Reversible Structural Changes Research Articles

Topotactic Electrochromism for Efficient Coloration Applications

AbstractTopotactic transitions, that is, reversible crystal structure changes due to controllable stoichiometry of material, offer substantial potential to control a wide variety of functionality in transition metal oxides, especially in systems with high ionic mobility and correlated electrons. Here the authors report on topotactic electrochromism with prominent coloration efficiency in SrCo0.66Fe0.34O3−δ associated with changes of electrical conductivity and electronic structure of the material. Changes in electron correlation lead to significant coloration and light absorption, which provides a general approach for utilizing topotactic transitions in electrochromic applications.

Chiral Cellulose Nanocrystal Humidity-Responsive Iridescent Films with Glucan for Tuned Iridescence and Reinforced Mechanics.

The fabrication of biomimetic photonic materials with environmental stimuli-responsive functions from entirely biobased materials is becoming increasingly challenging with the growing demand for biodegradable materials. Herein, the effect of glucan with different molecular weights on the mechanical performance and tunable structural color of iridescent CNC composite films was investigated. The existence of glucan did not influence the self-assembly performance of CNCs, but rather led to an improvement in the mechanical performance, enabling cholesteric CNC composite films with an adjustable structural color. Simultaneously, the iridescent films showed a conspicuous redshift and enlarged initial pitch without obstruction of the chiral structure. In response to environmental humidity, the structural colors of the iridescent composite films can be changed by regulating their chiral nematic structure. In particular, the films demonstrate a reversible structural color change between blue and red at RH between 50 and 98%. The resulting biobased iridescent composite films have potential applications in decorative coating, optical and humidity sensing, and anticounterfeiting.

Electrochemistry of Thin Films with In Situ/Operando Grazing Incidence X-Ray Scattering: Bypassing Electrolyte Scattering for High Fidelity Time Resolved Studies.

Electroactive polymer thin films undergo repeated reversible structural change during operation in electrochemical applications. While synchrotron X-ray scattering is powerful for the characterization of stand-alone and ex situ organic thin films, in situ/operando structural characterization has been underutilized-in large part due to complications arising from supporting electrolyte scattering. This has greatly hampered the development of application relevant structure property relationships. Therefore, a new methodology for in situ/operando X-ray characterization that separates the incident and scattered X-ray beam path from the electrolyte is developed. As a proof of concept, the operando structural characterization of weakly-scattering, organic mixed conducting thin films in an aqueous electrolyte environment is demonstrated, accessing previously unexplored changes in the π-π peak and diffuse scatter, while capturing the solvent swollen thin film structure which is inaccessible in previous ex situ studies. These in situ/operando measurements improve the sensitivity to structural changes, capturing minute changes not possible ex situ, and have multimodal potential such as combined Raman measurements that also serve to validate the true in situ/operando conditions of the cell. Finally, new directions enabled by this in situ/operando cell design are examined and state of the art measurements are compared.

Thixotropy of magnetorheological gel composites: Experimental testing and modelling

Magnetorheological gel (MRG) is known as an aspiring controllable composite which exhibit rapid and reversible structural changes subjected to magnetic fields. Its rheological manifestation of the structural changes induced by both the shearing flow and the magnetic field is the varying in viscosity or shear stress. This effect is called thixotropy if the structural changes are reversible and time dependent. In this study, time dependent rheological properties were characterised by a proposed stepwise experiment which revealed the effects of shear rate, magnetic field, and resting time on the structural break-down and rebuilding in MRG. The results indicated up to 15% decrease in the shear stress of MRG under the constant shear rate of 6000 1/s within 5 s. 4 s and 30 s of resting allows approx. 50% and 98% recoveries of the reversible structural change, respectively. The application and intensifying of magnetic fields tend to increase thixotropic yield stress but decrease the fluctuation state. A simple model was formulated to capture the unique time dependent structural changes of MRG under constant shear flow and magnetic field; and, showed accurate predictions of the thixotropic responses of MRG under the magnetic fields, shear rates and resting time considered.

Detection of Catalytically Linked Conformational Changes in Wild-Type Class Ia Ribonucleotide Reductase Using Reaction-Induced FTIR Spectroscopy

The enzyme, ribonucleotide reductase (RNR), is essential for DNA synthesis in all cells. The class Ia Escherichia coli RNR consists of two dimeric subunits, α2 and β2, which form an active but unstable heterodimer of dimers, α2β2. The structure of the wild-type form of the enzyme has been challenging to study due to the instability of the catalytic complex. A long-range proton-coupled electron-transfer (PCET) pathway facilitates radical migration from the Y122 radical-diiron cofactor in the β subunit to an active site cysteine, C439, in the α subunit to initiate the RNR chemistry. The PCET reactions and active site chemistry are spectroscopically masked by a rate-limiting, conformational gate. Here, we present a reaction-induced Fourier transform infrared (RIFTIR) spectroscopic method to monitor the mechanism of the active, wild-type RNR α2β2 complex. This method is employed to obtain new information about conformational changes accompanying RNR catalysis, including the role of carboxylate interactions, deprotonation, and oxidation of active site cysteines, and a detailed description of reversible secondary structural changes. Labeling of tyrosine revealed a conformationally active tyrosine in the β subunit, assigned to Y356β, which is part of the intersubunit PCET pathway. New insights into the roles of the inhibitors, azidoUDP and dATP, and the sensitivity of RIFTIR spectroscopy to detect subtle conformational motions arising from protein allostery are also presented.

Calcination of Clay Raw Materials in a Fluidized Bed.

Clay raw materials are diverse in terms of their mineral composition, as well as the content of colouring oxides and their physical properties. Determining the suitability of raw materials for various purposes requires comprehensive studies on their properties, as well as their appropriate correction, which is possible through the use of appropriate modification techniques. One of the most commonly used technologies for the enrichment of clay raw materials is to subject them to high temperatures, which, depending on the temperature regime used in the technological process, may cause the decomposition and removal of some addditional components (e.g., carbonates), as well as the removal of water and dehydroxylation of clay minerals, reversible structural changes, and the complete and permanent reconstruction of the mineral phases. This paper presents a new application for fluidization technology in the calcination of clay raw materials. The results of the experiment show that the fluidization method is competitive compared to the technologies that have been used so far, as a result of, inter alia, the much shorter time period required to carry out the calcination process and, consequently, the much lower energy expenditure, the high efficiency of burning coal, and the lower CO2 emissions resulting from the mixing taking place in the reactor.

Regeneration of Active Surface Alloys during Cyclic Oxidation and Reduction: Oxidation of H2 on Pd/Ag(111).

The surface morphology and composition of a catalyst during excursions between oxidizing and reducing conditions can change substantially, especially in bimetallic alloys. Both thermodynamic and kinetic factors play a role in determining the properties of alloy surfaces where the active phase may be a metastable state. Previously, Ag oxide reduction was shown to be dramatically enhanced when Pd is on the surface; however, Pd is more stable when dissolved in Ag, raising the question as to whether a highly active Pd surface state will persist over multiple reaction cycles, a requirement for catalytic function. Experiments herein demonstrate that the enhanced chemical functionality due to the presence of Pd on the surface is retained, based on the enhanced rate of silver oxide reduction over multiple oxidation/reduction cycles for a Pd/Ag(111) model. Repeated oxidation and reduction promote PdAg alloying, and reversible structural and compositional changes are detected using X-ray photoelectron spectroscopy. This study establishes that metastable phases can persist in reactive processes on surfaces, indicating their potential in heterogeneous catalysis.

Kinetic Rejuvenation of Li-Rich Layered and Disordered-Rocksalt Li-Ion Battery Cathodes upon Oxygen Redox

Li-rich cathode materials (x>1 in LixTM2-xO2, TM=transition metal) with a layered structure or a disordered-rocksalt structure have received tremendous attention as advanced battery cathodes [1,2,3]. These materials can deliver substantially higher gravimetric capacity (>250 mAh/g) and energy density (>800 Wh/kg) compared to traditional materials (e.g., LiCoO2; ~170 mAh/g, 660 Wh/kg). Moreover, they improve the Li-ion batteries' sustainability by removing or greatly reducing scarce and environmentally unfriendly elements in their structure. In these materials, the theoretical TM-redox capacity is typically limited to ~140 mAh/g because of the limited amount of redox-active TMs in their crystal structure [1,2,3]. As a result, to achieve a very high capacity (> 250 mAh/g), O-redox must additionally take place in the materials, which occurs in local Li-rich environments (e.g., OLi4TM2, OLi5TM1) around oxygen where there are non-bonding O 2p orbitals [4]. In Li-rich materials containing multiple TMs, the local electroneutrality demands the TM-sites in the OLi4TM2 or OLi5TM1-unit to be occupied by high-valent TM-cations (e.g., Ti4+, Mn4+) instead of low-valent ones (e.g., Ni2+), which often results in medium-range-order (MRO) of cations in the Li-rich layered cathodes or short-range-order (SRO) in the Li-rich disordered-rocksalt cathodes [1,5]. For instance, this tendency leads to the rise of the Li2MnO3-like MRO in the layered Li- and Mn-rich cathodes, and because the non-bonding O 2p orbitals are primarily in the Li2MnO3-like domains, O-redox also takes place within the domains [1,4]. Unfortunately, the radical oxygen ion generated upon oxygen oxidation is highly mobile, and as the oxygen is covalently bonded with TMs, this increased O-mobility often accompanies TM-migration, triggering reversible or irreversible structural changes in the Li-rich materials [1]. This structural changes result in oxygen loss or unwanted phase transformation, which leads to voltage- and capacity-decay. Therefore, minimizing the structural rearrangement while using combined TM- and O-redox has been widely considered a holy grail to developing Li-rich cathodes with high capacity and stability. For instance, Bruce et al. showed that by changing the superstructure from the honeycomb to ribbon structure, one could suppress the Mn-migration upon O-redox in the layered Na-(Li, Mn)-O cathode to reduce voltage hysteresis [6]. Moreover, Li-rich disordered-rocksalt cathodes also experience structural damages upon O-oxidation; hence, its mitigation by various methods (e.g., fluorination) has been at the center of its research [3,7].In this presentation, we demonstrate that, in contrast to the prevailing opinion, the O-redox-assisted structural change can be highly beneficial to Li-rich cathodes' performance by substantially reducing the internal Li-transport resistance [8]. We synthesized highly-Li-rich Co-free layered cathodes, which possess the Li2MnO3-type medium-range-order (MRO). These materials' initial capacities are low; yet, they undergo a 'rejuvenation' (activation) upon extended cycling with substantially reduced hysteresis and increased capacity, which correlates with the MRO disruption and associated volume expansion initiated by O-redox-facilitating TM-migration. Moreover, we show that virtually the same process occurs for a disordered-rocksalt-type Li-rich cathode (Li1.2Ni1/3Ti1/3Mo2/15O2), suggesting the universality of this process.Furthermore, we use this knowledge to inform a molten-salt treatment to pre-disturb MRO, expand crystal volume before cycling, and endow a surface gradient composition for our Li-rich Co-free layered cathodes, such that the treated materials can achieve high capacity (>230 mAh/g) from the very first cycle with excellent rate capability (154 mAh/g at 2 A/g) and outstanding capacity/voltage-retention (~4 % capacity-loss; ~140 mV voltage-loss after 200 cycles at 100 mA/g; >210 mAh/g). From these results, we explain the mechanism and universality of the rejuvenation process in various charge-ordered oxides and propose guidelines for designing advanced Li-rich cathode materials with combined transition metal- and oxygen-redox activities. References M. Thackeray et al., J. Mater. Chem. 17, 3112–3125 (2007).N. Yabuuchi et al., PNAS 112, 7650–7655 (2014).J. Lee et al., Nature 556, 185–190 (2018).Seo et al., Nature Chem. 8, 692–697 (2016).H. Ji et al., Nat. Commun. 10, 592 (2019).R. House et al., Nature 577, 502–508 (2020).Z. Lun et al., Adv. Energy. Mater. 1802959 (2019).J. Lee et al., ACS Appl. Energy Mater. 3, 7931–7943 (2020).

Controlled Assembly of Plasmonic Nanoparticles: From Static to Dynamic Nanostructures.

The spatial arrangement of plasmonic nanoparticles can dramatically affect their interaction with electromagnetic waves, which offers an effective approach to systematically control their optical properties and manifest new phenomena. To this end, significant efforts were made to develop methodologies by which the assembly structure of metal nanoparticles can be controlled with high precision. Herein, recent advances in bottom-up chemical strategies toward the well-controlled assembly of plasmonic nanoparticles, including multicomponent and multifunctional systems are reviewed. Further, it is discussed how the progress in this area has paved the way toward the construction of smart dynamic nanostructures capable of on-demand, reversible structural changes that alter their properties in a predictable and reproducible manner. Finally, this review provides insight into the challenges, future directions, and perspectives in the field of controlled plasmonic assemblies.

Mutual regulation of polarization and magnetization in BFCNT/BFCO heterostructure via stress analysis of dipoles

The ability to mutually regulate polarization and magnetization, highly desirable for future multifunctional devices, remains elusive despite extensive investigations. In this work, a concept of mutual regulation of ferroelectric and ferromagnetic orders via stress analysis of dipoles was proposed and the idea was demonstrated in a 2-2 type multiferroic Bi6Fe1·6Co0·2Ni0·2Ti3O18/Bi2FeCrO6 heterostructure fabricated by a sol-gel technique followed with a rapid thermal proces. Both ferroelectricity, ferromagnetism and magnetoelectric coupling of the composite thin film were studied by macro- and microscale measurements. It demonstrated that a reversible change in domain structure does occur while exerting a stress on dipoles by different applied fields, wherein the (inverse)-piezoelectric effect, magnetostriction, Lorentz force, and Hall effect play an important role in deflection of dipoles and evolution of domains, and thus the regulation of polarization and magnetization, making it attractive for novel memories.

CHANGES IN THE STRUCTURAL ORGANIZATION OF THE SPLEEN UNDER THE INFLUENCE OF MONOSODIUM GLUTAMATE AND AFTER ITS ABOLITION

Актуальність. Глутамат натрію є однією з найпоширеніших харчових добавок в світі. В статті наведено та проаналізовано дані експериментального дослідження, яке проводено на 52 білих щурах самцях та самках репродуктивного віку.
 Мета дослідження – вивчити морфометричні, гістологічні та електронно-мікроскопічні зміни паренхіми селезінки щурів за умов впливу глутамату натрію та після його відміни.
 Методи. Мікроанатомію компонентів селезінки білих щурів за умов фізіологічної норми дослідили на 10 інтактних тваринах. Експериментальні тварини поділені на 3 групи. Статистичну обробку цифрових даних проводили за допомогою програмного забезпечення «Excel» та «STATISTICA» 6.0 з використанням параметричного методу.
 Результати. Через вісім тижнів дії глутамату натрію виявлено достовірне зменшення відносної площі білої пульпи в паренхімі селезінки білих щурів самців та самок, збільшення кількості вторинних лімфоїдних вузликів, зростання кількості моноцитів, макрофагів, плазматичних клітин та клітин мієлоїдного ряду, зростання частки ретикулярної сполучної тканини в складі селезінкових тяжів червоної пульпи. Еритроцити та тромбоцити заповнюють не лише просвіт пазух селезінки, але й накопичуються в пульпарних тяжах, велика кількість лімфоцитів на різних стадіях апоптозу. Венозні пазухи червоної пульпи повнокровні, їхні просвіти розширені та дещо деформовані. Навколо судин та венозних пазух наявні ознаки набряку. Збільшення кількості плазматичних клітин свідчить про пришвидшення проліферації активованих лімфоцитів, яке є ознакою iмуноіндукуючого ефекту. Через чотири тижні після відміни глутамату натрію гістологічна та електронно-мікроскопічна будова органа майже не відрізняється від попередньої групи тварин. Зростає повнокрів’я судин паренхіми селезінки, щільність клітин зменшується. Збільшується кількість апоптично змінених клітин.
 Підсумок. Через вісім тижнів після відміни глутамату натрію зворотніх змін у структурі паренхіми селезінки не виявлено. Отже, відміна введення глутамату натрію після його тривалого впливу не «покращує» морфометричних показників паренхіми селезінки щурів та не призводить до відновлення структурної організації органа.

Ion-Induced Volume Transition in Gels and Its Role in Biology.

Incremental changes in ionic composition, solvent quality, and temperature can lead to reversible and abrupt structural changes in many synthetic and biopolymer systems. In the biological milieu, this nonlinear response is believed to play an important functional role in various biological systems, including DNA condensation, cell secretion, water flow in xylem of plants, cell resting potential, and formation of membraneless organelles. While these systems are markedly different from one another, a physicochemical framework that treats them as polyelectrolytes, provides a means to interpret experimental results and make in silico predictions. This article summarizes experimental results made on ion-induced volume phase transition in a polyelectrolyte model gel (sodium polyacrylate) and observations on the above-mentioned biological systems indicating the existence of a steep response.

Exploring Reversible Thermochromic Behavior in a Rare Ni(II)-MOF System.

Thermochromic metal-organic frameworks (MOFs) are promising functional materials for a wide range of applications due to their ability to exhibit color variation under external temperature stimuli, yet the development of them with high cyclability and efficient regeneration processes remains challenging. Here, presented is a rare example of an ultrastable Ni(II)-MOF exhibiting an unprecedented reversible four-step color change between two complementary colors in a wide temperature range, which could be repeated for at least 500 cycles without losing crystallinity and thermochromic performance. Notably, the regeneration can be achieved within 1 min by simply letting the crystals cool naturally in the air, facilitated by the unique nature of the channels' inner surface. The reversible thermochromic behavior is owing to a series of reversible crystal structure changes with temperature, including the stepwise dehydration/rehydration process, and structural changes. This work facilitates the future development of more MOF-based reversible thermochromic materials with excellent performance and improved practical applicability.

Enhanced electrochemical performance of MnFe@NiFe Prussian blue analogue benefited from the inhibition of Mn ions dissolution for sodium-ion batteries

Sodium manganese hexacyanoferrate (PBM) is one of the most promising cathode materials for sodium-ion batteries due to its high theoretical capacity, high voltage, and low cost. However, its cycling performance is limited by serious Mn ions dissolution during Na+ insertion/extraction. In this work, a facile in situ ion-exchange strategy is developed to synthesize sodium manganese hexacyanoferrate coated by sodium nickel hexacyanoferrate (PBM@PBN). The as-prepared PBM@PBN showed superior cyclic stability and enhanced rate capability. PBM@PBN exhibited a high reversible capacity of 126.9 mAh g−1 (1 C), with a capacity retention of 74.3% after 800 cycles. ICP results proved that superior cyclic stability was attributed to the inhibition of Mn ions dissolution by PBN coating. Besides, PBM@PBN also exhibited enhanced rate capability, and it delivered a high capacity of 87.2 mAh g−1 at 10 C. Ex-situ XRD proved that the PBM@PBN undergoes a reversible structural change (monoclinic ↔ cubic/tetragonal) during the whole cycle. PBN coating inhibited the PBM from suffering serious Mn ions dissolution during Na+ insertion/extraction, thus ensured the framework stability of PBM during long-term cycling and contributed to the excellent electrochemical performance. The simple preparation of PBM@PBN makes it accessible for large-scale applications.

Front Cover: Solvent Effect on the Spin State of an Iron(II)‐Triazole Trimer (Eur. J. Inorg. Chem. 2/2021)

The Front Cover shows the molecular structure of an iron(II)-triazole trimer that undergoes a single-crystal to single-crystal transformation following its spin transition between low spin (LS) and high spin (HS) upon immersion in different solvents. Magnetic and spectroscopic changes are represented here as almond tree branches in bloom. The reversible structural changes responsible for this solvent-responsive behavior in the solid state were identified by comparison of the crystal structure after immersion in acetonitrile or in toluene. Image credits: Irene Sánchez-Molina, David Nieto and Andrea Moneo. More information can be found in the Full Paper by I. Sánchez-Molina, J. R. Galán-Mascarós and co-workers.

In situ observation of pressure modulated reversible structural changes in the graphitic domains of carbide-derived carbons

Carbons are important in a multitude of applications, and thus, the reversible control of carbon structures is of high interest. Here we report the reversible formation of graphitic structures with three distinct interlayer distances in case of two carbide-derived carbons (CDCs) loaded under hydrogen pressure observed with in situ neutron scattering methods. The formation of these graphitic structures determined with in situ neutron diffraction is brought forth by the confinement of H2 in the porous structure when the temperature, T, is increased from T = 20 K–50 K under H2 loading from 68 mbar to 10 bar. The confinement of the desorbing H2 causes the pressure to increase inside the CDC structure and this increase of pressure is the cause for the reversible formation of graphitic domains. The confinement of H2 at T = 50 K is possible due to the presence of ultramicropores and suitable curved carbon structures. The three distinct formed graphitic domains correspond to a highly pressurized, conventional highly ordered graphitic, and disoriented graphitic domains with possible H2/H intercalation. In situ quasi-elastic neutron scattering and gas adsorption methods are used to determine the H2 transport properties and interactions with the CDCs.

Multifunctional Platform Based on Electrospun Nanofibers and Plasmonic Hydrogel: A Smart Nanostructured Pillow for Near-Infrared Light-Driven Biomedical Applications.

Multifunctional nanomaterials with the ability to respond to near-infrared (NIR) light stimulation are vital for the development of highly efficient biomedical nanoplatforms with a polytherapeutic approach. Inspired by the mesoglea structure of jellyfish bells, a biomimetic multifunctional nanostructured pillow with fast photothermal responsiveness for NIR light-controlled on-demand drug delivery is developed. We fabricate a nanoplatform with several hierarchical levels designed to generate a series of controlled, rapid, and reversible cascade-like structural changes upon NIR light irradiation. The mechanical contraction of the nanostructured platform, resulting from the increase of temperature to 42 °C due to plasmonic hydrogel-light interaction, causes a rapid expulsion of water from the inner structure, passing through an electrospun membrane anchored onto the hydrogel core. The mutual effects of the rise in temperature and water flow stimulate the release of molecules from the nanofibers. To expand the potential applications of the biomimetic platform, the photothermal responsiveness to reach the typical temperature level for performing photothermal therapy (PTT) is designed. The on-demand drug model penetration into pig tissue demonstrates the efficiency of the nanostructured platform in the rapid and controlled release of molecules, while the high biocompatibility confirms the pillow potential for biomedical applications based on the NIR light-driven multitherapy strategy.

Time-Domain Thermoreflectance Study on Superlattice-like Phase Changing Chalcogenide Materials

Phase change memory (PCM) has been developed as one of the next generation memory candidates due to its high read/write speeds, high densities, and non-volatile characteristics. This memory uses the phase change of the chalcogenide materials by Joule heating. However, there is a problem of requesting high reset current, thereby increasing power consumption during melt-quench process for its amorphization. As a way to solve the high reset current, interfacial PCM (iPCM) was suggested. It is based on the metastable states formed in superlattice-like GeTe/Sb2Te3 stack of high quality. This PCM operates with a reversible structural change between high and low resistance states without melt-quench process. However, if the heating from electrode is too excessive during the iPCM operation process, unwanted melting can occur and iPCM characteristics can be lost. Therefore, it is necessary to study the thermal effects of superlattice-like phase change material and electrode in order to ensure stability in conventional PCM or iPCM operation.In this study, we conduct time-domain thermoreflectance study on the molecular-beam-epitaxially grown phase change materials; GeTe and Sb2Te3. Phase change layer was consisted of single or superlattice-like structure. TiN metal layer was used to see the thermal boundary resistance between the metal and phase change materials. Au metal layer was deposited as a photothermal transducer layer due to its stability and thermoreflectance coefficient value. Thermal conductivities of signle and superlattice-like thin films are compared to analyze the thermal effects. In addtion, heat conduction between the metallic TiN and phase change material of high quality is considered.

(Invited) Structural and Mechanistic Details on the Oxygen Evolution Reaction on Nife Layered Double Hydroxide and Ni(OH)2

The incorporation of Fe3+ ions in Ni(OH)2 is responsible for a dramatic oxygen evolution reaction (OER) activity enhancement.1 NiFe based (oxy)hydroxides are among the most active electrocatalysts for the OER in alkaline electrolytes.2 Their crystal structure, known as layered double hydroxide (LDH), is composed of layers of edge sharing metal oxygen octahedra that are intercalated with water molecules and charge balancing anions (Figure 1).3 In contrast, Fe-free Ni(OH)2 can be synthesized in the well defined brucite-like crystal structure, which does not have intercalated species and is indicated as β-M(OH)2. Oxidative deprotonation and possibly the electrocatalytic OER reaction lead to reversible structural changes that are only observable with in operando or in situ methods.1, 4 Several reports investigated the oxidized phases, but key aspects of the catalytically OER active site remain elusive and more investigations are necessary.In this contribution our results obtained using in operando wide angle X-ray scattering (WAXS) on crystalline NiFe LDH nanostructured catalysts and β-Ni(OH)2 catalysts will be presented.5 We identified the structure of the active catalyst state and observed that the lattice spacing under operating conditions changes reaching a similar value for both catalysts (Figure 1). Using a unique differential electrochemical mass spectrometry (DEMS) apparatus and isotope labelled experiments we further unravel mechanistic details on how the OER mechanism proceeds on these catalysts.References D. Friebel, M. W. Louie, M. Bajdich, K. E. Sanwald, Y. Cai, A. M. Wise, M. J. Cheng, D. Sokaras, T. C. Weng, R. Alonso-Mori, R. C. Davis, J. R. Bargar, J. K. Norskov, A. Nilsson and A. T. Bell, J Am Chem Soc, 2015, 137, 1305-1313. M. Gong, Y. G. Li, H. L. Wang, Y. Y. Liang, J. Z. Wu, J. G. Zhou, J. Wang, T. Regier, F. Wei and H. J. Dai, J Am Chem Soc, 2013, 135, 8452-8455. F. Dionigi and P. Strasser, Advanced Energy Materials, 2016, 6. M. Gorlin, J. F. de Araujo, H. Schmies, D. Bernsmeier, S. Dresp, M. Gliech, Z. Jusys, P. Chernev, R. Kraehnert, H. Dau and P. Strasser, J Am Chem Soc, 2017, 139, 2070-2082. F. Dionigi, Z. Zeng, I. Sinev, T. Merzdorf, S. Deshpande, M. B. Lopez, S. Kunze, I. Zegkinoglou, H. Sarodnik, D. X. Fan, A. Bergmann, J. Drnec, J. F. De Araujo, M. Gliech, D. Teschner, J. Greeley, B. Roldan Cuenya and P. Strasser, submitted 2019. Figure 1. Shift of the (003) diffraction peak associated to the interlayer distance for NiFe LDH catalysts between the resting state (black) and OER active state (red).5 3D structural model of the as prepared NiFe LDH. Figure 1

A high sensitivity variable temperature infrared spectroscopy investigation of kaolinite structure changes.

A new approach for thermal analysis based on variable temperature infrared spectroscopy is described and evaluated. Diffuse reflection optics are employed with a sample heating system that does not employ a sealed environmental chamber. Rather than using a sample cup, a thin layer of solid particles is loaded into a "button" sample holder. The new design minimizes spectral artifacts and provides enhanced optical throughput compared to other designs, but necessitates a more restrictive sample heating temperature range. Results obtained while monitoring solid-state temperature-dependent changes are used to assess the sensitivity of the method. Infrared spectrum changes associated with reversible and irreversible kaolinite structure changes are described and characterized. Subtle temperature-dependent sample changes are revealed by positive and negative difference spectrum residuals, which are obtained by subtracting infrared spectra obtained at different temperatures. Scan-to-scan infrared spectrum relative standard deviations at 30 and 150°C were less than 1.0%, which was slightly higher than the ambient temperature reproducibility.