Improving In-Situ Sodium Metal Plating on Copper Foil Through Optimization of Mechanical Pressure: Towards High-Performance Anode-Free Sodium Ion Batteries

Herein we report key developments on the scale-up of sodium ion anode free batteries through investigation of the effects of applied external pressure cell performance. Sodium ion anode free puts extra emphasis on high plating and stripping efficiency of sodium metal at the anode surface, due to the lack of an excess of the transporting ion. We demonstrate excellent Na||Cu half-cell results in coin cell configuration, and the scalability of the anode-free concept is further demonstrated, by plating and stripping of sodium metal on copper foils 10-fold larger (>10 cm 2) than in other studies in coin cells (∼1 cm2). It is discovered that pressure is paramount in establishing dendrite free sodium deposition at this scale through investigating the half-cell cycling at 56–743 kPa. Achieving a low hysteresis in these large-area cells is found to only require moderate pressures (∼185 kPa). However, achieving a high cycle life required increasing the pressure to 743 kPa. It is only at these high pressures that non-dendritic sodium deposition is demonstrated due to a homogeneous plating distribution enabled by proper contact between electrodes, as confirmed by impedance measurements and optical imaging of the deposited sodium

Exploring electrochemical deposition in aqueous and non-aqueous solvents using boron doped diamond electrodes

In this thesis, we use boron doped diamond (BDD) because of its unique properties such as: a high thermal conductivity, a good resistance to chemical and electrochemical attack, a very large potential window, and low background currents to investigate electrochemical deposition of the platinum group metals. We first explore the effects of deposition potential and time, in tandem with temperature control, on the morphology of Pt nanostructures created. In this way, we managed to make porous Pt nanoparticles (NPs) via a one-step deposition. We then further use electrochemistry as a diagnostic and analytical technique for characterisation of their electrocatalytic properties, using Pt NPs for studying methanol oxidation for energy conversion applications. Having realised the power of the transmission electron microscope (TEM) as an analytical and a quantitative tool. We made thin BDD (few nm thickness), to provide an electrode, which is electron transparent. Using this dual function BDD in combination with complimentary high-resolution electron microscopy techniques, it was possible to investigate the nucleation and growth of Au at the atomic level. By taking time snapshots, we can provide information about the mechanisms of early stage phase formation and the transition of amorphous nanostructures to crystalline NPs. Finally, we carry out spectroscopic, analytical and electrochemical studies to understand ion-ion, ion-solvent and solvent-solvent interactions, which then aid the utilisation of electrodeposition for the recovery of Pd from industrial-like solutions. We show that the addition of water to acetonitrile switches on the Pd electrodeposition from its Pd-acetate compound. Moreover, we provide proof of concept measurements for the electrochemical recovery of Pd from an organic synthesis solution, without impacting the organic molecules or the active pharmaceutical ingredients. In general, BDD holds a great avenue for nucleation and growth studies, provides features that allow controlling the metal electrodeposition and can be used to make specific nanostructures and catalysers

Controlling palladium morphology in electrodeposition from nanoparticles to dendrites via the use of mixed solvents

By changing the mole fraction of water (χwater) in the solvent acetonitrile (MeCN), we report a simple procedure to control nanostructure morphology during electrodeposition. We focus on the electrodeposition of palladium (Pd) on electron beam transparent boron-doped diamond (BDD) electrodes. Three solutions are employed, MeCN rich (90% v/v MeCN, χwater = 0.246), equal volumes (50% v/v MeCN, χwater = 0.743) and water rich (10% v/v MeCN, χwater = 0.963), with electrodeposition carried out under a constant, and high overpotential (−1.0 V), for fixed time periods (50, 150 and 300 s). Scanning transmission electron microscopy (STEM) reveals that in MeCN rich solution, Pd atoms, amorphous atom clusters and (majority) nanoparticles (NPs) result. As water content is increased, NPs are again evident but also elongated and defected nanostructures which grow in prominence with time. In the water rich environment, NPs and branched, concave and star-like Pd nanostructures are now seen, which with time translate to aggregated porous structures and ultimately dendrites. We attribute these observations to the role MeCN adsorption on Pd surfaces plays in retarding metal nucleation and growth

Novel Urinary Biomarkers and Chronic Kidney Disease After Coronary Angiography: A Prospective Case-Controlled Study

BACKGROUND: Novel urinary biomarkers may have potential for early detection of acute kidney injury. AIM: The aim of the study was to test two urinary biomarkers: Kidney injury molecule-1(KIM-1) and liver-type fatty acid binding protein (L-FABP) as markers of kidney injury following coronary angiography. METHODS: This is a prospective non-randomized controlled trial, performed in two large teaching hospitals. Patients were recruited from the catheter lab or form nephrology outpatient clinics. In group (A), 100 patients with AKI on top of CKD after coronary angiography and Group B: Thirty-one patients with stable CKD as a control. KIM-1 and L-FABP were measured at base line and after 3 months. RESULTS: In group (A), 100 patients who had acute on top of CKD after coronary angiography, stage progression occurred in 15 patients in group (A) compared to two patients in group (B) (p = 0.28). The median change in eGFR after 3 months was not statistically significant between both groups (p = 0.8). Median baseline urinary liver-type fatty acid binding protein was higher in Group A compared to Group B (3.7 μg/g vs. 1.82μg/g). The change in L-FABP from baseline to 3 months was significant between both groups (p < 0.001). The median urinary concentrations of KIM-1 and L-FABP were higher at the end of the follow-up compared to base line values in both groups, (p < 0.000). CONCLUSION: Urinary L-FABP correlates with kidney function decline in patients with acute on top of CKD after coronary angiography. Urinary levels of KIM-1 and L-FABP at 3 months increase significantly compared to baseline in patients with progressive CKD

Atomic-scale investigation of the reversible α- to ω-phase lithium ion charge – discharge characteristics of electrodeposited vanadium pentoxide nanobelts

Using an electrochemical potential pulse methodology in a mixed solvent system, electrochemical deposition of amorphous vanadium pentoxide (V2O5) nanobelts is possible. Crystallisation of the material is achieved using in air annealing with the temperature of crystallisation identified using in situ heating transmission electron microscopy (TEM). The resulting α-phase V2O5 nanobelts have typical thicknesses of 10–20 nm, widths and lengths in the range 5–37 nm (mean 9 nm) and 15–221 nm (mean 134 nm), respectively. One-cycle reversibility studies for lithium intercalation (discharge) and de-intercalation (charge) reveal a maximum specific capacity associated with three lithium ions incorporated per unit cell, indicative of ω-Li3V2O5 formation. Aberration corrected scanning TEM confirm the formation of ω-Li3V2O5 across the entirety of a nanobelt during discharge and also the reversible formation of the α-V2O5 phase upon full charge. Preliminary second cycle studies reveal reformation of the ω-Li3V2O5, accompanied with a morphological change in the nanobelt dimensions. Achieving α-V2O5 to ω-Li3V2O5 to α-V2O5 reversibility is extremely challenging given the large structural rearrangements required. This phenomenon has only been seen before in a very limited number of studies, mostly employing nanosized V2O5 materials and never before with electrodeposited material

Electron beam transparent boron doped diamond electrodes for combined electrochemistry─transmission electron microscopy

The majority of carbon based transmission electron microscopy (TEM) platforms (grids) have a significant sp2 carbon component. Here, we report a top down fabrication technique for producing freestanding, robust, electron beam transparent and conductive sp3 carbon substrates from boron doped diamond (BDD) using an ion milling/polishing process. X-ray photoelectron spectroscopy and electrochemical measurements reveal the sp3 carbon character and advantageous electrochemical properties of a BDD electrode are retained during the milling process. TEM diffraction studies show a dominant (110) crystallographic orientation. Compared with conventional carbon TEM films on metal supports, the BDD-TEM electrodes offer superior thermal, mechanical and electrochemical stability properties. For the latter, no carbon loss is observed over a wide electrochemical potential range (up to 1.80 V vs RHE) under prolonged testing times (5 h) in acid (comparable with accelerated stress testing protocols). This result also highlights the use of BDD as a corrosion free electrocatalyst TEM support for fundamental studies, and in practical energy conversion applications. High magnification TEM imaging demonstrates resolution of isolated, single atoms on the BDD-TEM electrode during electrodeposition, due to the low background electron scattering of the BDD surface. Given the high thermal conductivity and stability of the BDD-TEM electrodes, in situ monitoring of thermally induced morphological changes is also possible, shown here for the thermally induced crystallization of amorphous electrodeposited manganese oxide to the electrochemically active γ-phase

Mortality and pulmonary complications in patients undergoing surgery with perioperative SARS-CoV-2 infection: an international cohort study

Background: The impact of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) on postoperative recovery needs to be understood to inform clinical decision making during and after the COVID-19 pandemic. This study reports 30-day mortality and pulmonary complication rates in patients with perioperative SARS-CoV-2 infection. Methods: This international, multicentre, cohort study at 235 hospitals in 24 countries included all patients undergoing surgery who had SARS-CoV-2 infection confirmed within 7 days before or 30 days after surgery. The primary outcome measure was 30-day postoperative mortality and was assessed in all enrolled patients. The main secondary outcome measure was pulmonary complications, defined as pneumonia, acute respiratory distress syndrome, or unexpected postoperative ventilation. Findings: This analysis includes 1128 patients who had surgery between Jan 1 and March 31, 2020, of whom 835 (74·0%) had emergency surgery and 280 (24·8%) had elective surgery. SARS-CoV-2 infection was confirmed preoperatively in 294 (26·1%) patients. 30-day mortality was 23·8% (268 of 1128). Pulmonary complications occurred in 577 (51·2%) of 1128 patients; 30-day mortality in these patients was 38·0% (219 of 577), accounting for 81·7% (219 of 268) of all deaths. In adjusted analyses, 30-day mortality was associated with male sex (odds ratio 1·75 [95% CI 1·28–2·40], p\textless0·0001), age 70 years or older versus younger than 70 years (2·30 [1·65–3·22], p\textless0·0001), American Society of Anesthesiologists grades 3–5 versus grades 1–2 (2·35 [1·57–3·53], p\textless0·0001), malignant versus benign or obstetric diagnosis (1·55 [1·01–2·39], p=0·046), emergency versus elective surgery (1·67 [1·06–2·63], p=0·026), and major versus minor surgery (1·52 [1·01–2·31], p=0·047). Interpretation: Postoperative pulmonary complications occur in half of patients with perioperative SARS-CoV-2 infection and are associated with high mortality. Thresholds for surgery during the COVID-19 pandemic should be higher than during normal practice, particularly in men aged 70 years and older. Consideration should be given for postponing non-urgent procedures and promoting non-operative treatment to delay or avoid the need for surgery. Funding: National Institute for Health Research (NIHR), Association of Coloproctology of Great Britain and Ireland, Bowel and Cancer Research, Bowel Disease Research Foundation, Association of Upper Gastrointestinal Surgeons, British Association of Surgical Oncology, British Gynaecological Cancer Society, European Society of Coloproctology, NIHR Academy, Sarcoma UK, Vascular Society for Great Britain and Ireland, and Yorkshire Cancer Research

Die turbulente Taylor-Couette-Strömung mit sehr weitem Spalt : experimentelle Untersuchung

Die Taylor-Couette-Strömung (TC), die Strömung zwischen zwei konzentrischen, unabhängig voneinander rotierenden Zylindern, wird als perfektes Modell zur Untersuchung von Scherströmungen über konkaven Oberflächen verwendet und ist eines der paradigmatischen Systeme der Fluidphysik. In dieser Arbeit wird eine experimentelle Untersuchung der turbulenten TC-Strömung in einer sehr breiten Spaltgeometrie mit einem Radiusverhältnis = 0,1 durchgeführt. Das physikalische und dynamische Verhalten der Strömung wird in einer Geometrie untersucht, die vor der vorliegenden Studie kaum untersucht wurde, was diese Studie einzigartig macht. Ziel der Studie ist es, die Auswirkungen der Krümmung auf die TC-Strömung zu verstehen, insbesondere in Fällen, in denen die Umfangslänge des inneren Zylinders kleiner ist als die Spaltbreite. Die Strömung wird in den verschiedenen Rotationsregimen untersucht: gegenläufige, mitläufige und reine Innenzylinder-Rotationsregime bis zu Scher-Reynoldszahlen Re_s≤ 150000. Das Strömungsfeld wurde mit Hilfe von Visualisierungstechniken qualitativ untersucht. Bei der Untersuchung der verschiedenen Strömungsparameter zeigen sich bekannte kohärente TC-Strömungsmuster sowie neu beobachtete Muster, von denen wir annehmen, dass sie nur bei TC-Strömungen mit sehr großem Spalt existieren. Für eine detailliertere quantitative Untersuchung wurde eine zeitaufgelöste Messung des Geschwindigkeitsfeldes mit der Hochgeschwindigkeits-Partikel-Image-Velocimetry-Technik durch die Endplatte des Systems durchgeführt. Die radialen und azimutalen Geschwindigkeitskomponenten in der horizontalen 2D-Ebene werden an verschiedenen axialen Positionen gemessen, um die axiale Varianz der Strömung zu erfassen. Das aufgezeichnete Strömungsfeld wird verwendet, um den Drehimpulstransport in Form der Quasi-Nusselt-Zahl (Nu_ω) zu berechnen. Die Ergebnisse zeigen ein Maximum der Nu_ω für niedrige gegenläufige Raten von -0,011 ≤ μ_max ≤ -0,0077, was mit großräumigen Strukturen verbunden ist, die den gesamten Spalt überspannen. Darüber hinaus nimmt Nu_ω für Gegenrotationsraten, die höher als μ_max sind, ab, bis es einen Minimalwert erreicht, und steigt dann für höhere Gegenrotationsfälle tendenziell wieder an. Das Raum-Zeit-Verhalten des turbulenten Strömungsfeldes für die Fälle mit hoher Gegenrotation zeigt die Existenz neu beobachteter Muster neben der äußeren Zylinderwand, die sich nach innen ausbreiten, den Drehimpulstransport verstärken und zu einem zweiten Maximum im Transport für höhere Gegenrotationsraten führen. Das Raum-Zeit-Verhalten des turbulenten Strömungsfeldes für die Fälle mit hoher Gegenrotation zeigt die Existenz von neu beobachteten Mustern neben der äußeren Zylinderwand, die sich nach innen ausbreiten, den Drehimpulstransport verstärken und zu einem zweiten Maximum des Transports für höhere Gegenrotationsraten führen. Für den rein rotierenden inneren Zylinder skaliert der Impulstransport.The Taylor-Couette (TC) flow, the flow confined between two concentric independently rotating cylinders, is used as a perfect model to investigate shear flow over concave surfaces and one of the paradigmatic systems of the physics of fluids. In this thesis, an experimental investigation of the turbulent TC flow in a very wide gap geometry with a radius ratio = 0.1 is performed. The physical and dynamic behavior of the flow is studied in a geometry that has rarely been investigated before the current study, which makes this study unique. The study aims to understand the effect of curvature on the TC flow, particularly in cases where the circumferential length of the inner cylinder is smaller than the gap width. The flow is studied in the different rotation regimes: counter-rotating, co-rotating, and purely inner cylinder rotating regimes up to shear Reynolds numbers Re_s≤ 150000. The flow field has been qualitatively studied using visualization techniques. By probing the different flow parameters, familiar coherent TC flow patterns appear, in addition to newly observed patterns we assume only exist for very wide gap TC flows. For a more detailed quantitative study, a time-resolved velocity field measurement has been conducted using the High-speed Particle Image Velocimetry technique through the system end plate. The radial and azimuthal velocity components in the 2D horizontal plane are measured at different axial positions, in order to scan the axial variance of the flow. The recorded flow field is used to compute the angular momentum transport in terms of the quasi-Nusselt number (Nu_ω). The results show a maximum of Nu_ω for low counter-rotating rates of −0.011 ≤ μ_max ≤ −0.0077, which is associated with large-scale structures that span the entire gap. Moreover, the Nu_ω decreases for counter-rotation rates higher than μ_max until it reaches a minimum value and then tends to increase again for higher counter-rotation cases. The space-time behavior of the turbulent flow field for the high counter-rotating cases shows the existence of newly observed patterns next to the outer cylinder wall that propagates inward, enhancing the angular momentum transport and resulting in a second maximum in transport for higher counter-rotating rates. For the pure rotating inner cylinder, the momentum transport scaling with the shear rate Nu_ω ∼ Re_s^α has been studied, and it shows a transition in scaling to = −0.76 for all flows with Re_(s )≥ 25000. This new scaling reveals the transition of the flow from the classical turbulent regime to the ultimate one, where this transition is accompanied by a clear change in the flow behavior. Moreover, the flow in the co-rotating regime and particularly in the centrifugal stable regime ( > +0.01) is investigated. The Velocity measurements show the presence of disturbed flow near the inner cylinder, where the measured velocity profiles showed a clear deviation from those predicted by laminar flow for flows up to = +0.04

Controlling Pd Morphology in Electrodeposition from Nanoparticles to Dendrites via the use of Mixed Solvents

By changing the mole fraction of water (cwater) in the solvent acetonitrile (MeCN), we report a simple procedure to control nanostructure morphology during electrodeposition. We focus on the electrodeposition of palladium (Pd) on electron beam transparent boron-doped diamond (BDD) electrodes. Three solutions are employed MeCN rich (90% v/v MeCN, cwater = 0.246), equal volumes (50% v/v MeCN, cwater = 0.743) and water rich (10% v/v MeCN, cwater = 0.963) with electrodeposition carried out under diffusion-controlled conditions for fixed time periods (50, 150 and 300 s). Scanning transmission electron microscopy (STEM) reveals that in MeCN rich solution, Pd atoms, amorphous atom clusters and (majority) nanoparticles (NPs) result. As water content is increased, NPs are again evident but also elongated and defected nanostructures which grow in prominence with time. In the water rich environment, NPs and branched, concave and star-like Pd nanostructures are now seen, which with time translate to aggregated porous structures and ultimately dendrites. We attribute these observations to the role MeCN adsorption on Pd surfaces plays in retarding metal nucleation and growth.</p

Switching on palladium catalyst electrochemical removal from a palladium acetate–acetonitrile system via trace water addition

Palladium acetate (Pd-acetate) is a common catalyst used in a wide array of organic synthetic reactions in non-aqueous solvents. Due to its high cost and associated toxicity/contamination issues in reaction mixtures, Pd removal and recovery is essential. Here we explore the use of electrodeposition as a means to remove Pd from an acetonitrile (MeCN) based Suzuki cross coupling reaction solution, by plating metallic Pd onto the surface of an electrode (boron doped diamond). We show the importance of adding tolerable volumes of water to the reaction mixture in order to facilitate the electrodeposition process. In MeCN, strong coordination bonds exist between the Pd cation and acetate groups and electrodeposition is not possible. By adding water in controlled quantities we show using spectroscopic, electrochemical and microscopic techniques that acetate ligands are released from Pd co-ordination and first replaced by MeCN molecules, enabling electrodeposition. As the water content increases, the MeCN co-ordinating molecules are replaced by water, due to the favourable water–MeCN interactions overcoming those of Pd cation–MeCN, also promoting electrodeposition. We show that sufficient perturbation of the Pd-acetate structure to enable electrodeposition is possible in MeCN solutions containing as little as 5% water (v/v). We demonstrate 99.4% removal of Pd, as metallic Pd plated onto the electrode surface, from a Suzuki reaction solution, using electrochemical methods