising for commercialization.
Joshua Spurgeon, PhD
Theme Leader for Photovoltaics/Solar Fuels
Conn Center for Renewable Energy Research
University of Louisville
Ernst Hall Room 101, 216 Eastern Parkway
Louisville, KY 40292
Email Dr. Spurgeon