Beamline for Fast Operando Spectroscopy (SWIFT)

SWIFT is a high flux spectroscopy beamline to be built on a mid-straight section as part as the Diamond-II programme. The beamline is optimized for the study of samples under operando conditions, with the added potential to investigate sample heterogeneities at the 20 µm scale.   

SWIFT’s combination of high flux and time and spatial resolution will offer new opportunities in a very broad spectrum of scientific areas, spanning from chemistry, energy, catalysis and earth sciences to the study of metals in tissues. SWIFT will be not only complementary to the present suite of beamlines of the Spectroscopy Group, but it will also cover the gap left by the closure of the I20-EDE. SWIFT’s enhanced technical capabilities will represent a step change to Diamond’s capability to support the XAS academic and industrial communities.  

Catalysis Battery Research  Earth, environment, cultural heritage & planetary sciences Biosciences

In all forms of catalysis (homogeneous and heterogeneous catalysis, biocatalysis and electrocatalysis), a major challenge is the identification of the working active sites and how these are affected by reaction conditions, reaction time and in some systems, how these are distributed within the reactor. In order to acquire the required understanding of these systems, rapidly obtained measurements are critical and spatial resolution enables an image of practical working systems to be obtained.   

SWIFT’s high data collection rates will allow the observation of transient species formed as a function of the changing environment. This has been hitherto, extremely challenging and, often, impractical.  

The combination of a small beam and high acquisition speeds offered by SWIFT will enable tracing the kinetics of fast reactions and the dependency on gas feed and position in the catalyst bed in heterogenous systems. This is the case for the CO2 activation in dry reforming and oxidative dehydrogenation reactions, important to de-fossilise the chemical industry without requiring large amounts of green hydrogen. Molybdenum carbide catalyst have been shown to facilitate these processes through fast (ms) allotrope interconversions and phase changes to more oxidic species. SWIFT will be especially relevant for studying these sorts of reactions, as laboratory studies have suggested a gradual oxidation front moving through the catalysis bed.   

XAS mapping will also allow operando profiling of emission control monolith catalysts, where measurements as a function of the depth of penetration of gases through the wash-coat embedded in the monolith wall (in the order of 100-200 mm) as well as along the channel are critical. Using SWIFT capabilities, the cross sections of the monolith wall as a function of the transient conditions will be obtained, providing an understanding of the active sites and their relationship with the activity of the system.   

SWIFT’s spatial and temporal resolution will enable experiments that will take full advantage of the development of microfluidics to enable the determination of the critical initial nucleation and growth mechanisms of nanoparticles (NPs), zeolites, MOFs or catalyst supports during reaction and synthesis, including the observation of possible short-lived intermediates.   

To probe more challenging catalytic mechanisms, modulation-excitation (ME) capabilities will be also available in SWIFT, allowing spectators species to be distinguished from the active catalytic centres. ME experiments have been performed recently to correlate changes in structure with selectivity and activity data as a function of a transient change in the environment. To date, the ME measurements have limited time resolution under fluorescence mode. ME data taken at ms time resolution is of importance in exhaust catalysis including Three Way Catalysts (TWCs) for gasoline engines and low temperature NOx adsorbers in diesel engines which operate using rapid changes in the gas atmosphere. Both systems typically contain low concentrations ≤1 wt% Platinum Group Metals (PGMs) supported on CeZrO2, wash-coated onto ceramic monoliths. SWIFT would allow ME experiments to be designed and applied to heterogeneous, homogeneous and bio-catalytic reactions taking advantage of the high flux and the beamline’s time resolution.   

SWIFT’s high time resolution will also enable the study of the degradation mechanisms in electrocatalysis. It has been observed that oxidation of Pt occurs during oxygen reduction in Proton Exchange Membrane (PEM) fuel cells as the result of start/stop cycling. In these cases, the steady state structures determined by conventional techniques are not representative of the conditions that occur during accelerated durability tests (ADT), when the potential is quickly switched between 0.6 and 1.2 V. SWIFT will enable XAS measurements within one ADT, providing valuable information about the oxidation state of platinum under non-steady state conditions.   

Operando XAS techniques are key to understand the complex transformations and degradation processes occurring in battery cycling, given the amorphous nature of some of the intermediates formed during insertion/extraction of ions.   

SWIFT will enable the investigation of dynamics in fast battery systems optimized for power density, where fast charging and discharging can make the study of fundamental processes governing ion diffusion challenging. The investigation of materials of interest to the transport industry such as LiFePO4 and niobium tungsten oxides will be possible.   

SWIFT’s ability to switch rapidly between different absorption edges will enable the study of multi-element cathode materials, such as high-entropy disordered rocksalts, during operando studies. Simultaneous XAS and powder XRD collection capabilities will be crucial to understand the charge compensation mechanism occurring in this family of battery materials. 

The high flux on SWIFT will also be critical to examine the nature and behaviour of low concentration dopants which improve the stability in batteries or cathode materials that experience a small proportion of cationic migration during cycling. For example, in layered cathodes containing small quantity of Fe3+ ions, these migrate from their original octahedral sites to tetrahedral sites upon cycling. Fast XAS mapping in fluorescence mode acquired on SWIFT will allow correlating the chemical speciation, spatial distribution and dynamics of these dopants.   

Spatially resolved rapid scanning on SWIFT will provide information on the chemical speciation of samples with resolution (20 µm) well matched to the needs of several disciplines in the natural sciences, allowing at the same time to explore with high efficiency larger sample areas than now possible on Diamond micro- and nano-focusing instruments. The spatial resolution offered by SWIFT will enable the combination of spectroscopy and imaging studies of dilute elements within large geological or palaeontological objects allows exploration of the evolution and biodiversity of life and key anatomical adaptations (for example the vertebrate skeleton), as well as informing mechanisms of preservation and identifying residual compounds and breakdown products of the original biochemistry. The small beam is also vital for the analysis of radioactive samples. This will give us the ability to measure the local coordination of actinides within nuclear waste simulants during heating (and cooling), or irradiated tritium breeder materials to observe changes as radiation-induced defects are annealed. In addition, SWIFT will enable challenging in situ and operando studies of transient inclusions and localised chemical species within furnaces, diamond anvil, multi anvil and deformation rigs.   

SWIFT will also enable the study of corrosion phenomena on ms timescales with chemical sensitivity, including the formation of inhibited interfaces and protective corrosion scales, as well as the local breakdown of passive films and coatings. In addition, the 20 µm beam size is well matched to the microstructure of many alloys.  

SWIFT ability to acquire full spectra in short timescales will help to mitigate beam-induced damage, currently one of the biggest hindrances e.g. in the heritage sciences.  The risk of photo-reduction or devolatilization on very rare and/or unique samples, such as museum palaeontological specimens, artifacts and paintings can prevent their investigation with X-rays: the ability to monitor sample changes on test specimens rapidly will ensure that accurate damage assessments can be undertaken, allowing to tune the acquisition strategy accordingly. This is not possible today on slow scanning beamlines.   

A key challenge for the study of the role of endogenous metals such as Cu and Zn in neurodegenerative diseases such as Parkinson’s or Alzheimer’s, and the importance of exogenous metals such as Cr and Ti in adverse responses to biomedical devices is the accurate characterisation of the full chemical variation within the sample. SWIFT’s wide-field XAS mapping utilising the available 20 μm spatial resolution will significantly enhance the current 2D XAS mapping studies. The ability to change working energy range will be essential for many ‘on-tissue’ biological measurements as multiple elements need to be studied on the same regions.  

Metallo-enzymes find applications in multi-billion-dollar international industries, ranging from the bulk use of cellulases in washing powders to specialist enzymes for organic synthesis.  XAS has proven to be an essential tool for the elucidation of the electronic and geometrical structure of these metallo-enzymes. For example, Ni K-edge XAS has unravelled how the nickel centre at the active site of Ni-Fe hydrogenase responds to the addition of H2 gas, discovering that the nickel changes its coordination geometry at different stages of the enzyme’s catalytic cycle. Similarly, lytic polysaccharide monooxygenase (LPMOs) enzymes, discovered in 2010, are Cu-containing oxygenases that find application in the production of cellulosic bioethanol. SWIFT will enable studies of these systems in real time, allowing the structural determination of reactive intermediates that cannot be isolated, but often hold the key to the enzymes operation. As in the previous case, the fast acquisition rates achieved by SWIFT will enable the study of this often photo-sensitive systems before X-ray damage occurs.