Diamond Concise Annual Review 2019/20

T he Diamond Spectroscopy Group is built around four beamlines; the Microfocus Spectroscopy beamline (I18) the Core X-ray Absorption Spectroscopy (XAS) beamline (B18) and the two independently operating branches of the Versatile X-ray Absorption Spectroscopy beamline, I20-Scanning and I20-EDE (Energy Dispersive EXAFS). These four beamlines are complementary in many aspects, such as the energy range they cover, the size of the focussed beam spot delivered to the sample, and the time resolution they are able to reach. This complementarity means that they can support research across many different scientific disciplines, from chemistry and catalysis through to materials science, condensedmatter physics, environmental and life science, energy materials and cultural heritage. In the past year studies have included a breakthrough in identifying colour in fossils, improving catalysts in industrial processes, and optimising battery design for electric vehicles. Identifying colour from fossils Researchers using beamline I18 at Diamond have achieved a breakthrough in the ability to resolve fossilised colour pigments. Although colour has played a vital role in evolution, techniques to study fossils were not able to identify pigmentation until now. The research teammapped key elements associated with the pigment melanin in an extinct, three million-year-old species of mouse. Different forms of melanin can give rise to a black or dark brown colour (eumelanin), or a reddish or yellow colour (pheomelanin). Using X-ray Absorption Spectroscopy and X-ray Absorption Near Edge Structure Spectroscopy (XANES) the research team was able to discern the trace metals in the pigments and to reconstruct the reddish colour in the mouse’s fur.They were able to determine that the fossilised mouse fur incorporated trace metals in the same way that trace metals bond to pigments in animals with red fur.Their work provides a new chemical method for resolvingmelanin pigments in both recent and extinct tissue (e.g. hair, skin, feather) samples. These results should allow reconstruction of extinct animals with more confidence. Manning PL et al . doi: 10.1038/s41467-019-10087-2 Optimising catalysis Catalysts play an important and growing role in industrial processes, notably the removal of harmful pollutants from vehicle exhausts. Ongoing innovative research is needed to discover how they work in order to design more cost-effective and efficient products. A research team fromUK universities studied the oscillations seen during carbon monoxide oxidation by developing a reactor that measured X-ray absorption fine structure (XAFS) and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) simultaneously. Using the I20-EDE beamline, the team were able, for the first time, to observe the structural changes that drive the oscillatory performance of the palladium nanoparticles used as a catalyst. They found that the changes were localised to a minor component of the overall catalyst profile. The experiment confirmed that new methods for probing catalyst behaviour in both space and time are needed to truly understand catalysis. These methods will allow for better design of catalytic processes for environmental protection, emerging energy technologies, and the production of sustainable chemical feedstocks. Dann EK et al. doi: 10.1016/j.jcat.2019.03.037 Improving the performance of electric vehicles It is expected that electric vehicles (EVs) powered by batteries will replace the internal combustion engine by 2050. Despite impressive progress over the last decade, several technological hurdles still need to be overcome to make EVs practical and economical. One of the major challenges to the EV industry is the limited driving range of the cars which is dictated by the energy density of the battery pack. This, in turn, is governed by the number of electrons that can be exchanged per transition-metal (TM) cation in the cathode materials. Currently, the state-of-the-art cathode materials used in EV exchange less than one electron per TM cation. One strategy being explored to improve energy density is to use intercalated compounds capable of multiple electron transfer per TM cation. Vanadyl phosphates (VOPO 4 ) are an appealing class of compounds, since they offer two- electron exchange within the voltage window that is safe and suitable for EV applications. Researchers at Diamond used core X-ray Absorption Spectroscopy (XAS) at beamline B18 to directlymonitor the vanadiumoxidation state of ε-VOPO 4 . This technique was vital to identify any side reactions promoted by high energy ball milling-induced disorder which affects the electrochemical performance of the cathodes. The results highlighted the challenges associated with improving the performance of batteries and recent work with a ball-milling free approach demonstrated full intercalcation without any indication of side reactions. The study shows the importance of synchrotron studies in battery research to identify detrimental side reactions in cathodes that would otherwise go undetected. Rana J et al. doi: 10.1039/C8TA06469E D I A M O N D L I G H T S O U R C E A N N U A L R E V I E W 2 0 1 9 / 2 0 D I A M O N D L I G H T S O U R C E A N N U A L R E V I E W 2 0 1 9 / 2 0 24 25 Spectroscopy Group