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Highly efficient solar H2 production by photo-biocatalytic water splitting

English title Highly efficient solar H2 production by photo-biocatalytic water splitting
Applicant Lippert Thomas
Number 180181
Funding scheme Bilateral programmes
Research institution Paul Scherrer Institut
Institution of higher education Paul Scherrer Institute - PSI
Main discipline Material Sciences
Start/End 01.10.2018 - 30.09.2021
Approved amount 248'918.00
Resource not found: 'b32db384-870a-464e-9bca-736634c1190f'

Keywords (5)

artificial photosynthesis ; solar water splitting ; inorganic-biological hybrid; hydrogen generation ; photobiocatalysis

Lay Summary (Italian)

Lead
Il sole e' una fonte di energia virtualmente illimitata. Uno dei compiti principali che la comunita' scientifica sta affrontando e' cercare di utilizzare l'energia solare in modo efficiente e pulito per l'ambiente. Le celle fotovoltaiche rendono l'energia solare immediatamente disponibile come energia elettrica e le batterie permettono di immagazzinare l'energia. In un approccio diverso invece, l'energia del sole puo' essere convertita nell'energia chimica di un combustibile, l'idrogeno prodotto dalla scissione della molecola d’acqua. Questo progetto di ricerca intende studiare un modo innovativo per rendere il piu' possibile efficiente questo processo in modo da ottenere un combustibile rinnovabile, pulito e sempre disponibile dove e quando e' necessario.
Lay summary
Nell'approccio piu' tradizionale la scissione della molecola d'acqua avviene utilizzando un semiconduttore che e' in grado di assorbire la luce del sole e rendere disponili cariche elettriche le quali possono poi essere utilizzate per generare ossigeno e idrogeno.
Questi ultimi due processi elettrochimici avvengono in corrispondenza di opportuni materiali detti co-catalizzatori. 
Nel complesso, si tratta di un processo foto-elettro-catalitico molto complicato che puo' funzionare grazie all'utilizzo di diversi materiali ottimizzandone la composizione e il reciproco accoppiamento. 
Uno dei passaggi piu' delicati e' sicuramente l'utilizzo delle cariche elettriche generate nel semiconduttore da parte dei catalizzatori. Sotto questo aspetto, la natura fornisce un esempio molto interessante di utilizzo di coppie ossido-riduttive per la produzione di idrogeno: gli enizimi idrogenasi. Queste molecole biologiche purificate sono state utilizzate per produrre artificialmente idrogeno accoppiate con semiconduttori inorganici come TiO2. Raramente questi enzimi sono stati utilizzati non purificati, ovvero usando l'intera cella del batterio che li produce. In tal caso il vantaggio sta nei ridotti costi di produzione e nella maggiore stabilita' chimico-fisica della cultura. Mai prima pero' le cellule batteriche che producono un enzima idrogenase sono state accoppiate con semiconduttori inorganici composti da ossonitruri. Al contrario del TiO2 comunemente usato, questi materiali possono assorbire la gran parte dello spettro di luce visibile che riceviamo dal sole, mentre i semiconduttori comunemente usati fino ad ora possono assorbire solo le energie piu' alte, verso l'ultravioletto. 
L'accoppiamento di una cellula batterica modificata per produrre l'enzima idrogenase richiesto con un semiconduttore in grado di assorbire la luce solare nello spettro visibile e' la novita' di questo progetto di ricerca che in caso di successo potrebbe rivelare le linee guida per la fabbricazione di un dispositivo ibrido biologico-inorganico in grado di produrre idrogeno dall'acqua a costi molto bassi. 
Il progetto trae forza da un incontro pressocche' perfetto delle rispettive competenze dei gruppi di ricerca svizzero e giapponese. In Svizzera i semiconduttori responsivi alla luce visibile verranno realizzati mentre in Giappone verranno condotti i test con le culture batteriche modificate in grado di esprimere l'enzima desiderato. Il progetto prevede uno scambio continuo di campioni, know-how e ricercatori tra i due paesi per tutta la durata del lavoro di ricerca. 
Direct link to Lay Summary Last update: 24.09.2018

Responsible applicant and co-applicants

Name Resource not found: '84cc0509-a3de-4a74-af63-b053822e3e56'

Gesuchsteller/innen Ausland

Employees

Collaboration

Group / person Country
Types of collaboration
Imperial College London, Department of Materials, Prof. J. A. Kilner Great Britain and Northern Ireland (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
- Research Infrastructure
Laboratory for Micro and Nanotechnology, Paul Sherrer Institute, Prof. L. Heyderman Switzerland (Europe)
- Publication
- Research Infrastructure
Institut für Materialphysik, Universität Göttingen, Dr. Vladimir Roddatis Germany (Europe)
- Publication
- Research Infrastructure
Kyushu University, Prof. Tatsumi Ishihara Japan (Asia)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
ETH Zurich, High Energy Physics, Dr. M. Döbeli Switzerland (Europe)
- Publication
- Research Infrastructure
Electrochemistry Laboratory, Paul Scherrer Institute, Prof. T. J. Schmidt Switzerland (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication

Associated projects

Number Title Start Funding scheme
172708 Laser interaction with materials for thin film deposition: From fundamentals to functional films 01.08.2017 Project funding (Div. I-III)

Abstract

The increase in the global population, the fast economic development of highly populated counties and the presence of large areas of poverty worldwide demand for ever growing available energy to feed, sustain and spread the inalienable rights for better life style and services to more and more people. The current energy economy, based on fossil fuels, has demonstrated its inherent limitations from geo-political and environmental point of views. Nuclear power plants can also not be considered as environmentally sustainable power sources due to the very high costs and to the still unsolved problem to store the nuclear waste safely. Not to forget the tragic consequences of nuclear disasters.The urgent demand for the reduction of greenhouse gases on a global scale makes the development of a radically new approach to energy production and usage a matter not deferrable any longer. Earth, in less than a century has received from human activityies damages so severe to put at risk not only the biodiversity of the planet but also the survival of mankind itself. Nature offers a virtually unlimited source of energy in form of heat and light, i.e. the sun. The direct conversion of solar power into electric power has attracted enormous research and engineering efforts and unprecedented steps forward to increase conversion efficiency and reliability have been made over the last decades. However, the development of an efficient direct conversion technology would not be sufficient since sun light is not necessarily immediately available when and where electricity is needed. An even more important scientific and technological challenge is the conversion of sun light into storable energy - as for example accumulated electric charge in a rechargeable battery - or storable energy carrier in form of a fuel. The latter approach typically targets the generation of hydrogen gas by using solar energy to split the water molecule. Hydrogen gas can then be used to feed a fuel cell to produce electric power with high efficiency and with a low or even no environmental impact since when hydrogen and oxygen (from air) are used as fuel, water is the only by-product of the reaction. The renewable and sustainable production of hydrogen can be achieved using photovoltaic cells to sustain the electrolysis of water. Alternatively, sun light can be directly used to photo-generate the charge carriers needed for the oxidation and reduction of water thus allowing the storage of chemical energy in form of hydrogen gas. The latter approach is also called artificial photosynthesis as it is directly inspired from what plants and green algae do when they use sun light to oxidize water molecules releasing oxygen and protons (that can be used for hydrogen production) and converting CO2 into biochemical energy, e.g. in the form of complex hydrocarbons as reducing agents, glucose, and other biomolecules. In a photosynthesis process that meets human needs the photoelectrochemical process would be simpler since just hydrogen (or methanol) would have to be generated. The involved processes are: •Harvest efficiently visible light and generate electrons and holes with energies suitable to drive the oxygen reduction and hydrogen evolution reactions •Separate the photo-generated charge carries making them available for the electrochemical process •Ensure efficient charge transport between the different electrochemically active sites and catalyze the water splitting process •Development of an artificial leaf as a suitable supporting structure or scaffold to arrange all components •Ensure the physicochemical stability of the whole system Through millions of years of evolution nature found the way to make all the above steps working but to mimic this extraordinarily complex process with an artificial system turns out to be a formidable task and an enormous scientific and technological challenge. Artificial photocatalytic systems are based on a triad assembly where the light absorber and sensitizer element are electrochemically linked in tandem to the water oxidation and the hydrogen evolution catalysts. Several approaches, from all-inorganic to all-biological system designs, have been investigated over the last decades and of course all of them offer peculiar strengths and weaknesses. In natural photosynthesis over half of the efficiency is used to separate excited charges. An optimistic sunlight-biomass efficiency is in the range of a few percent. On the other hand, inorganic photovoltaic systems easily reach 20% conversion of sunlight into electricity suggesting that high solar-to-fuel efficiency should also be possible. However, while inorganic photovoltaics have made tremendous progress, catalysis specificity has not. If clean solar fuel is to be realized as a feasible technology, the application must also be simple and work in a variety of environments - i.e. fuel from waste water. From this perspective, biological photosynthesis might be inefficient, but biological systems are champions at producing specific products in large quantities in complex and even “dirty” cellular environments. Inorganic - biological hybrid systems represent a potential approach to achieve photobiocatalytic water splitting combining the high efficiency of inorganic photovoltaic with the low cost and catalytic specificity of biological systems. In such hybrid systems the photoactive material is an inorganic semiconductor where the photo-generated charge carriers are separated and extracted. Instead, the hydrogen catalyst is an enzyme of the hydrogenase family. When combined to an electron donor/acceptor (cofactor) these enzymes catalyze the reversible oxidation of H2 to protons, thus releasing hydrogen and re-oxidizing the cofactor. One typical approach to design and fabricate inorganic-biological hybrid photocatalysts relies on the combination of (dye-sensitized) TiO2 with a purified bacterial hydrogenase. The proposed research plan aims at giving a contribution in this field by investigating the potential of an innovative coupling between a visible light-sensitive inorganic semiconductor (instead of the mainly UV-sensitive TiO2) and a whole bacterial cell (instead of a purified enzyme). The Japanese Group of Prof. Ishihara has recently reported the first direct application of an inorganic semiconductor/whole-cell photobiocatalytic reaction for the production of hydrogen. TiO2 was used as the inorganic semiconductor and a recombinant strain of Escherichia coli was applied instead of purified enzymes. Compared to purified enzymes this approach offer easier manipulation, better stability and lower costs, and compared to other relevant microorganisms E. coli has a significantly higher growth rate. The Swiss Group of Prof. Lippert has consolidated expertise on oxynitride semiconductors. Some of these materials have bad gap widths and energy positions of the band edges almost ideal for an application in solar water splitting. The widely used TiO2 can in fact efficiently utilize only about 4% of the solar spectrum. Oxynitride semiconductors instead promise a much more efficient solar light utilization. Moreover, a unique method was developed to grow oxynitride thin films with different crystalline and crystallographic properties. These are excellent model systems to investigate several interfacial subtle mechanisms that often represent the most important rate-limiting factor. The Strategic Japanese-Swiss Science and Technology Program 2017 devoted to the “Research on Hydrogen as a renewable energy carrier” is a unique and very timely opportunity to merge the complementary scientific and technological cutting-edge expertise of the two groups. The target of this research project is the fabrication, test and optimization of a novel inorganic-biological hybrid system for artificial photosynthesis by coupling an efficient solar-light-sensitive semiconductor and a low-cost stable bacterial biocatalyst.
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