Physical Chemistry, Inorganic and Materials Chemistry, Solar Energy Conversion
Artificial photosynthesis—creating renewable fuels from sunlight, water, and carbon dioxide in the laboratory—has the potential to transform the way our energy needs are met today. It also raises some fundamental questions in chemistry and materials science. While much characterization has been done, the intermediate states of many useful photo-driven chemical reactions, such as water splitting, remain largely undetermined. Ideally, we would like to apply advanced spectroscopic tools to pinpoint the steps in a mechanistic pathway for fuel generation and then use that knowledge to engineer more efficient systems. The Cuk Lab investigates the machinery of transition metal based light absorbers and catalysts in sunlight to fuel systems with tools that access the microscopic environment of chemically active photo-excited states. In particular, three complimentary spectroscopic tools we use are: 1) transient optical/IR spectroscopy 2) valence band and ambient pressure photoemission and 3) transient x-ray spectroscopy.
The principal challenge of sunlight-to-fuel generation lies in designing a system that completes the two necessary half reactions—the oxidation of water and the reduction of either H+ or carbon dioxide—efficiently in visible, rather than UV, light. In visible light, the overall reaction proceeds closer to the thermodynamic potential of the generated fuel and has limited over-potential. The system, then, needs to exploit the time scale, molecular configuration, and electronic potential of electron transfers between the light absorber, catalyst, and reactants to generate fuel efficiently. This leads to constraints both on the individual components and the overall architecture of the artificial photosynthetic system. For example, in all current proposals for visible light driven fuel formation, much like in a plant, the light absorber and catalyst are two, spatially separated components. One reason for this is that the initial charge separation step has to isolate electrons and holes long enough for chemical reactivity to take place. Several other design principles are currently being pursued, and more are yet to be discovered.
B.S.E. Princeton University (2000); Ph. D. Stanford University (2007); NSF Predoctoral Fellow; Miller Postdoctoral Fellowship, UC Berkeley (2007-2010); Faculty Scientist, Chemical Sciences Division, Lawrence Berkeley National Laboratory (2010-present); Young Investigator Research Award, Airforce Office of Scientific Research (AFOSR) (2012-2015)