While the first fuel cell-propelled cars are expected on UK roads in 2015, their success depends to a very large extent on the widespread availability of pure hydrogen fuel and a fuelling infrastructure. The UK government recently announced the provision of £11M for the roll-out of a hydrogen fuelling infrastructure, but hydrogen is currently generated industrially by steam reforming natural gas, an unsustainable process that co-generates carbon dioxide and contributes to global warming. Electrolysis of water is by far the most sustainable method for generating pure hydrogen and the major technologies under development are (i) alkaline electrolysis, (ii) high temperature solid oxide electrolysis, and (iii) proton exchange membrane (PEM) electrolysis. However, each of these technologies suffers from serious economic, technological, and/or safety limitations. Intermediate-temperature PEM electrolysers operate in the temperature range 150-300 celsius and offer significant advantages over other electrolysers, including potentially lower running costs, the ability to deliver compressed hydrogen, and high thermodynamic efficiencies. However, to capitalise on these advantages, a number of issues must still be addressed; in particular, the performance and stabilities of PEMs in the intermediate-temperature range must be improved and the reliance of these devices on noble-metal catalysts must be mitigated. In this project, we aim to solve both of these problems by developing a new generation of PEM electrolysers that contain proton-conducting ionic liquids as the electrolyte. The use of these materials as proton conductors within PEMs will allow us to use non-precious, Earth-abundant electrocatalysts to effect hydrogen and oxygen evolution, and to solve the stability issues hampering state-of-the-art PEM electrolysers, advances that will lead to a step-change in PEM electrolyser technology.

Fuel cells have been promoted as a pollution free alternative for energy generation when converting hydrogen into electricity. There are several constraints which have limited the implementation of this technology and this proposal addresses all of the major problems. To make hydrogen requires energy and using conventional methods requires electricity to electrolyse water, if the electricity comes from fossil fuels then the problem is simply moved rather than solved. To use renewable energy requires electrolysers where the energy intermittently generated by the source (wind, solar, tidal etc) is converted into hydrogen at source by an on-site Polymer Electrolyte Membrane (PEM) Electrolyser. The problem with PEM electrolysers is that the membrane used needs to be thick to prevent hydrogen mixing with oxygen to form an explosive mixture but the thickness of the membrane reduces efficiency. Similar problems manifest themselves in fuel cells, the conversion of hydrogen back into electricity requires a PEM fuel cell, the membrane is the same as in the electrolyser and again needs to be thick to prevent fuel crossover but this again reduces efficiency. A third technology, the Direct Methanol Fuel Cell (DMFC) was developed to address the problems around hydrogen storage but again the membrane is the same and again thickness and fuel crossover constrain the efficacy of the membrane. In this work we intend to take the properties of the graphene and hexagonal boron nitride (hBN) which have been proven to allow protons to pass but prevent all other transport of materials and apply them to the three technologies discussed. The materials challenges around the manufacture of a defect free barrier membrane will be tackled with the added benefit of utilising the expensive platinum catalyst more efficiently. The potential benefit of this work is that hydrogen production will become more efficient and the cost of converting the fuel into electricity in a fuel cell will decrease as the overall cost of the fuel cell is reduced. This will make viable the use of 'green hydrogen' as an energy storage medium and enable the route to market for PEM fuel cells which are necessary to convert the hydrogen (and other fuels such as methanol) into electrical energy. Another potential benefit of this study is the complete replacement of the membrane material by a supported graphene or hBN. This will facilitate the reduction in volume of a fuel cell, as the fuel will no longer need to be humidified so there will be fewer components, which is important for mobile/portable applications.

There is an urgent need to address the accelerating increase in global CO2 emissions and atmospheric CO2 levels while providing fuels to meet growing energy needs. The UK government has targeted an 80% reduction in emissions (from 1990 levels) by 2050 with an interim target of 34% reduction by 2020. Increasingly, it is becoming clear that a key approach to storage of variable sustainable energy sources such as solar or wind power is in the form of stored chemical energy, and that this is likely to be as a form of hydrogen. However, although hydrogen itself has excellent enthalpy content per unit weight, it is a low density gas, has storage difficulties, and requires relatively high compression energy. The present proposal is focused on the conversion of sustainably produced hydrogen to high energy density liquid fuels including methanol, DME and hydrocarbons which are more easily transported and are compatible with existing fuel distribution networks. These fuels are low in sulfur and flexible in their contribution to future low carbon-intensity fuel scenarios by displacing fossil sources from the liquid fuels pool. They can be used for transport fuels (where they are likely to remain the focus for some time to come), as blending components, as seasonal storage candidates (exploiting their permanence and energy density), for distributed power production or for local heating. The synthesis of these liquid fuels will be achieved using CO2 as a vector to react with hydrogen from solar or wind inputs. We therefore aim to develop new technology to reduce the atmospheric CO2 burden by utilising only water as a source of this hydrogen, avoiding highly endothermic thermocatalytic steam reforming. The annual CO2 emissions from UK electricity generation (around 150x10^6 tonnes) is sufficient, in principle, to supply the UK requirement for liquid transportation fuels, or three times the amount required for the world annual production of methanol (around 45x10^6 tonnes). There are a number of possible attractive concentrated point sources of this CO2, including CO2 prepared for sequestration or from ammonia plants, which could be used to make liquid fuels in the medium term provided efficient catalytic technologies could be developed. Thus we will develop new catalytic technology for the production of synthesis gas (CO/H2) and simple fuel organics, ultimately driven by solar energy using CO2 and H2 sustainably produced from water. We will explore integration of hydrogen and syngas generation with production of syngas from biogenic sources such as waste or biomass to provide additional feed flexibility. Part of our work will develop novel and targeted catalysts for the thermocatalytic production of 'green' fuels from syngas with variable CO2, H2 and water content, focused by process systems engineering considerations that specifically address low-carbon aspects such as intermittency of primary renewable power in process design. Industry partners have endorsed the approach and will provide key input into the form of point source CO2 supply, catalyst manufacture, liquid fuel synthesis, electrolyser manufacture, sustainable hydrogen generation and technology integration, life cycle analysis and industrial fuel usage. The proposal adopts a multidisciplinary catalyst discovery, deployment and process engineering approach to develop, evaluate and optimise thermal, photo- and electro-catalysed routes to liquid fuels from CO2 and water using solar energy (and, indirectly, wind or marine power). Direct thermal and solar-assisted paths to methanol and DME will be compared with stepwise solar/electrochemical syngas generation plus thermal DME or Fischer-Tropsch hydrocarbon synthesis paths. The novel catalyst chemistries enabling each route will be integrated on the basis of process systems modelling and analysis to identify optimised schemes that will be benchmarked by input from industry partners with key roles in potential supply chains.

The research will create a hybrid anaerobic digestion process in which hydrogen made from renewable energy sources (e.g. wind and photovoltaics) is used to produce biomethane at more than 95% purity. The process therefore provides an efficient in situ biogas upgrading technique which will maximise the conversion of the available carbon in waste biomass into a fuel product that has a wide range of applications, including short-term storage for grid balancing and use as a vehicle fuel. The process is likely to be more environmentally friendly and sustainable than current methods for biogas upgrading as there is reduced process loss of methane. The target is to develop the system for use in the water industry where there is a large potential to integrate it into existing infrastructure and to maximise the use of process heat and other by-products. A second targeted application is at a smaller scale on farms, where there is an abundant supply of waste biomass and a lack of suitable biogas upgrading plant.

This is an extension of the original Fellowship "Spectroscopy-driven design of an efficient photocatalyst for CO2 reduction" There is sufficient solar energy incident on the UK to provide for all of our energy needs. However the insolation level varies hugely both within a day and on a seasonal level. For any energy technology to be viable it is essential that it is reliable. A route to overcoming the intermittency of supply issue is to use the solar energy to drive the production of a chemical fuel which can be stored and transported to be available when and where it is needed. Sustainable carbon-based solar fuels and feedstocks (e.g. CH4, CH3OH, CO) can be produced by the coupling of light driven water oxidation to the reduction of CO2. This is an exciting prospect but to realise the goal of low carbon-intensity fuel economy breakthroughs are required for both fuel generation and utilisation systems. Current materials for CO2 reduction and water oxidation do not achieve the required level of efficiency and stability at a viable cost. Similarly the most promising clean technologies for electricity generation on demand from carbon fuels, fuel cells, often suffer from relatively low efficiencies and intolerances to impurities in the fuel feed. The original fellowship has been highly successful in delivering new low-cost catalysts that can either be driven directly by sunlight (photocatalysts) or indirectly using electrical energy (which could in principle come from a PV panel) to reduce CO2 to CO, an important liquid fuel precursor. Part of the original fellowship developed new capabilities within the UK for a highly sensitive surface sensitive spectroscopy, IR-Vis Sum Frequency Generation Spectroscopy. This experiment has been used to identify with an incredible level of detail the mechanisms of catalysts at surfaces. These, and our wider spectroscopic studies, have been critical in guiding our own catalyst design programme. But the need for mechanistic insights extends beyond our own synthetic programme. A lack of understanding of the mechanisms of catalysis occurring on the surface of electrodes and photoelectrodes is a limiting factor for the entire field preventing the rational development of new materials. Therefore our spectroscopy driven programme will be expanded to address both the crucial reactions of fuel generation (water oxidation and CO2 reduction) as well as to fuel utilisation chemistry, through the study of state of the art metal-oxide fuel cells. The project is ambitious, aiming not just to provide the first identification of all key intermediates during water oxidation on the most commonly studied photoelectrode (hematite), but also to explore how secondary interactions with water and electrolyte salts control the activity. A similar level of mechanistic detail is also sought from leading CO2 reduction catalysts and fuel cell electrodes. This level of mechanistic detail that we aim to deliver could be transformative to our own, collaborators and the wider communities programmes of material development. The delivery of scalable, efficient materials for solar fuels production and utilisation is a challenging goal but the potential impact is enormous. An improved understanding of surface mechanisms on current materials would represent an important step towards this ambition.