Global warming due to excessive CO2 emissions and fossil fuel depletion have urged the development of clean and cheap energy technologies to satisfy the ever-increasing energy demand and net reduction in CO2 emissions. Strategies to utilise CO2 captured from sources such as fossil fuel-based power stations are urgently required to mitigate climate changes. Renewable energy production is likely to be the cleanest method of producing electricity. However, renewable electricity generation through the use of solar, wind or tidal energy transfer is notoriously intermittent and can be inefficient on overcast, still days and non-existent between tides during still days. Developing technologies that are composed of diverse energy sectors including renewables, fuel cells and electrolysis cells is thus vital to fulfil efficient and flexible low carbon energy storage and conversion. This project will seek to explore and develop the recently discovered materials in diverse electrochemical devices for efficient energy storage and conversion. This include converting CO2 into value added fuels and producing electricity using practical hydrocarbons or biogas. The CO2-derived fuels can be regarded as a storage medium for excess renewable electricity supply, when excess renewable electricity is used to drive the CO2 conversion. These fuels have high energy density, are easy to store and transport, and are compatible with the existing fossil fuel infrastructure that hydrogen (H2) fuels are incompatible with. Additionally, the CO2-derived fuels can in turn be used to generate electricity when the renewables are "down", allowing extra fuelling to the system. The CO2 conversion device proposed can split steam and CO2 in the same flow, producing syngas (CO and H2) which is the feedstock for industrial synthetic fuel production. Further, the same device can reversibly work as a fuel cell to generate electricity. The materials used in these devices are critical to their output. Conventional fuel electrode materials (a mixture of nickel (Ni) and zirconia) have limitations due to their poor stability and durability under realistic fuel environments. Materials development in recent years has been focusing on alternative oxides preferably with the active components at nanoscale to maximise activity. The most exciting recent discovery is a group of titanate perovskites (with a formula ABO3), where their B-site metal, e.g. Ni, can move out of the perovskite lattice as the ambient conditions change. This exsolution of catalysts (metal, alloy, oxide) from the host lattice upon reduction can be used to decorate the electrode surface with nanoparticles offering high catalytic activity. Further, the exsolved nanoparticles are anchored to the surface of the parent perovskite, which makes them considerably more stable than catalysts added by conventional means. Nevertheless, the research on these materials in real electrochemical devices so far has been very limited. The project will seek to deliver exsolution materials processing approach for CO2 conversion to maximise performance. The methodologies to drive exsolution of nanocatalysts during CO2 electrolysis operations will be developed. Conversion of steam and CO2 in the same flow will be also investigated using these materials, with specific focus on generating products with desirable CO/H2 ratios for industrial fuels synthesis. Finally, switching the electrolyser to fuel cell using realistic hydrocarbons or biogas fuel will be conducted, aiming to advance the development of a low carbon electricity generation system with significant robustness and cost-competitiveness. The overall objective is to develop and demonstrate a novel, efficient, flexible and robust technology as one that can realise both the fuel production through CO2 conversion and low carbon electricity generation, to help addressing utilisation of sustainable renewable energy and CO2 recycling for fuel production and climate mitigation.

Solid oxide fuel cells are highly intricate devices with many interfaces which are typically formed at high temperatures. This places many constraints in terms of chemical and physical compatibility upon such devices limiting both performance and durability. Such problems strongly restrict materials choice and impose significant cost penalties on SOFC manufacture. The utilisation of solution methods to introduce part of the SOFCs active constituents is a highly attractive approach that has gained much interest in recent years. This can involve infiltration of nanoparticles or impregnation of precursor solutions to form phases in situ. Much lower reaction temperatures can be utilised avoiding problems with compatibility and affording wider materials choice. Typically such process involves formation of a scaffold structure by high temperature processing and then impregnation of an electrode by lower temperature methods. We have successfully applied this approach to three different novel variants of SOFC architectures. These are electrolyte supported oxide anodes, oxide anode supported and metal anode supported cells. Excellent performances can be obtained and good redox properties demonstrated; however, progress needs to be made to ensure high durability. The impregnates tend to form well dispersed nanoparticles, but these might be expected to agglomerate over time, in fuel cell operating conditions, to reduce overall performance. Through the national and European projects where we applied the impregnation concept, we have learned much about impregnation and how to develop appropriately dispersed electrode structures. The electrode structure is seen to evolve with use and clear opportunities exist to optimise structures through improved processing. Most important has been the realisation that there are strong interplays between the materials impregnated, the substrate and the solvent utilised. Even subtle changes in electrode composition, demand significant changes in impregnation chemistry to maintain the maximum levels of performance. In this project we seek to further develop control of this impregnation chemistry and hence to develop generic methods for developing controlled microstructures via solution routes across several platforms. These new chemistries will be applied to electrolyte- and anode-supported SOFC geometries and properties optimised for performance, durability and redox tolerance. The overall objective is to develop and demonstrate this new approach as one that can be successfully applied to manufacture of fuel cells that combine high performance with durability and resistance to contaminants. We will apply this approach typically for an impregnated oxide electrode with metallic catalyst to zirconia, strontium titanate and metal supports and develop our understanding of the fundamental chemistry across this range of platforms. By so doing we will develop methodologies to tailor impregnations over a broad range of composition space. Studies of performance, durability and resistance to contaminants utilising electrochemical, spectroscopic and microstructural techniques will be used to inform choice of impregnate systems. Final outcomes will be delivery of novel tailored chemistries for different SOFC application modes and geometries, demonstration of novel cell technologies with robust, high performance characteristics at SOFC developer ready scales and development of new routes and instrumentation for SOFC manufacture.

In recent work we have identified a very powerful and extensive phenomenon, the constrained production of nanoparticles that opens up a new field impinging on chemistry, materials science and physics. The dispersion, stability, versatility and coherence with the substrate impart quite significant properties to the emergent nanoparticles opening up a major new topic. The process is driven by the lattice decomposition of a metal oxide under reduction by various means. Conventional thinking considers this as a simple phase separation; however, by careful control of the defect chemistry and reduction conditions, a very different process can be achieved. These nanoparticles emerge from the substrate in a constrained manner reminiscent of fungi emerging from the earth. The emergent nanoparticles are generally dispersed evenly with a very tight distribution often separated by less than one particle diameter. Here we will explore the composition and reaction space conditions necessary to optimise functionality, structure and applocability. We will also seek to better understand this phenomenology relating to correlated diffusion, driving energetics and mechanism of emergence. Further work is necessary to understand the critical dependence of composition in a very extensive domain of composition space depending upon charge and size of the A-site cations, oxygen stoichiometry and transition metal redox chemistry. Of particular importance is to understand the nature of the interaction between the nanoparticle and the substrate addressing the evolution of the nanoparticles from the surface and how the particles become anchored to the substrate. Exolved metals can react to form compounds whilst maintaining the integrity of the nanostructural array and this offers much potential for further elaboration of the concept. We will investigate the important catalytic, electrocatalytic and magnetic physics properties arising at constrained emergent particles, driven by dimensional restriction. Emergent nanomaterials provide very significant surface-particle interactions and promise new dimensions in catalysis. The electrochemical reactions in devices such as batteries and fuel cells are restricted to the domain very close to the electrolyte electrode interface. Emergent materials can be applied in exactly this zone.