Hybrid Systems for Sustainable Chemistry.
Natural photosynthesis serves as an inspiration for the development of sustainable fuel producing systems. We create such functional systems by integrating enzyme and synthetic catalysts in nanostructured, often photoactive materials. Our approach from synthetic and materials to biological chemistry is highly cross-disciplinary.
currently collaborates with the following laboratories:
Department of Chemistry, Cambridge: Dominic S. Wright
Cavendish Laboratory, Cambridge: Richard H. Friend, Ullrich Steiner & Sumeet Mahajan
Medical Research Council, Mitochondrial Biology Unit, Cambridge: Judy Hirst
Imperial College London, UK: James R. Durrant & A. William Rutherford
University of York, UK: Robin Perutz
University of East Anglia, UK: Julea Butt
University of Leeds, UK: Lars Jeuken
Universite Joseph Fourier, Grenoble, France: Juan C. Fontecilla-Camps
World Premier Institute, Advanced Institute for Materials Research, Japan: T. Adschiri & N. Asao
Strenghts of Synthesis, Chemical Biology and Materials.
Synthesis. We synthesize and exploit physical and chemical catalysts in our hybrid systems. The former allows us to harvest light in the form of a dye and the latter catalyses the formation of an energy-rich compound, a fuel. We are particularly interested in bio-inspired catalysts for proton and carbon dioxide reduction.
Chemical Biology. Nature provides us with highly efficient and selective enzymes, which contain inexpensive transition metals in their catalytic active site. We are interested in understanding how these enzymes work, and applying these principles to design biomimetic catalysts and photochemical systems. We also use enzymes such as hydrogenases (proton to H2 conversion), photosystem II (water to O2) and formate dehydrogenase (CO2 to formic acid) directly as catalysts in biotechnologically relevant devices.
Materials. Our synthetic and biological redox catalysts will ultimately end up on an electrode, where they will be interrogated by different electrochemical and photoelectrochemical techniques. This approach allows us to study their intrinsic catalytic properties and how the catalyst modification improves the electro- or photocatalytic perfomance of the solid-state material. We are currently particularly interested in catalysts integrated in nanostructured semiconductor electrodes._______________________________________________
Below please find a short summary of our latest projects:
fuel generation with molecular
catalysts on dye-sensitized TiO2.
Here, we build up on the reasonably well understood principles of dye-sensitised TiO2 (as used in dye-sensitised solar cells) and incorporate 3d transition metal catalysts to evolve H2 from water (instead of producing electricity). Solar-light driven H2 production was achieved by co-attaching a cobaloxime H2 evolution catalyst and a ruthenium photosensitiser to a TiO2 nanoparticle in an aqueous sacrificial electron donor buffer medium. The solar H2 evolution system operates under visible light irradiation at pH 7 and room temperature. We study the electron transfer rates in this colloidal systems in collaboration with the group of James Durrant at Imperial College London.
References: Lakadamyali, F.; Reynal, A.; Kato, M.; Durrant, J. R.; Reisner, E. Chem. Eur. J 2012, 18, 15464–15475; Lakadamyali, F.; Reisner, E. Chem. Commun. 2011, 47, 1695–1697.
Photoelectrochemical water oxidation with nature's water oxidizer photosystem II.
In this project, we immobilize photosystem II on electrode surfaces and study its photocatalytic activity with different techniques. The project addresses basic questions about the effect of an exogenous substrate on the electron transfer kinetics in photosystem II and the activity of the resulting hybrid electrodes serves as an inspiration and benchmark for related synthetic systems. We showed recently that photosystem II can be integrated in a transparent and mesoporous indium-tin oxide electrode. We observed direct electron transfer from photosystem II to the electrode via the natural QB and an unnatural QA electron transfer pathway. This project is executed in collaboration with the group of Bill Rutherford at Imperial College London and kinetic investigations are in progress with Richard Friend's group at Cambridge.
Reference: Kato, M.; Cardona, T.; Rutherford, A. W.; Reisner, E. J. Am. Chem. Soc., 2012, 134, 8332-8335.
Oxygen-tolerant synthetic catalysts for fuel generation.
An obvious requirement for water splitting is the need for an H2 evolution catalyst that operates in the presence of O2. However, there has been little progress in the development of homogeneous catalysts that operate under significant O2 levels. Efficient catalysts such as the noble metal platinum and hydrogenases suffer from cross-selectivity for O2 reduction and typically high O2 sensitivity, respectively. Here, we address this challenge and study the catalytic activity of homogeneous catalysts in the presence of O2. We recently found that a water soluble cobaloxime catalyst not only operates in pH neutral water and at room temperature, but also in the presence of atmospheric O2.
Reference: Lakadamyali, F.; Kato, M.; Muresan, N.M.; Reisner, E. Angew. Chem. Int. Ed., 2012, 51, 9381–9384.
Polyoxometallate nanocages as single source materials for electro- and photocatalysis.
We recently started work to investigate heterobimetallic polyoxotitanates as precursors for the deposition of stoichiometrically-controlled doped TiO2 films. We found that Co-doped TiO2 cages (TiCo) are excellent precursors for the preparation of CoOx water oxidation electrocatalyst with a novel conducting metal oxide architecture. The TiCo cages are a reservoir for cobalt ions in a titania matrix on fluoride-doped tin oxide electrodes and form in situ the active CoOx catalyst for O2 evolution in an aqueous pH neutral phosphate buffer. This project is executed in collaboration with the group of Dom Wright at Cambridge.
References: Lai, Y.-H.; Lin, C.-Y.; Lv, Y.; King, T.C.; Steiner, A.; Muresan, N. M.; Gan, L.; Wright, D. S.; Reisner, E. Chem. Commun., 2013, 49, 4331-4333; Lv, Y.; Willkomm, J.; Steiner, A.; Gan, L.; Reisner, E.; Wright, D.S. Chem. Sci., 2012, 3, 2470-2473.
Electrocatalytic H2 evolution with molecular catalysts on nanostructured electrode.
The low overpotential electrolysis of water with inexpensive and efficient materials allows for the affordable conversion of electricity into the fuel H2. To achieve this goal, we have developed a high-yield multi-step synthesis of a robust cobaloxime H2 evolution catalyst that can be integrated in a nanostructured indium-tin oxide (ITO) environment. The novel backbone of the Co catalyst allows for site-specific immobilization on the nanostructured ITO surface with excellent stability via phosphonic acid anchors. The hybrid electrode showed high current densities, and spectroelectrochemical studies and extensive surface characterization demonstrate that the immobilized molecular catalyst remained intact on the electrode when applying a low potential.
Reference: Muresan, N. M.; Willkomm, J.; Mersch, D.; Vaynzof, Y.; Reisner, E. Angew. Chem. Int. Ed., 2012, 51, 12749-12753.
for electro- and photocatalytic fuel generation.
Solar fuel generation, in particular the development of inexpensive and efficient photoelectrochemical (PEC) cells for sunlight-driven water splitting is of considerable current interest. We have developed a PEC system that consists of a novel p-type Cu2O/NiOx nanocomposite photocathode coupled to an n-type WO3 nanosheet photoanode. The complementary band gap of Cu2O (2 eV) and WO3 (2.6 eV) permits for complementary light absorption and solar water splitting without external bias. We demonstrated that a Cu2O-based electrode for H2 evolution can be prepared free of noble metals and we show its utilisation in a PEC water splitting cell made solely from earth abundant elements.
Lin, C.-Y.; Lai, Y.-H.; Mersch, D.; Reisner, E. Chem.
Sci., 2012, 3,
|Information about more ongoing projects will become available soon.|
and Physical Sciences Research Council (EP/H00338X/2
for postgraduate studies:
- Marshall/EPA scholarship (MPhil
scholarship for Christina Chang)
Society for the Promotion of Science (for Masaru Kato)
Science Council of Taiwan (for Chia-Yu Lin)
- Marie Curie fellowship from European Union (for Jenny Zhang)
- Isaac Newton Trust
(Trinity College, Cambridge) & German Research
Foundation (for Moritz Kuehnel)