Harnessing the energy of sunlight to produce fuels is a promising energy-dense route to store solar energy for use at any time. Solar fuels can thus help with the widespread implementation of solar energy which is otherwise limited by its intermittency. Fuels are also a way to condense the diffuse energy of sunlight into a form suitable for demanding portable applications like transportation and aviation. Also known as artificial photosynthesis, solar fuels technology requires high-performance, cost-effective, stable photoactive semiconductors and catalysts in a properly integrated system to efficiently produce fuel. Research at the Conn Center seeks to advance the state-of-the-art in the areas of photoelectrochemistry and electrocatalysis.
Artificial Photosynthesis - incorporating semiconductor photoelectrodes with co-catalysts directly immersed in water for solar-driven electrolysis, has promise as a technology that can produce clean hydrogen fuel more cost-effectively than electrolyzers coupled with photovoltaics.
Catalysts are a critical component in solar fuels to minimize the activation barrier that must be overcome in the electrochemical reactions. Many state-of-the-art electrocatalysts are based on rare noble metals that may not be manufactured cost-effectively for the large-scale energy industry. Replacing these rare materials with earth-abundant elements while maintaining high activity is a challenge.
The increasing concentration of carbon dioxide in the atmosphere is a growing concern for its contribution to climate change. Carbon dioxide can be electrochemically reduced to hydrocarbon and oxygenates, simultaneously producing an energy-dense fuel while helping to mitigate greenhouse gas emissions.
Ammonia is a valuable product which is important for fertilizer production. It is also a liquid near atmospheric pressure, and thus is a promising carbon-free fuel. The direct electrochemical synthesis of ammonia from water and nitrogen is a major challenge because it suffers from strong kinetic competition from hydrogen evolution. Conn Center research in this area is focused on novel approaches to increase the selectivity for ammonia in the electrochemical nitrogen reduction reaction.
The nexus between light absorption, electrochemistry, and product separation in an integrated solar fuels device leads to the possibly of unique system designs which are distinct from either solid-state photovoltaics or isolated electrolyzers. Novel designs are needed to simultaneously get to high efficiency and low cost.