- Ph.D., University of California, Santa Barbara
Research Interests
Jaramillo Lab General Research Focus
Recent years have seen unprecedented motivation for the emergence of new energy technologies. Global dependence on fossil fuels, however, will persist until alternate technologies can compete economically. We must develop means to produce energy (or energy carriers) from renewable sources and then convert them to work as efficiently and cleanly as possible. Catalysis is energy conversion, and the Jaramillo laboratory focuses on fundamental catalytic processes occurring on solid-state surfaces in both the production and consumption of energy. Chemical-to-electrical and electrical-to-chemical energy conversion are at the core of our research. Nanoparticles, metals, alloys, sulfides, nitrides, carbides, phosphides, oxides, and biomimetic organo-metallic complexes comprise our toolkit of materials that can help change the energy landscape. Tailoring catalyst surfaces to fit the chemistry is our primary challenge.
Fuel Cells
A fuel cell is a promising energy conversion device in which chemical energy is directly converted to electrical energy, for example: H2 + 1/2O2 → H2O, DG = -1.23 eV. Despite the attractiveness of fuel cell technologies, a number of materials-related problems have hindered their wide-spread use. Projects in this area are geared for the development of promising new electrocatalytic materials by studying fundamental electrochemical surface phenomena, with the ultimate aim of overcoming the technological challenges in fuel cell catalysis. In the case of Proton Exchange Membrane (PEM) fuel cells, the greatest challenge is the cathode, where much of the cell voltage must be "consumed" in order to drive the sluggish reaction kinetics of the Oxygen Reduction Reaction (ORR), O2 + 4H+ + 4e- → 2H2O. The potential at which the cathode operates is also problematic, as unwanted surface chemistry is often induced, including surface oxidation, poisoning by OH- adsorption, or electrochemical dissolution. New materials are needed as the best catalysts for this reaction are based on Pt or Pt-group metals which are scarce and expensive. Similar problems exist at the anode; earth-abundant and catalytically active materials are needed for the oxidation of fuels such as hydrogen and methanol with the constraint that they must also be tolerant to possible catalyst poisons such as carbon monoxide or CHx species, which are ubiquitous in fuel feeds, or could even exist as reaction intermediates.
Electrocatalysis for Energy Production
In contrast to fuel cells, electrolysis consumes electrical energy in order to produce fuel, for example: H2O → H2 + 1/2O2, DG = +1.23 eV. This particular case of water-splitting has gained substantial attention as of late as extremely high-purity hydrogen is produced. There is a need for new materials that drive the kinetics of both half-reactions - the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) - in order to minimize electrolysis operating voltage. Despite decades of research, both half-reactions are still poorly understood.
CO2 electro-reduction to fuels such as methane, methanol, or formic acid is another reaction of technological importance. If renewable energy is coupled to the reduction of CO2 to C1 fuels, near net-zero CO2 emission could be achieved. Plus, producing a liquid fuel has obvious advantages to H2 as storage and transportation are not problematic. Nevertheless, the surface chemistry of CO2 reduction is difficult as large energy barriers are present compared to proton reduction to H2, a process which generally competes for surface sites.
Photoelectrochemical Energy Conversion
Solar energy is the ultimate form of renewable energy, as the sun deposits 4 orders of magnitude more energy on the earth’s surface than we consume. Photovoltaics coupled to water electrolyzers are one means of solar-derived fuel, however at present, capital costs for both systems prevent this scheme from becoming reality on a large scale. A similar, but more direct approach is to combine both technologies into one photo-electrochemical device: a solar-photon absorbing semiconductor (or combination of semiconductors) whose surfaces are optimized for water reduction and/or oxidation. In this project, new materials and architectures will be investigated with the aim of developing systems with appropriate semiconductor properties for light absorption, electron-hole energies, and charge transport, with surface properties tailored for stability and electrocatalytic activity.
Research projects:
1. Nanoparticulate catalysts for fuel cell cathodes.
2. Poison tolerant catalyst surfaces for fuel cell anodes.
3. Water electrolysis and reversible fuel cells.
4. CO2 electro-reduction chemistry.
5. New materials for semiconductor photoelectrochemistry.
Recent Publications
(1) T.F. Jaramillo, J. Zhang, B. L. Ooi, E. Fernández, S. Saadi, J. Bonde, J. Ulstrup, J.K. Nørskov, I. Chorkendorff, Hydrogen evolution on supported [Mo3S4]4+ cubane clusters (in preparation, 2007).
(2) T.F. Jaramillo, S. Jayaraman, E.W. McFarland, Bimetallic Au-Pt nanoparticles for the electro-oxidation of methanol (in preparation, 2007).
(3) G. S. Karlberg, T.F. Jaramillo, E. Skúlason, J. Rossmeisl, T.
Bligaard, J.K. Nørskov, Cyclic voltammograms for H on Pt(111) and Pt(100) from first principles Phys. Rev. Lett., 2007, 99, Art. No. 126101.
(4) T.F. Jaramillo, K. P. Jørgensen, J. Bonde, J. H. Nielsen, S. Horch,
I. Chorkendorff, Identifying the active site: Atomic-scale imaging and ambient reactivity of MoS2 nanocatalysts Science, 2007, 317, 100.
(5) J. Greeley, T.F. Jaramillo, J. Bonde, I. Chorkendorff, J.K. Nørskov, Computational high-throughput screening of electrocatalytic materials for hydrogen evolution Nature Materials, 2006, 11, 909.
(6) S. Jayaraman, T.F. Jaramillo, S.-H. Baeck, E.W. McFarland, Synthesis and characterization of Pt-WO3 films as methanol oxidation catalysts for low-temperature polymer electrolyte membrane fuel cells J. Phys. Chem. B, 2005, 109, 22958.
(7) T.F. Jaramillo, S.-H. Baeck, A. Kleiman-Shwarsctein, K.-S. Choi, G.D. Stucky, E.W. McFarland, Automated electrochemical synthesis and photoelectrochemical characterization of Zn1-xCoxO thin films for solar hydrogen production J. Comb. Chem., 2005, 7, 264.
(8) T.F. Jaramillo, S.-H. Baeck, A. Kleiman-Shwarsctein, and E.W. McFarland, Combinatorial electrochemical synthesis and screening of mesoporous ZnO for photocatalysis Macromol. Rapid Comm., 2004, 25, 297.
(9) S.-H. Baeck, K.-S. Choi, T.F. Jaramillo, G.D. Stucky, and E.W. McFarland, Enhancement of photocatalytic and electrochromic properties of electrochemically fabricated mesoporous WO3 thin films Adv. Mater., 2003, 15, 1269.
(10) B. Roldan-Cuenya, S.-H. Baeck, T.F. Jaramillo, E.W. McFarland, Size and support dependent electronic and catalytic properties of Au0/Au3+ nanoparticles synthesized from block co-polymer micelles, J. Am. Chem. Soc., 2003, 125, 12928.
(11) T.F. Jaramillo, S.-H. Baeck, B. Roldan-Cuenya, E.W. McFarland, Catalytic activity of supported Au nanoparticles deposited from block copolymer micelles J. Am. Chem. Soc., 2003, 125, 7148.
(12) W. Siripala, A. Ivanovskaya, T.F. Jaramillo, S.-H. Baeck, E.W. McFarland, A Cu2O/TiO2 heterojunction thin film cathode for photoelectrocatalysis Sol. Energ. Mat. Sol. C., 2003, 77, 229.
(13) S.-H. Baeck, T.F. Jaramillo, G.D. Stucky, E. McFarland, Controlled electrodeposition of nanoparticulate tungsten oxide Nano. Lett., 2002, 2, 831.
(14) T.F. Jaramillo, A. Ivanovskaya, E.W. McFarland, High-throughput screening system for catalytic hydrogen-producing materials J. Comb. Chem., 2002, 4, 17.
Ph.D. Students Supervised – Undergraduate Institution
