The mission of the UNC EFRC Center for Solar Fuels is to conduct research on dye-sensitized photoelectrosynthesis cells, DSPECs, for water splitting and tandem cells for the reduction of carbon dioxide to carbon-based solar fuels. In support of this mission the UNC EFRC established world-class user facilities in Spectroscopy, Device Fabrication & Characterization, Photolysis & Solar Fuels Product Analysis, and Synthesis.
These facilities are directed by UNC EFRC Facilities Director, Dr. Kyle Brennaman, who oversees each capability and takes the lead on the Spectroscopy user facility. He is responsible for building new experimental capabilities, maintaining and calibrating existing instrumentation, and for training and mentoring users. Equipment maintenance, scheduling and training is provided by scientific staff and by UNC EFRC postdoctoral associates.
Each user facility is equipped with a broad array of instrumentation and staffed by one or more Ph.D. staff scientists. We regard the development of a professional technical and support staff to be an essential element of our research infrastructure. In an academic setting, a cadre of professionals offers continuity, expertise, mature capabilities and the ability to work on difficult problems over an extended period, bringing skills typically unavailable in a purely academic environment. The scientific staff positions are professional appointments with considerable oversight authority and support. They are a crucial part of this Center's success because of their ability to foster collaboration and mentor students and postdoctoral fellows. In addition to providing instrumentation and computational support to experimental research teams, staff members implement their own research initiatives, being co-authors on over 110 UNC EFRC papers to date, establish protocols for obtaining high quality, rigorous results, and aid in experiment design, and data interpretation in collaboration with their UNC EFRC colleagues.
Every facility is available to all members of the EFRC, who can work with the staff in a collaborative mode, or become trained for independent use of the instrumentation. The capabilities and staff support provided in the UNC EFRC facilities, combined with those in the Chapel Hill Analytical and Nanofabrication Laboratory, CHANL, provide an extraordinarily powerful support environment enabling rapid progress on difficult, multi-dimensional problems. For example, it is possible for a synthetic chemist to modify an oxide surface with a new assembly, assess interfacial dynamics, characterize surface structure by analysis and imaging, test the assembly within a device configuration, and have theory assistance with data interpretation, all in a matter of days.
A significant challenge for solar energy research is developing a unified picture of the dynamics that occur following light absorption, characterizing the processes that not only lead to fuel production, but also recombination events that limit efficiency. The ability to observe and elucidate photo-induced events on time scales ranging from femtoseconds to seconds, within assemblies, nanostructures, and molecular systems, both in solution and on surfaces requires a broad array of experimental capabilities. The Spectroscopy Facility houses instrumentation for steady-state and time-resolved absorption, emission, and Raman measurements. It supports ancillary efforts in femtosecond Raman spectroscopy, transient grating, visible-pump transient absorption spanning fs-ms time scales, and time-resolved emission microscopy by time-correlated single photon counting.
The Laser Laboratory Director and Facilities Director Dr. Kyle Brennaman has responsibilities that include the design and construction of complex electro-optical instrumentation; serving as research collaborator to the research teams; providing educational and safety training opportunities in the Laser Laboratory including mentoring students; and evolving capabilities to meet the cutting-edge requirements arising from research and analytical needs.
The UNC EFRC Device Fabrication and Characterization Facility is dedicated to materials and device fabrication and has three main functions:
This facility is comprised of two laboratories: the Device Fabrication Laboratory, FABL, and Solar Device Fabrication Laboratory, SDFL.
The Device Fabrication Laboratory, FABL, brings together equipment for materials synthesis and device fabrication/testing. UNC EFRC researchers use the FABL to synthesize nanoparticles by sol-gel methods and to prepare nanoparticle-polymer pastes for thin film deposition by a doctor-blade method or by spin-coating. High surface area conductive nanoparticle thin films are fabricated as substrates for spectroelectrochemical evaluation of molecular water oxidation catalysts and as support structures for performing electrocatalysis. Highly reproducible metal oxide films are fabricated by screen printing and by spray pyrolysis, for dense thin film metal oxide coatings. Key variables controlling batch-to-batch variation are characterized by Brunauer–Emmett–Teller, BET, surface area and pore size analysis, profilometry, TEM, FESEM, and UV-Vis. Quantification of key variables has formed the basis for scale-up and large-scale manufacture of high surface area semiconductor thin films. DSPEC characterization methods include IPCE, current-voltage, and Electrochemical Impedance Spectroscopy EIS. These experiments are complemented by transient photocurrent studies performed in the UNC EFRC spectroscopy facility.
The Solar Device Fabrication Laboratory, SDFL, provides cleanroom, class 1000, research conditions, essential for optimizing electrical performance, reproducibility and reliability of fabricated samples and devices, and houses a stand-alone photovoltaic fabrication/characterization system that includes an array of optical tools under an inert atmosphere. A train of inert atmosphere gloveboxes house a vacuum deposition module, spin-coater, high resolution microscope, and computer-controlled optical goniometer interfaced with a monochromator and solar simulators.
The UNC EFRC leverages equipment in the Chapel Hill Analytical and Nanofabrication Laboratory, CHANL, a multi-department, core user facility at UNC that provides access to a broad array of analytical and nanofabrication instrumentation including EDS-TEM, EDS-SEM, AFM, XPS, UPS, ALD, PLD, and PECVD.
Senior research staff scientist Dr. Seth Marquard provides leadership and support for UNC EFRC efforts in synthesis and characterization of chromophores, catalysts and assemblies and the development of linker technologies. This includes scale-up synthesis of key compounds needed to support ongoing projects in water oxidation, carbon dioxide reduction, polymers, molecular assemblies, and devices.
This synthesis capability has provided a source for common starting reagents, for example functionalized ligands, that are not commercially available, freeing researchers to conduct research without dealing with repetitive and high-volume synthetic protocols.
This facility brings together the equipment necessary to characterize light-driven reactions with an emphasis on solar fuels production. Multiple light-soaking workstations are available. Solar fuels production is monitored using a variety of methods, including O2 sensors, GC and GC/MS. Importantly, we have constructed a capability that allows for real-time, definitive detection of oxygen while monitoring light-driven water splitting reactions in a dye-sensitized photoelectrosynthesis cell by taking advantage of a rotating ring-disk electrode configuration.