Scientific Grand Challenge

Energy will be the Next Scientific Grand Challenge.

The past two decades have witnessed a dramatic increase in global energy consumption. While this need has been largely met by fossil fuels, the rapidly increasing global competition for this limited resource and the expectation that the Earth’s energy needs will double by 2050 and triple by the end of the century, has generated growing concern over future availability.

Combine the above with the mounting evidence that carbon dioxide emissions are adversely affecting global climate, and it becomes increasingly clear that developing renewable carbon-neutral energy sources constitutes a grand challenge for the scientific community.

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Creating Tomorrow's Solar Fuels Today

The ultimate solution to the world’s need for renewable, environmentally-friendly energy is all around us. The sun provides about 10,000 times our current daily energy needs, but it will always be limited until two significant challenges are met. In the U.S. alone, a 10% solar efficient device would require a collection area of approximately 1.6×1011 square meters, roughly the land area of North Carolina, to meet the country's current energy needs. Equally daunting is the fact that the sun goes down at night.

To be practical, utilization of solar energy requires energy storage on massive scales, far greater than any available based on existing technology. Natural photosynthesis provides an inspiration and biomass a partial solution, but not for meeting the vast power density requirements of urban centers or industrial complexes. Useful working devices will require much higher efficiencies, lower cost, and simplicity of design and maintenance.

Artificial Photosynthesis

The only practical approach at the required scale is "Artificial Photosynthesis" with "solar fuels" as the product. Solar fuels are high-energy molecules like carbohydrates or hydrogen with the energy of the sun stored in chemical bonds. Target reactions are water splitting into hydrogen and oxygen and light-driven reduction of CO2 to CO or other reduced forms of carbon.

The UNC Energy Frontier Research Center - EFRC

Thomas MeyerTo address the challenges in creating a sustainable energy future, the UNC EFRC: Center for Solar Fuels, funded by the US Department of Energy, Office of Basic Energy Sciences, was established in 2009 at one of the top five public research universities in the United States, the University of North Carolina at Chapel Hill. Led by a distinguished faculty, including members of the National Academy of Sciences, UNC EFRC leverages key discoveries made at UNC during the past 20 years and collaborations with other research institutions to assemble a critical mass of scientists working together on energy-related research. The research center is headquartered at UNC-CH in partnership with the University of Texas at San Antonio, Georgia Institute of Technology and Brookhaven National Laboratory.

The UNC EFRC is conducting research on capturing sunlight to drive solar fuel reactions. The Center's efforts range from basic research on fundamental processes to integrating components into sub-systems and sub-systems into prototypical devices. The research utilizes a broad, multidisciplinary approach in a highly collaborative setting drawing on expertise across a broad range of disciplines in chemistry, physics, and materials sciences. The primary target is a Dye Sensitized Photoelectrosynthesis Cells (DSPEC) for solar fuels production as illustrated below.


Solar Fuels

Several platforms are under investigation but the primary focus is on Dye Sensitized Photoelectrosynthesis Cells (DSPEC). This approach utilizes molecules and molecular assemblies for catalysis in photoelectrochemical configurations closely related to those used in Dye Sensitized Solar Cells (DSSC). In contrast to a DSSC, where the target is creating a photopotential and photocurrent, the target of a DSPEC is production of a high energy fuel with oxygen as the co-product in the physically separated compartments of a photoelectrochemical cell. The UNC EFRC approach is distinctive based on the design and utilization of separate functional modules, maximizing their performance, and integrating them into device prototypes featuring both single and tandem photoelectrode configurations.

Multiple themes have been developed in parallel — light absorption, excited state electron and energy transfer, electron and proton transfer driven by free energy gradients, and catalysis of water oxidation and water/CO2 reduction — with integration in photoelectrochemical cell configurations. In the modular approach the separate components are designed and tested for maximum performance and then integrated into the final DSPEC architecture. DSPEC research benefits from, and is enriched by, parallel research in electrocatalysis and Dye Sensitized Solar Cells.

Hallmarks of Center research are: (1) Interfacial and solution reaction mechanisms for water oxidation and CO2 reduction; (2) Design and synthesis of molecular chromophore-catalyst assemblies which combine light absorption, electron transfer, and catalysis; (3) Preparation, characterization, and stabilization of derivatized photoelectrocatalytic interfaces; (4) Application of theory and experiment to establish guiding principles for component design, integrated systems, and devices; (5) Development and characterization of nano-structured oxide materials, (6) Integration of components into device prototypes and device evaluation; (7) Augmentation of research findings and multidisciplinary strengths in research collaborations and research extensions with national laboratories, other EFRCs, and industry, extending the research findings of the EFRC through the translation stage to device prototypes.