First UK solar to fuels symposium
Meeting report by Leo Salter
ECG Committee Member
ECG Bulletin July 2012
ECG Committee Member
ECG Bulletin July 2012
A report of the meeting held at the RSC’s Chemistry Centre in London on January 18th 2012.
The First UK Solar to Fuels Symposium (see http://www.rsc.org/ConferencesAndEvents/RSCConferences/Solar/index.as) was organised by the Environment, Sustainability and Energy Division (ESED) with the support of the Dalton Division, the Faraday Division and the Materials Chemistry Division; it was also sponsored by RSC Publishing under the auspices of the journal Energy and Environmental Science. The aim of the one-day symposium was to provide an opportunity for the growing interdisciplinary UK solar-to-fuels research community to address the challenges of using sunlight to drive the synthesis of molecular fuels. An RSC report of the research area, “Solar Fuels and Artificial Photosynthesis: Science and Innovation to Change our Future Energy Options”, is available at www.rsc.org/solar-fuel.
The importance of this topic was underlined by a brief presentation (“US Perspective on Solar to Fuels: How We Got to Where We Are”) given by Raymond Orbach (Director of the Energy Institute, University of Texas at Austin). He described a recent competition, set up by the US Department of Energy, in which institutes competed for $122 million to set up a “Sunlight Energy Innovation Hub”. The Hub was to focus on creating a prototype device to produce fuel from the sun ten times more efficiently than plants. The competition was won by the Joint Centre for Artificial Photosynthesis at Caltech (which led a consortium of Californian university and research institutions). The bidding process energised and developed the research community involved in solar to fuel.
In opening the proceedings, James Durrant (Imperial College, London) described a resurgent and expanding UK community that needed more coherence and a clear vision for sunlight to fuels technology and explained that the meeting was an attempt to establish and support such a community. Bill Rutherford (Imperial College, London) then spoke on “Artificial Photosynthesis – What Can We Learn From the Natural Kind?” He deconstructed the problem into three components—the conversion of light into chemical energy, the storage of the chemical energy so produced, and the processes of light collection—and then linked these to the natural processes involving Photosystems I and II. He did, however, point out that the use of semiconductor systems for artificial photosynthesis meant that the properties of natural reaction centres such as Photosystems I and II had limited relevance. For more details on the chemical challenges in solar energy utilization see http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1635072/pdf/zpq15729.pd.
The First UK Solar to Fuels Symposium (see http://www.rsc.org/ConferencesAndEvents/RSCConferences/Solar/index.as) was organised by the Environment, Sustainability and Energy Division (ESED) with the support of the Dalton Division, the Faraday Division and the Materials Chemistry Division; it was also sponsored by RSC Publishing under the auspices of the journal Energy and Environmental Science. The aim of the one-day symposium was to provide an opportunity for the growing interdisciplinary UK solar-to-fuels research community to address the challenges of using sunlight to drive the synthesis of molecular fuels. An RSC report of the research area, “Solar Fuels and Artificial Photosynthesis: Science and Innovation to Change our Future Energy Options”, is available at www.rsc.org/solar-fuel.
The importance of this topic was underlined by a brief presentation (“US Perspective on Solar to Fuels: How We Got to Where We Are”) given by Raymond Orbach (Director of the Energy Institute, University of Texas at Austin). He described a recent competition, set up by the US Department of Energy, in which institutes competed for $122 million to set up a “Sunlight Energy Innovation Hub”. The Hub was to focus on creating a prototype device to produce fuel from the sun ten times more efficiently than plants. The competition was won by the Joint Centre for Artificial Photosynthesis at Caltech (which led a consortium of Californian university and research institutions). The bidding process energised and developed the research community involved in solar to fuel.
In opening the proceedings, James Durrant (Imperial College, London) described a resurgent and expanding UK community that needed more coherence and a clear vision for sunlight to fuels technology and explained that the meeting was an attempt to establish and support such a community. Bill Rutherford (Imperial College, London) then spoke on “Artificial Photosynthesis – What Can We Learn From the Natural Kind?” He deconstructed the problem into three components—the conversion of light into chemical energy, the storage of the chemical energy so produced, and the processes of light collection—and then linked these to the natural processes involving Photosystems I and II. He did, however, point out that the use of semiconductor systems for artificial photosynthesis meant that the properties of natural reaction centres such as Photosystems I and II had limited relevance. For more details on the chemical challenges in solar energy utilization see http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1635072/pdf/zpq15729.pd.
After lunch Robin Perutz (University of York) spoke on “A Porphyrin – Rhenium Dyad versus Two Monomers: Reduction of CO2”. Starting from the known properties of rhenium bipyridine tri-carbonyl species as photocatalysts for carbon dioxide reduction in the UV, he went on to describe the synthesis, characterisation and examination of similar species as photocatalysts at visible and longer wavelengths. A dyad in which rhenium tricarbonylbipyridine was linked through an amide bond to a zinc tetraphenylporphyrin was investigated in relation to its ability to reduce carbon dioxide to carbon monoxide. Detailed analysis showed that two separate photochemical steps were occurring, that the separate components were more efficient than the dyad, that yields (turnover) were probably limited by fast electron transfer, and that the porphyrin was reduced to chlorine (which was shown to have been produced concomitantly).
Erwin Reisner (University of Cambridge) then gave a paper entitled “Solar water splitting with catalysts integrated in nanostructured metal oxide materials”. He described the assembly of functional hybrid materials, in which molecular catalysts are integrated in nanostructured metal oxide materials to enhance the rate and selectivity of fuel-forming reactions. For example, attachment of hydrogenase or a synthetic cobalt complex on ruthenium dye-sensitised TiO2 nanoparticles enhances the rate of proton production by two orders of magnitude during visible light irradiation in the presence of a sacrificial electron donor.
Erwin Reisner (University of Cambridge) then gave a paper entitled “Solar water splitting with catalysts integrated in nanostructured metal oxide materials”. He described the assembly of functional hybrid materials, in which molecular catalysts are integrated in nanostructured metal oxide materials to enhance the rate and selectivity of fuel-forming reactions. For example, attachment of hydrogenase or a synthetic cobalt complex on ruthenium dye-sensitised TiO2 nanoparticles enhances the rate of proton production by two orders of magnitude during visible light irradiation in the presence of a sacrificial electron donor.
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Christopher Pickett (University of East Anglia) talked about “Photoelectrocatalysis at p-type silicon: CO and H2 generation with dithiolene, porphyrin and phosphine complexes”, explaining that “visible light-driven photoelectrochemical conversion of carbon dioxide to carbon monoxide, or of protons to dihydrogen, are half-cell reactions of relevance to the use of carbon dioxide as a C1 feedstock and to the generation of hydrogen as a solar fuel.” Fundamentally the challenges are to design catalysts that can approach (or even exceed) the efficiencies of natural systems in driving energetically uphill redox catalysis, and to then anchor such catalysts to the electrode surface to overcome problems caused by localised substrate depletion.
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Pickett described the reduction of organometallic Mo or W complexes on p-type silicon under illumination. [This work is analogous to that of Chorkendorff and coworkers, reported in Nature Materials (2011), 10, 434, who showed that surface bound Mo3S4 centres efficiently catalyse the evolution of hydrogen when coupled to a p-type silicon semiconductor that harvested red photons from the solar spectrum]. The speaker also discussed the use of electrochemical catalysis of carbon dioxide reduction to carbon monoxide in the presence of iron porphyrins. As with much of the work described in the meeting, the issue is one of overcoming the thermodynamic stability of carbon dioxide to convert it into an energy usable form in a way that produces more energy than is used–and preferably only uses energy generated by renewable non-fossil fuel processes.
Lee Cronin (University of Glasgow) spoke on “New Paradigms in Water Splitting”, where the issue is one of storing energy by electrochemically or photochemically splitting water to produce oxygen and hydrogen, using, for instance, water splitting systems embedded into photoelectrodes. Candidates for such splitting systems include model Photosystem II systems. For example, a redox-active polyoxometalate (POM) catalyses the rapid oxidation of water to oxygen. However, the associated protons must also be converted to hydrogen. For further details see www.glasgowsolarfuels.com.
Lee Cronin (University of Glasgow) spoke on “New Paradigms in Water Splitting”, where the issue is one of storing energy by electrochemically or photochemically splitting water to produce oxygen and hydrogen, using, for instance, water splitting systems embedded into photoelectrodes. Candidates for such splitting systems include model Photosystem II systems. For example, a redox-active polyoxometalate (POM) catalyses the rapid oxidation of water to oxygen. However, the associated protons must also be converted to hydrogen. For further details see www.glasgowsolarfuels.com.
Ivan Parker (University College London) also spoke on “Solar water splitting” and looked at the possibilities of using a photodiode to form hydrogen directly from water with subsequent hydrogen and oxygen separation. In this way, “all the energy needs of a typical household would be addressed by photosplitting 5 litres of water a day.” The results indicated that platinum-coated titanium dioxide worked best.
In the concluding talk of the meeting, Peter Edwards (University of Oxford) spoke on “Energy Storage and the Chemical Bond”. He described the chemist’s dream of “the efficient, catalytically-enhanced transformation of carbon dioxide”, in which, using energy taken from renewable sources, carbon dioxide taken from the atmosphere would be used for the closed loop production of carbon-neutral synthetic fuels. Trapping carbon dioxide at source on site with methane to produce syngas or the air capture of carbon dioxide using polyamine supports are possible approaches.
Over a hundred people attended this meeting and it is hoped that it will be the first of a series. Although considerable time was set aside for discussion it was never enough; much thought-provoking commentary occurred throughout the meeting and various emergent technologies were mentioned as being involved in this area and which may become commercially viable in the future (see for instance http://airfuelsynthesis.com). I hope that this report accurately conveys the fascinating multidisciplinary efforts covered in the meeting.
LEO SALTER
Chair, Environment, Sustainability and Energy Division and Vice-Chair, Environmental Chemistry Group
In the concluding talk of the meeting, Peter Edwards (University of Oxford) spoke on “Energy Storage and the Chemical Bond”. He described the chemist’s dream of “the efficient, catalytically-enhanced transformation of carbon dioxide”, in which, using energy taken from renewable sources, carbon dioxide taken from the atmosphere would be used for the closed loop production of carbon-neutral synthetic fuels. Trapping carbon dioxide at source on site with methane to produce syngas or the air capture of carbon dioxide using polyamine supports are possible approaches.
Over a hundred people attended this meeting and it is hoped that it will be the first of a series. Although considerable time was set aside for discussion it was never enough; much thought-provoking commentary occurred throughout the meeting and various emergent technologies were mentioned as being involved in this area and which may become commercially viable in the future (see for instance http://airfuelsynthesis.com). I hope that this report accurately conveys the fascinating multidisciplinary efforts covered in the meeting.
LEO SALTER
Chair, Environment, Sustainability and Energy Division and Vice-Chair, Environmental Chemistry Group
