Enzymes have established as a new class of catalysts in the field of modern synthetic chemistry and continue to gain in importance. Directed evolution is currently one of the most promising approaches aiming at enzymes with desired catalytic activities and it's potentially directly correlates with the library size that can be screened. One of the most powerful approaches to overcome these limitations is arguable the recently introduced microfluidic droplet technology; this methodology not only allows to quickly screen millions of clones in a cost effective manner, but is also broadly applicable since fluorometric as well as colorimetric assays can be used. Interestingly, even though numerous publication highlight its potential, an unambiguous evidence of its ability to provide synthetically relevant biocatalysts still needs to be furnished. In addition, access to this technology is currently limited to a few academic research groups and thus, this approach requires further implementation to evolve as an easily manageable lab routine in the near future. This project is designed to unite three competencies: i) the expertise of the Hollfelder Group in regarding micro-engineering and protein engineering in droplets, ii) the empirical knowledge of (bio)chemists at Johnson Matthey in view of economically successful industrial applications of biocatalysts and iii) the strong track record of the experienced researched to successfully solve problems at the biology/chemistry-interface. The objective of the project is to perform a proof-of-principle study by improving a well-known alcohol dehydrogenase for the selective desymmetrization of a meso-diol, thereby giving access to a synthetically sophisticated alcohol. In addition, the final aim is not only to obtain an improved mutant which allows to perform the selected biotransformation efficiently, but also a comparison of varying evolution paths differing in the criteria of hit selection between mutagenesis rounds.
With potential widespread uptake of fuel cell technologies in many areas of energy conversion, there is an increasing need to address new ways to reclaim the significant value associated with end-of-life fuel cell stacks. The term fuel cell can be applied to a wide range of electrochemical devices which use a variety of materials; however, the type with potentially the largest market penetration is the polymer electrolyte membrane fuel cell (PEMFC). Although there has been much research into alternatives, the usual electrocatalyst combinations are based on Pt and Ru, both of which are extremely costly. There are several models such as metal leasing which can help address this, but clearly in all cases to facilitate broad market uptake, efficient and effective means of recovery of these metals by a scalable route needs to be developed. Traditional techniques for recovery of these metals, such as pyrometallurgical routes (smelting) has some particular energy and environmental problems as well as constraints which would make large scale recovery of Pt and Ru by these routes impossible. The research proposed here intends to provide the fundamental knowledge required for the development of a process which addresses the following important requirements: 1) Low process cost and complexity 2) Low environmental impact - direct and in terms of emissions from energy input 3) Safe process An electrochemical based closed loop process is proposed which short cuts a lot of the extraction steps to give selective recovery of each metal constituent in turn. The idealised process consists of two coupled reactors, the leach reactor in which the metals are dissolved selectively and a membrane divided electrochemical reactor, in which the metals are deposited sequentially from solution whilst the oxidant is regenerated simultaneously. This process in conjunction chemical systems to be investigated to facilitate it will produce a much safer and more energy efficient process which could significantly reduce the lifecycle costs of fuel cells. However, there are some real challenges that have to be addressed before a practical process could be deployed. The project will explore in detail: 1) The leaching kinetics and mechanisms for these metals and how intimate lamination of the catalyst layers into the membrane affects recovery rates. 2) Whether there is sufficient access to the precious metal through the pore structures of the carbons used when the catalyst has been laminated without the need for a membrane dissolution or partial dissolution process 3) Selective and sequential recovery of each metal component which will require detailed investigation into the deposition kinetics of each metal and design of a suitable cathode for the electrochemical reactor Fuel cells promise to be a significant part of the future energy conversion market, playing a key role in the decentralisation and diversification of UK electricity generation, finding application in remote and combined heat and power (CHP) systems. The UK has some significant interests in the complete supply chain from raw materials to system integrators with range from small SMEs such as Intelligent Energy and Acal Energy, to large multinationals such as Centrica and Johnson Matthey. If the example is taken of a fuel cell micro-CHP system, to displace the current condensing boiler technology, then the UK market is worth around 1.5 M units per year. To support this shift in technology, complementary supply and reclamation routes clearly need to be established now to help the most efficient and successful uptake of the technology. If successful this research, by reducing life-cycle costs, could quicken the introduction of Fuel Cells in many applications.
Despite the high thermodynamic stability of CO2, biological systems are capable of both activating the molecule and converting it into a range of organic molecules, all of which under moderate conditions. It is clear that, if we were able to emulate Nature and successfully convert CO2 into useful chemical intermediates without the need for extreme reaction conditions, the benefits would be enormous: One of the major gases responsible for climate change would become an important feedstock for the chemical and pharmaceutical industries! Iron-nickel sulfide membranes formed in the warm, alkaline springs on the Archaean ocean floor are increasingly considered to be the early catalysts for a series of chemical reactions leading to the emergence of life. The anaerobic production of acetate, formaldehyde, amino acids and the nucleic acid bases - the organic precursor molecules of life - are thought to have been catalyzed by small cubane (Fe,Ni)S clusters (for example Fe5NiS8), which are structurally similar to the surfaces of present day sulfide minerals such as greigite (Fe3S4) and mackinawite (FeS).Contemporary confirmation of the importance of sulfide clusters as catalysts is provided by a number of proteins essential to modern anaerobic life forms, such as ferredoxins, hydrogenases, carbon monoxide dehydrogenase (CODH) or acetyl-coenzyme A synthetase (ACS), all of which retain cubane (Fe,Ni)S clusters with a greigite-like local structure, either as electron transfer sites or as active sites to metabolise volatiles such as H2, CO and CO2. In view of the importance of (Fe,Ni)S minerals as catalysts for pre-biotic CO2 conversion, we propose employing a robust combination of state-of-the-art computation and experiment in a grand challenge to design, synthesise, test, characterise, evaluate and produce for scale-up novel iron-nickel sulfide nano-catalysts for the activation and chemical modification of CO2. The design of the (Ni,Fe)S nano-particles is inspired by the active sites in modern biological systems, which are tailored to the complex redox processes in the conversion of CO2 to biomass.The scientific outcome of the Project will be the design and development of a new class of sulphide catalysts, tailored specifically to the reduction and conversion of CO2 into chemical feedstock molecules, followed by the fabrication of an automated pilot device. Specific deliverables include:i. Atomic-level understanding of the effect of size, surface structure and composition on stabilities, the redox properties and catalytic activities of (Fe,Ni)S nano-catalysts;ii. Development of novel synthesis methods of Fe-M-S nano-clusters and -particles with tailored catalytic properties (M = Ni and other promising transition metal dopants);iii. Rapid production and electro-catalytic screening of lead nano-catalysts for the activation/conversion of CO2;iv. Development and application of a new integrated design-synthesis-screening approach to produce effective nano-catalysts for desired reactions;v. Construction of a prototype device capable of catalysing low-temperature reactions of CO2 into products at typical low-voltages, that can be obtained from solar energy; vi. Identification of optimum process for scale-up in Stage 2, from the Economic, Environmental and Societal Impact evaluationThe target at the end-point of Stage 1 is the fabrication of a photo-electrochemical reactor capable of harvesting solar energy to (i) recover CO2 from carbon capture process streams, (ii) combine it with hydrogen, and (iii) catalyse the reaction into product. In Stage 2 of the project, the prototype will be developed into a scaled-up commercially viable device, using optimum catalyst(s) in terms of (i) reactivity/selectivity towards the desired reaction; (ii) economic impact; and (iii) environmental, ethical and societal considerations.
The drive towards more sustainable technologies relies on developing improved catalytic materials; greater activity and selectivity to desired products with ever decreasing amounts of expensive catalyst metals. Supported metal nanoparticles are a cornerstone within the field of heterogeneous catalysis; the metal support interaction aids the stability of the catalyst and promotes chemical reactions. Controlling the interface of composite structures is a key part of this synergy between metal nanoparticle and metal oxide support. Supported metal nanoparticles are most commonly prepared by the impregnation of metal oxide hosts, followed by a thermal activation. The concept of the project is to use metal nanoparticles supported on MOFs as templates. The intention is to remove the organic linkers through chemical means, i.e. by introducing strong reductants such as NaBH4, producing tailored nanocomposites. Indeed, we have recently performed a proof-of-concept study where we were able to prepare PdCu/Cu2O nanocomposites from Pd/Cu-BTC templates. The programme of work will: (i) Show how systematic variations to preparation conditions influences the composite structure. (ii) Demonstrate their importance for emerging catalytic applications in sustainable energy generation (i.e formic acid decomposition). (iii) Use advanced characterisation under process conditions to understand the formation of the composite structure and how the structures evolve during catalysis.