Climate Change Literature review 2021

Many studies conducted at Diamond are helping to improve our understanding of the core environmental processes and their implications. This is a complex area, with all human activity having an environmental impact to some extent. For example, the drive to reduce carbon emissions will have significant impacts in other areas, such as the challenge to source sufficient key materials for batteries for electric vehicles. In the same way, the use of nuclear energy, although low on direct carbon emissions, will have significant environmental impact for generations to come and needs to be fully understood.  

Numerous studies at Diamond are providing potential solutions to some of the most significant environmental challenges we face. 

In 2016 a species of bacteria (Ideonella sakaiensis) was found to degrade polyethylene terephthalate (PET) which is one of the most abundant plastics found in food and drink packaging and clothing. Research by a US/UK group has provided valuable information to further understand the biological degradation of this type of plastic. They used Macromolecular Crystallography (MX) on beamline I03 at Diamond (along with I23 and I04 in a previous study – Austin HP et al. PNAS 2018)¹ to characterise the structure of MHETase, one of the key enzymes involved in breakdown of PET (Knott BC et al. PNAS 2020)² . This work adds valuable data in the efforts to design industrial scale methods to dispose of and effectively reuse this damaging plastic.

Two studies have shown the progress being made in capturing and storing carbon dioxide. Highly absorbent metal-organic framework materials show promise in carbon capture and storage.  A new UK/Russian collaborative study shows excellent high-pressure uptake of carbon dioxide by the new material MFM-160a. The study used the Small-Molecule Single-Crystal diffraction beamline (I19) to determine the material’s performance (Trenholme W et al. J Am Chem Soc 2021)³. 

Another method of capturing and storing carbon dioxide is to inject it into shale reservoirs following extraction of natural gas. An international study group used advanced imaging techniques to quantify the microstructure and pore system of Bowland shale in 3D. Synchrotron source X-ray Computed Tomography (XCT) on Diamond’s Joint Engineering and Environmental Processes (JEEP) beamline (I12) and its Imaging and Coherence beamline (I13) allowed the team to assess the feasibility of carbon storage in what is the largest shale gas reservoir in the UK (Ma L et al. Energy & Environmental Science 2021)⁴ .  

Pioneering work is ongoing to improve the design of the wall flow filters used in vehicle engines to reduce particulates being released into the atmosphere. A research team from the University of Manchester and Diamond demonstrated a new method and first experimental demonstration of time resolved in situ XCT (or micro-XCT) to study aerosol filtration (Jones MP et al. Materials 2020)⁵. This novel image-based method on beamline I13’s Imaging branchline (I13-2) gave valuable insights into how the filter’s pore structure and function evolves during use and has potential for the study of a wide range of dry aerosol filter to reduce air pollution.

Industry, mining and intensive farming practices can result in severe soil pollution, particularly with harmful metals. However, some plant species which thrive on contaminated land are being used in a process termed phytoremediation to improve soil conditions. Cynara cardunculus, a native of southern Europe, has multiple uses including as food and bioenergy and is being studied for its value in phytoremediation. A recent study at Diamond analysed the plant under different levels of stress from metal pollution, using X-ray Absorption Spectroscopy (XAS) on Diamond’s Core EXAFS (Extended X-ray Absorption Fine Structure) beamline (B18) to understand uptake and detoxification mechanisms (Leonardi C et al. Env Sci Poll Res 2021) ⁶. One genotype (C. cardunculus L. var. sylvestris) accumulated high levels of arsenic and cadmium, and tolerated metal toxicity during its growth.  Future studies will focus on this genotype in the efforts to remediate polluted soils and as a potential source of bioenergy. 

Another study by an international research group led by the University of Oxford (White MD et al. PNAS 2020)⁷ is looking at how to improve the resilience of plants to low oxygen levels (hypoxia) caused by flooding and water logging which is becoming increasingly prevalent due to climate change. Plant cysteine oxidases (PCOs) are oxygen-sensing enzymes which control adaptive responses to flooding and could provide a key to engineering plants with enhanced flood tolerance. The group used MX on beamlines I02, I03 and I04 to investigate how the three-dimensional structure of PCO from a member of the brassica family Arabidopsis relates to its ability to trigger hypoxic adaptation. The work provides a platform to improve the ability of crops to withstand future climate extremes and protect global food resources. 

Use of neonicotinoid insecticides has resulted in severe contamination in water sources, despite their benefits in improving crop yield.  A recent study from a joint Spanish/Italian research group has shown the effectiveness of metal-organic frameworks (MOFs) in removing these unwanted insecticides from water (Negro C et al. ACS Appl Mater Interfaces 2021)⁸ . The study characterised the crystal structure and function of MOF using small molecule single crystal diffraction on beamline I19 at Diamond. One newly designed MOF (MTV-MOF 5) was particularly efficient in the process as well as being highly stable and low cost.  This MOF can now be developed as a solution to damaging insecticide pollution in rural water courses. 

Chernobyl Nuclear Power Plant.

The growing contribution of nuclear energy has significant global environmental impact, particularly in terms of storage. Disasters at Chernobyl in 1986 and Fukushima in 2011 have been wake-up calls to the international community but have also provided a valuable research field for the safer use of nuclear power. 

A number of studies at Diamond have examined the fate and impact of radioactive waste, in order to provide long-term storage and disposal methods. Decommissioning of the damaged Chernobyl reactor remains a top global priority and robotic systems are being designed to safely decommission the site. This requires improved knowledge of the properties and behaviour of the hazardous materials formed during the accident. A study conducted by a combined team of UK university departments (Paraskevoulakos C et al. Materials & Design 2021)⁹ designed simulated samples of the Chernobyl lava-like fuel-containing materials (LFCM) which they studied with high-resolution XCT on I12. The study showed differences in porosity and stiffness of the different brittle hazardous materials at the site and will aid the design of appropriate clean up processes. 

An international research group led by Kyushu University, Japan used the Hard X-ray Nanoprobe beamline (I14) to study new radioactive particles found 4 km north of the damaged Fukushima nuclear plant and showed that these particles had a negligible health impact for humans (Marooka K et al. Science of the Total Environment 2021)¹⁰. The study also provided valuable insights into the physio-chemical phenomena that occurred during reactor meltdown. 

An international group led by the University of Manchester have been studying the fate of uranium when stored underground (Townsend LT et al. Chemosphere 2021)¹¹. Previous studies have shown that biogeochemical processes in the ground interact with uranium and alter its behaviour. One of these processes, called sulfidation, results in a uranium sulphide complex which transforms further into highly immobile uranium oxide nanoparticles. The group used the Scanning branchline of the Versatile XAS beamline (I20) at Diamond and simulated conditions representative of a deep underground environment to show that this process took about 10 months. This work will further aid the accurate prediction of the behaviour of uranium during geological disposal.  

Important work is also ongoing on the fate of radioactive materials in the marine environment. Naturally-occurring radium from the leaching of uranium and thorium from reservoir rock is present in many water effluents from extraction processes at oil and gas platforms. Another team from the University of Manchester (Ahmad F et al. Chemosphere 2021)¹² studied the fate of this material in order to minimise environmental impact. The study included solid phase characterisation of marine samples using Core EXAFS on beamline B18 and identified radiobarite particles with a significant portion of radium which can be deposited in marine sediments. This will allow better design of extraction processes to minimise damage to the marine environment.  

Intensive research is ongoing to provide cleaner and more sustainable environmental processes in the future. 

Fuel cells to generate electricity and to power vehicles are likely to play a key role in meeting future net-zero carbon emission targets, but these cells are currently inefficient and expensive to produce. Great progress is being made in reducing costs and improving the efficiency of the catalysts used in fuel cells. Non-precious metal-nitrogen-carbon catalysts are showing promise and a research team from several UK universities (Feng J et al. Adv Function Mat 2021)¹³ used Core EXAFS on B18 and the Small Angle X-ray Scattering (SAXS) and Diffraction beamline (I22) to gain a greater understanding of the catalyst structure and mechanisms. This work will provide the data to further improve the surface area of this type of catalyst and unlock its full catalytic potential. 

Huge demand for expensive lithium-ion batteries has stimulated the search for cheaper and more abundant source materials. Potassium is a promising alternative and red phosphorus has shown strong theoretical application as an anode material; however, it has severe limitations.  A team from the University of Oxford studied a new composite of red phosphorus with graphite using Ptychographic XCT on I13’s Coherence branchline (I13-1) to demonstrate early good electrochemical performance and effectiveness as a novel anode material which now requires further study (Capone I et al. Materials Today Energy 2021)¹⁴ . 

Detailed understanding of the structure and underlying processes in lithium-ion batteries and their cathode materials to improve their longevity and performance is a key area of research at Diamond. Although nickel-rich cathode materials are some of the most promising candidates for lithium-ion batteries their degradation mechanisms are still poorly understood. A team from the University of Cambridge worked on Diamond’s High Resolution Powder Diffraction beamline (I11) to identify a mechanism responsible for battery fatigue and for producing a lowered accessible state of charge (Xu C et al. Nature Materials 2021)¹⁵. The researchers expect this mechanism to be present in all nickel-rich cathodes and so these findings provide valuable insights into how to design future materials to limit this degradation process. 

Another study demonstrated the potential of newly discovered additives to cathode materials which markedly improve lithium-ion battery performance (Diaz-Lopez M et al. Adv. Energy Mat. 2020)¹⁶. One nanocomposite (Li2O:Li2/3−xMn1/3O5/6) showed great potential in counteracting the common drop in capacity of lithium-ion batteries.  French researchers used Diamond’s X-ray Pair Distribution Function (XPDF) beamline (I15-1) to produce high-quality, high-speed data on the local structure and performance of this new material. These nanocomposites can be produced easily and at low cost and show potential compatibility with industrial battery manufacturing processes so could represent a significant step forward in improving the performance of lithium-ion batteries. 

Several recent studies demonstrate the progress being made in improving the efficiency of solar cells.  A team from the University of Cambridge and a Swiss research facility (Tennyson EM et al. ACS Energy Lett 2021)¹⁷ used nanobeam X-ray Fluorescence data from beamline I14 to study the combination of crystalline silicon and halide perovskite, which is a promising new candidate for the next generation of photovoltaic cells. The research showed how the micro- and nanoscale structures affect device performance and will help to optimise the design and operation of newer solar cells. 

Another study focused on the use of lead halide perovskite solar cells which, despite high efficiency have often been found to have poor long-term stability. A Swedish team (Hultqvist A et al. ACS Appl Energy Mater 2021)¹⁸ studied the material in combination with a tin oxide (SnOx) film in order to understand and solve these stability issues and maintain performance. Soft and Hard X-ray Photoelectron Spectroscopy (SOXPES and HAXPES) was  carried out on Diamond’s Atomic and Electronic Structures of Surfaces and Interfaces beamline (I09) to analyse the chemistry of the perovskite/SnOx in order to optimise solar cell structure and performance. The study clearly showed that any detrimental effects can be avoided by controlling the interfacial design between the two materials. 

Two important studies carried out on beamline I22 by a research group from the University of Sheffield have corrected current thinking on the design and function of lead halide perovskite solar cells.  The first (Alanazi T et al. RSC Advances 2020)¹⁹ used SAXS to show that the addition of potassium iodide to the solar cell materials can reduce their operational stability; a result not identified in previous studies. The second (Game O et al. J Mat Chem A 2020)²⁰ examined the current suggestion that solvent vapour annealing is a beneficial technique to improve performance lead halide perovskite films. This common post-processing technique, which increases the grain size of the films, has been previously reckoned to lead to enhanced stability, but the research team used several microstructural characterisation techniques including SAXS to show the opposite.  These well-researched findings will aid ongoing development of high-performance solar cells. 

Research groups from around the world are also studying a range of materials in the effort to improve the power conversion efficiency and cost-effectiveness of perovskite solar cells. One effective strategy has been the rational design of electron transport layers of different semiconductors which are able to transport photogenerated electrons efficiently and protect the perovskite layers from moisture in the air. Semiconductors such as zinc oxide and tin oxide have been widely used in applications for metal halide perovskite solar cells. A recent Chinese study (Zhao R et al. Cell Reports Physical Science 2021)²¹ used small molecule single crystal diffraction on beamline I19 to demonstrate the effectiveness of a new composite electron transport layer material comprising zinc oxide nanocrystals with tin oxide nanoparticles. The new material improved the photovoltaic performance of the solar cells and provides another highly promising approach to improve the performance of metal halide perovskite solar cells. 

Organic solar cells (or organic photovoltaics) are carbon-based organic molecules which can convert energy from the sun into electricity. They are an emerging solar cell technology and have great potential to provide inexpensive energy. Research groups are currently trying to optimise the efficiency and longevity of these cells.  A team from the University of Oxford and Ain Shams University, Cairo (Abdelaal M et al. Materials 2021)²² used Diamond’s Surface & Interface X-ray Diffraction beamline (I07) to examine the microstructures of these cells. This research adds to the growing body of evidence demonstrating the potential of this exciting and sustainable method of energy production. 

This small sample of the pioneering studies that have taken place at Diamond over the past two years demonstrate the power of international collaboration in tackling some of the greatest global environmental challenges.  Diamond is also used by a number of commercial companies working on environmental issues – this selection of case studies demonstrates the breadth of industrial research in this area. Diamond Light Source is proud to play a significant part in both academic and industrial research that will provide sustainable solutions for the next generation.