Effect of a Standardized Ginger Root Powder Regimen on Chemotherapy-Induced Nausea and Vomiting: A Multicenter, Double-Blind, Placebo-Controlled Randomized Trial.

BACKGROUND: There is substantial interest in the role of ginger as an adjuvant therapy for chemotherapy-induced nausea and vomiting (CINV). However, available evidence lacks robust methodology. OBJECTIVE: To assess the effect of adjuvant ginger compared with placebo on chemotherapy-induced nausea-related quality of life (QoL) and CINV-related outcomes. DESIGN: A parallel, double-blind, placebo-controlled randomized trial with 1:1 allocation was conducted. PARTICIPANTS/SETTING: One hundred three chemotherapy-naïve adults scheduled to receive moderately to highly emetogenic chemotherapy at two hospitals in Australia were enrolled and analyzed. INTERVENTION: Four standardized ginger capsules (totaling 84 mg/day active gingerols/shogaols), or placebo, were administered commencing the day of chemotherapy and continuing for 5 days for chemotherapy cycles 1 through 3. MAIN OUTCOME MEASURES: The primary outcome was chemotherapy-induced nausea-related QoL. Secondary outcomes were vomiting- and CINV-related QoL; anticipatory, acute, and delayed nausea and vomiting; fatigue; nutritional status; depression and anxiety; health-related QoL; and adverse events. STATISTICAL ANALYSES PERFORMED: Intention-to-treat analysis was performed. Mixed analysis of variance with repeated measures determined differences between groups. The null hypothesis was no difference between groups. After applying a Bonferroni multiple testing correction, evidence against the null hypothesis was considered at P= 0.003. RESULTS: One hundred three participants (ginger: n = 52; placebo: n = 51) were enrolled and analyzed. There was clinically relevant evidence against the null hypothesis, favoring ginger, in change scores for nausea-related QoL (F[df] = 9.34[1,101]; P = 0.003; partial η2 = 0.09), overall CINV-related QoL (F[df] = 12.26[1,101]; P < 0.001; partial η2 = 0.11), delayed nausea severity (F[df] = 9.46[1,101]; P = 0.003; partial η2 = 0.09), and fatigue (F[df] = 10.11[1,101]; P = 0.002; partial η2 = 0.09). There was a clinically meaningful lower incidence of delayed nausea and vomiting in the ginger group at Cycle 2 (53% vs 75%; P = 0.020 and 4% vs 27%; P = 0.001, respectively) and Cycle 3 (49% vs 79%; P = 0.002 and 2% vs 23%; P = 0.001, respectively). There was a clinically meaningful lower incidence of malnutrition in the ginger group at Cycle 3 (18% vs. 41%; P = 0.032) and in change scores for Patient-Generated Subjective Global Assessment (F[df)] = 4.32[1,100]; P = 0.040; partial η2 = 0.04). Change scores between groups favored ginger for vomiting-related QoL and number of vomiting episodes; however, findings were not clinically meaningful. There was no effect of ginger on anticipatory or acute CINV, health-related QoL, anxiety, or depression. No serious adverse events were reported. CONCLUSIONS: Ginger supplementation was a safe adjuvant to antiemetic medications for CINV that enhanced QoL during chemotherapy treatment. Future trials are needed to examine dose-dependent responses to verify optimal dosing regimens.

Universality of Hair as a Nucleant: Exploring the Effects of Surface Chemistry and Topography.

The ability to control crystal nucleation through the simple addition of a nucleating agent (nucleant) is desirable for a huge range of applications. However, effective nucleating agents are known for only a small number of systems, and many questions remain about the mechanisms by which they operate. Here, we explore the features that make an effective nucleant and demonstrate that the biological material hair-which naturally possesses a chemically and topographically complex surface structure-has excellent potential as an effective nucleating agent. Crystallization of poorly soluble compounds in the presence of hairs from a range of mammals shows that nucleation preferentially occurs at the cuticle step edges, while a novel microdroplet-based methodology was used to quantify the nucleating activities of different hairs. This showed that the activities of the hairs can be tuned over a wide range using chemical treatments. Analysis of the hair structure and composition using atomic force microscopy, scanning ion conductance microscopy, and X-ray photoelectron spectroscopy demonstrates that surface chemistry, surface topography, and surface charge all act in combination to create effective nucleation sites. This work therefore contributes to our understanding of heterogeneous nucleating agents and shows that surface topography as well as surface chemistry can be used in the design or selection of universal nucleating agents.

Multiscale Electrochemistry of Lithium Manganese Oxide (LiMn2O4): From Single Particles to Ensembles and Degrees of Electrolyte Wetting.

Scanning electrochemical cell microscopy (SECCM) facilitates single particle measurements of battery materials using voltammetry at fast scan rates (1 V s-1), providing detailed insight into intrinsic particle kinetics, otherwise obscured by matrix effects. Here, we elucidate the electrochemistry of lithium manganese oxide (LiMn2O4) particles, using a series of SECCM probes of graded size to determine the evolution of electrochemical characteristics from the single particle to ensemble level. Nanometer scale control over the SECCM meniscus cell position and height further allows the study of variable particle/substrate electrolyte wetting, including comparison of fully wetted particles (where contact is also made with the underlying glassy carbon substrate electrode) vs partly wetted particles. We find ensembles of LiMn2O4 particles show voltammograms with much larger peak separations than those of single particles. In addition, if the SECCM meniscus is brought into contact with the substrate electrode, such that the particle-support contact changes from dry to wet, a further dramatic increase in peak separation is observed. Finite element method modeling of the system reveals the importance of finite electronic conductivity of the particles, contact resistance, surface kinetics, particle size, and contact area with the electrode surface in determining the voltammetric waveshape at fast scan rates, while the responses are relatively insensitive to Li+ diffusion coefficients over a range of typical values. The simulation results explain the variability in voltammetric responses seen at the single particle level and reveal some of the key factors responsible for the evolution of the response, from ensemble, contact, and wetting perspectives. The variables and considerations explored herein are applicable to any single entity (nanoscale) electrochemical study involving low conductivity materials and should serve as a useful guide for further investigations of this type. Overall, this study highlights the potential of multiscale measurements, where wetting, electronic contact, and ionic contact can be varied independently, to inform the design of practical composite electrodes.

Role of Mass Transport in the Deposition, Growth, and Transformation of Calcium Carbonate on Surfaces at High Supersaturation.

We demonstrate how combined in-situ measurements and finite element method modeling can provide new insight into the relative contribution of mass transport to the growth of calcium carbonate on two model surfaces, glass and gold, under high-supersaturation conditions relevant to surface scaling. An impinging jet-radial flow system is used to create a high-supersaturated solution at the inlet of different cells: an optical microscope cell presenting a glass surface for deposition and quartz crystal microbalance (QCM) and in-situ IR spectroscopy cells, both presenting a gold surface. The approach described is quantitative due to the well-defined mass transport, and both time-lapse optical microscopy images and QCM data are analyzed to provide information on the growth kinetics of the calcite crystals. Initially, amorphous calcium carbonate (ACC), formed in solution, dominates the deposition process. At longer times, the growth of calcite is more significant and, on glass, is observed to consume ACC from the surface, leading to surface regions depleted of ACC developing around calcite microcrystals. On Au, the mass increase becomes linear with time in this region. Taken together, these microscopic and macroscopic measurements demonstrate that calcite growth has a significant component of mass transport control at high supersaturation. Finite element method (FEM) simulations of mass-transport-limited crystal growth support the strong mass transport contribution to the growth kinetics and further suggest that the observed growth must be sustained by more than just the Ca2+ and CO3 2- in solution, with dissolution/direct attachment of ACC and/or ion pairs also contributing to the growth process.

Critical Step Length as an Indicator of Surface Supersaturation during Crystal Growth from Solution.

The surface processes that control crystal growth from solution can be probed in real-time by in situ microscopy. However, when mass transport (partly) limits growth, the interfacial solution conditions are difficult to determine, precluding quantitative measurement. Here, we demonstrate the use of a thermodynamic feature of crystal surfaces-the critical step length-to convey the local supersaturation, allowing the surface-controlled kinetics to be obtained. Applying this method to atomic force microscopy measurements of calcite, which are shown to fall within the regime of mixed surface/transport control, unites calcite step velocities with the Kossel-Stranski model, resolves disparities between growth rates measured under different mass transport conditions, and reveals why the Gibbs-Thomson effect in calcite departs from classical theory. Our approach expands the scope of in situ microscopy by decoupling quantitative measurement from the influence of mass transport.

Hybrid scanning electrochemical cell microscopy-interference reflection microscopy (SECCM-IRM): tracking phase formation on surfaces in small volumes.

We describe the combination of scanning electrochemical cell microscopy (SECCM) and interference reflection microscopy (IRM) to produce a compelling technique for the study of interfacial processes and to track the SECCM meniscus status in real-time. SECCM allows reactions to be confined to well defined nm-to-µm-sized regions of a surface, and for experiments to be repeated quickly and easily at multiple locations. IRM is a highly surface-sensitive technique which reveals processes happening (very) close to a substrate with temporal and spatial resolution commensurate with typical electrochemical techniques. By using thin transparent conductive layers on glass as substrates, IRM can be coupled to SECCM, to allow real-time in situ optical monitoring of the SECCM meniscus and of processes that occur within it at the electrode/electrolyte interface. We first use the technique to assess the stability of the SECCM meniscus during voltammetry at an indium tin oxide (ITO) electrode at close to neutral pH, demonstrating that the meniscus contact area is rather stable over a large potential window and reproducible, varying by only ca. 5% over different SECCM approaches. At high cathodic potentials, subtle electrowetting is easily detected and quantified. We also look inside the meniscus to reveal surface changes at extreme cathodic potentials, assigned to the possible formation of indium nanoparticles. Finally, we examine the effect of meniscus size and driving potential on CaCO3 precipitation at the ITO electrode as a result of electrochemically-generated pH swings. We are able to track the number, spatial distribution and morphology of material with high spatiotemporal resolution and rationalise some of the observed deposition patterns with finite element method modelling of reactive-transport. Growth of solid phases on surfaces from solution is an important pathway to functional materials and SECCM-IRM provides a means for in situ or in operando visualisation and tracking of these processes with improved fidelity. We anticipate that this technique will be particularly powerful for the study of phase formation processes, especially as the high throughput nature of SECCM-IRM (where each spot is a separate experiment) will allow for the creation of large datasets, exploring a wide experimental parameter landscape.

Visualization of Ion Fluxes in Nanopipettes: Detection and Analysis of Electro-osmosis of the Second Kind.

Nanopipettes are finding increasing use as nano "test tubes", with reactions triggered through application of an electrochemical potential between electrodes in the nanopipette and a bathing solution (bath). Key to this application is an understanding of how the applied potential induces mixing of the reagents from the nanopipette and the bath. Here, we demonstrate a laser scanning confocal microscope (LSCM) approach to tracking the ingress of dye into a nanopipette (20-50 nm diameter end opening). We examine the case of dianionic fluorescein under alkaline conditions (pH 11) and large applied tip potentials (±10 V), with respect to the bath, and surprisingly find that dye ingress from the bath into the nanopipette is not observed under either sign of potential. Finite element method (FEM) simulations indicate this is due to the dominance of electro-osmosis in mass transport, with electro-osmotic flow in the conventional direction at +10 V and electro-osmosis of the second kind acting in the same direction at -10 V, caused by the formation of significant space charge in the center of the orifice. The results highlight the significant deviation in mass transport behavior that emerges at the nanoscale and the utility of the combined LSCM and FEM approach in deepening understanding, which in turn should promote new applications of nanopipettes.

Electrochemistry, ion adsorption and dynamics in the double layer: a study of NaCl(aq) on graphite.

Graphite and related sp2 carbons are ubiquitous electrode materials with particular promise for use in e.g., energy storage and desalination devices, but very little is known about the properties of the carbon-electrolyte double layer at technologically relevant concentrations. Here, the (electrified) graphite-NaCl(aq) interface was examined using constant chemical potential molecular dynamics (CµMD) simulations; this approach avoids ion depletion (due to surface adsorption) and maintains a constant concentration, electroneutral bulk solution beyond the surface. Specific Na+ adsorption at the graphite basal surface causes charging of the interface in the absence of an applied potential. At moderate bulk concentrations, this leads to accumulation of counter-ions in a diffuse layer to balance the effective surface charge, consistent with established models of the electrical double layer. Beyond ∼0.6 M, however, a combination of over-screening and ion crowding in the double layer results in alternating compact layers of charge density perpendicular to the interface. The transition to this regime is marked by an increasing double layer size and anomalous negative shifts to the potential of zero charge with incremental changes to the bulk concentration. Our observations are supported by changes to the position of the differential capacitance minimum measured by electrochemical impedance spectroscopy, and are explained in terms of the screening behaviour and asymmetric ion adsorption. Furthermore, a striking level of agreement between the differential capacitance from solution evaluated in simulations and measured in experiments allows us to critically assess electrochemical capacitance measurements which have previously been considered to report simply on the density of states of the graphite material at the potential of zero charge. Our work shows that the solution side of the double layer provides the more dominant contribution to the overall measured capacitance. Finally, ion crowding at the highest concentrations (beyond ∼5 M) leads to the formation of liquid-like NaCl clusters confined to highly non-ideal regions of the double layer, where ion diffusion is up to five times slower than in the bulk. The implications of changes to the speciation of ions on reactive events in the double layer are discussed.

Scanning Ion Conductance Microscopy: Surface Charge Effects on Electroosmotic Flow Delivery from a Nanopipette.

Scanning ion conductance microscopy (SICM) is a powerful and versatile technique that allows an increasingly wide range of interfacial properties and processes to be studied. SICM employs a nanopipette tip that contains electrolyte solution and a quasi-reference counter electrode (QRCE), to which a potential is applied with respect to a QRCE in a bathing solution, in which the tip is placed. The work herein considers the potential-controlled delivery of uncharged electroactive molecules (solute) from an SICM tip to a working electrode substrate to determine the effect of the substrate on electroosmotic flow (EOF). Specifically, the local delivery of hydroquinone from the tip to a carbon fiber ultramicroelectrode (CF UME) provides a means of quantifying the rate of mass transport from the nanopipette and mapping electroactivity via the CF UME current response for hydroquinone oxidation to benzoquinone. EOF, and therefore species delivery, has a particularly strong dependence on the charge of the substrate surface at close nanopipette-substrate surface separations, with implications for retaining neutral solute within the tip predelivery and for the delivery process itself, both controlled via the applied tip potential. Finite element method (FEM) simulations of mass transport and reactivity are used to explain the experimental observations and identify the nature of EOF, including unusual flow patterns under certain conditions. The combination of experimental results with FEM simulations provides new insights on mass transport in SICM that will enhance quantitative applications and enable new possibilities for the use of nanopipettes for local delivery.

Survival of advanced melanoma patients treated with immunotherapy and targeted therapy: A real-world study.

INTRODUCTION: We aimed to examine the survival outcomes plus patient and treatment characteristics of advanced melanoma patients treated with first-line immunotherapy (IT), targeted therapy (TT), and chemotherapy (CTH) and compare findings with information from pivotal trials for each therapy. MATERIALS AND METHODS: We retrospectively reviewed the use of systematic IT, TT and CTH therapies in melanoma patients in four Queensland public hospitals. We estimated median duration of overall survival (OS) and survival rates (6 months, 1, and 2 years) using Kaplan-Meier methods. We compared our findings to those of clinical trials. RESULTS: Five hundred three patients who met the inclusion criteria were divided into three groups based on the first-line treatment: IT 232; TT 157; and CTH 114. OS was 18 months with IT (95% CI 13, 22); 12 months with TT (95% CI 8, 15); and 5 months with CTH (95% CI 5, 6). The demographic characteristics, treatment protocols, and durations for IT and TT were generally consistent with trials but fewer patients in our study had subsequent therapy than in the trials. The OS in our study was slightly lower than the OS reported in trials. CONCLUSION: The OS of novel cancer therapy in the real world was lower than seen in trials but is expected given these are patients who have a poorer prognosis. A future study could investigate the impact of prognostic factors on survival in the longer term. This study provides evidence that we can use routinely collected real-world data to evaluate the effectiveness of checkpoint and kinase inhibitors in patients with advanced melanoma.

Microstructural origin of locally enhanced CO2 electroreduction activity on gold.

Understanding how the bulk structure of a material affects catalysis on its surface is critical to the development of actionable catalyst design principles. Bulk defects have been shown to affect electrocatalytic materials that are important for energy conversion systems, but the structural origins of these effects have not been fully elucidated. Here we use a combination of high-resolution scanning electrochemical cell microscopy and electron backscatter diffraction to visualize the potential-dependent electrocatalytic carbon dioxide [Formula: see text] electroreduction and hydrogen [Formula: see text] evolution activity on Au electrodes and probe the effects of bulk defects. Comparing colocated activity maps and videos to the underlying microstructure and lattice deformation supports a model in which CO2 electroreduction is selectively enhanced by surface-terminating dislocations, which can accumulate at grain boundaries and slip bands. Our results suggest that the deliberate introduction of dislocations into materials is a promising strategy for improving catalytic properties.

Research governance authorisation: the next frontier.

Objective There is much interest in examining the use of medicines and their real-world benefits and harms using routinely collected data sources such as patients' electronic medical records in hospitals in order to optimise use and health outcomes. This study aimed to describe the process and challenges involved in obtaining ethical approval and research governance authorisation for a research project that started on 7 December 2018 in Queensland and make recommendations for improving the process. Methods There were three aspects: (a) ethics approval; (b) governance - site-specific assessment (SSA); and (c) governance - Public Health Act (PHA) Application Assessment. Results The process to satisfy all requirements took more than 1 year (371 days); ethics took 16 days and PHA approval 16 days. The major hurdle was the SSA, which took 98-274 days across five sites. The main issues were opaqueness in processes and inconsistences in approach leading to considerable frustration. Discussion It is recommendeded that Research Governance Offices should be clear on the process and requirements. All Local Hospital Networks (LHN, Hospital and Health Services in Queensland) should develop and adopt a standardised low and negligible risk SSA approval process. Frustration of government officials and researchers led the National Health and Medical Research Council to streamline ethics approval processes, but the same cannot be said for the governance process. It is appreciated that LHN processes were developed for good and valid reasons, but the onerous and inconsistent application of these processes hinder timely and relevant research. It is time for action: follow the success of the ethics process to redesign governance. What is known about the topic? Researchers are interested in examining the use of medicines and their real-world benefits and harms using routinely collected data sources such as patients' electronic medical records in hospitals in order to optimise use and health outcomes. There are challenges in obtaining ethical approval and research governance authorisation for research projects. What does this paper add? We identified that the main hurdle was obtaining site-specific agreements across numerous hospital sites. What are the implications for practitioners? We recommend that Research Governance Offices should be clear on the process and requirements. All Local Hospital Networks (LHN, Hospital and Health Services in Queensland) should develop and adopt a standardised low and negligible risk SSA approval process. The ethics approval process has been streamlined in recent years so we need to follow this success to redesign governance.

Artificial Synapse: Spatiotemporal Heterogeneities in Dopamine Electrochemistry at a Carbon Fiber Ultramicroelectrode.

An artificial synapse is developed that mimics ultramicroelectrode (UME) amperometric detection of single cell exocytosis. It comprises the nanopipette of a scanning ion conductance microscope (SICM), which delivers rapid pulses of neurotransmitter (dopamine) locally and on demand at >1000 defined locations of a carbon fiber (CF) UME in each experiment. Analysis of the resulting UME current-space-time data reveals spatiotemporal heterogeneous electrode activity on the nanoscale and submillisecond time scale for dopamine electrooxidation at typical UME detection potentials. Through complementary surface charge mapping and finite element method (FEM) simulations, these previously unseen variations in electrochemical activity are related to heterogeneities in the surface chemistry of the CF UME.

Nanoscale kinetics of amorphous calcium carbonate precipitation in H2O and D2O.

Calcium carbonate (CaCO3) is one of the most well-studied and abundant natural materials on Earth. Crystallisation of CaCO3 is often observed to proceed via an amorphous calcium carbonate (ACC) phase, as a precursor to more stable crystalline polymorphs such as vaterite and calcite. Despite its importance, the kinetics of ACC formation have proved difficult to study, in part due to rapid precipitation at moderate supersaturations, and the instability of ACC with respect to all other polymorphs. However, ACC can be stabilised under confinement conditions, such as those provided by a nanopipette. This paper demonstrates electrochemical mixing of a Ca2+ salt (CaCl2) and a HCO3- salt (NaHCO3) in a nanopipette to repeatedly and reversibly precipitate nanoparticles of ACC under confined conditions, as confirmed by scanning transmission electron microscopy (STEM). Measuring the current as a function of applied potential across the end of the nanopipette and time provides millisecond-resolved measurements of the induction time for ACC precipitation. We demonstrate that under conditions of electrochemical mixing, ACC precipitation is extremely fast, and highly pH sensitive with an apparent third order dependence on CO32- concentration. Furthermore, the rate is very similar for the equivalent CO32- concentrations in D2O, suggesting that neither ion dehydration nor HCO3- deprotonation represent significant energetic barriers to the formation of ACC. Finite element method simulations of the electrochemical mixing process enable the supersaturation to be estimated for all conditions and accurately predict the location of precipitation.

Electrochemical Impedance Measurements in Scanning Ion Conductance Microscopy.

Electrochemical impedance spectroscopy (EIS) is a versatile tool for electrochemistry, particularly when applied locally to reveal the properties and dynamics of heterogeneous interfaces. A new method to generate local electrochemical impedance spectra is outlined, by applying a harmonic bias between a quasi-reference counter electrode (QRCE) placed in a nanopipet tip of a scanning ion conductance microscope (SICM) and a conductive (working electrode) substrate (two-electrode setup). The AC frequency can be tuned so that the magnitude of the impedance is sensitive to the tip-to-substrate distance, whereas the phase angle is broadly defined by the local capacitive response of the electrical double layer (EDL) of the working electrode. This development enables the surface topography and the local capacitance to be sensed reliably, and separately, in a single measurement. Further, self-referencing the probe impedance near the surface to that in the bulk solution allows the local capacitive response of the working electrode substrate in the overall AC signal to be determined, establishing a quantitative footing for the methodology. The spatial resolution of AC-SICM is an order of magnitude larger than the tip size (100 nm radius), for the studies herein, due to frequency dispersion. Comprehensive finite element method (FEM) modeling is undertaken to optimize the experimental conditions and minimize the experimental artifacts originating from the frequency dispersion phenomenon, and provides an avenue to explore the means by which the spatial resolution could be further improved.

Electric Field-Controlled Synthesis and Characterisation of Single Metal-Organic-Framework (MOF) Nanoparticles.

Achieving control over the size distribution of metal-organic-framework (MOF) nanoparticles is key to biomedical applications and seeding techniques. Electrochemical control over the nanoparticle synthesis of the MOF, HKUST-1, is achieved using a nanopipette injection method to locally mix Cu2+ salt precursor and benzene-1,3,5-tricarboxylate (BTC3- ) ligand reagents, to form MOF nanocrystals, and collect and characterise them on a TEM grid. In situ analysis of the size and translocation frequency of HKUST-1 nanoparticles is demonstrated, using the nanopipette to detect resistive pulses as nanoparticles form. Complementary modelling of mass transport in the electric field, enables particle size to be estimated and explains the feasibility of particular reaction conditions, including inhibitory effects of excess BTC3- . These new methods should be applicable to a variety of MOFs, and scaling up synthesis possible via arrays of nanoscale reaction centres, for example using nanopore membranes.

Bortezomib use and outcomes for the treatment of multiple myeloma.

BACKGROUND: The public subsidy in Australia of bortezomib (Velcade) for untreated non-transplant multiple myeloma patients was based on the VISTA trial. AIMS: To ascertain the health outcomes of bortezomib in 'real world' transplant-ineligible elderly patients, compared to trial data. METHODS: Patient and treatment data were extracted from an oncology information system, laboratory information system and medical chart audits for three Queensland public hospitals. RESULTS: We identified 74 patients; the median age was 75 years. Our cohort comprised 47% patients who were International Staging System stage III, 45% at stage II and 8% at stage I. Patients who had comorbidities, such as cardiac disease (41%), pulmonary disease (14%), diabetes (22%), peripheral neuropathy (14%) and other comorbidities (41%) at baseline were included. The common regimens prescribed were VMP, CVD and VD, and most patients (n = 73) received bortezomib on a once-weekly or twice-a-week basis. The overall response rate was 81%. Half (53%) of the patients did not complete their planned therapy due to toxicity (30%), suboptimal response or disease progression (15%), or death on treatment (8%). Overall survival was 40.7 months and progression free survival was 17.7 months. CONCLUSIONS: Our patients were older, had worse disease characteristics and more comorbidities than patients in the VISTA trial. While response rates were similar, survival outcomes appeared worse. Bortezomib-based treatment in the real world setting still carries a high risk of toxicity in the elderly population.

The Feasibility of Electrochemical Ammonia Synthesis in Molten LiCl-KCl Eutectics.

Molten LiCl and related eutectic electrolytes are known to permit direct electrochemical reduction of N2 to N3- with high efficiency. It had been proposed that this could be coupled with H2 oxidation in an electrolytic cell to produce NH3 at ambient pressure. Here, this proposal is tested in a LiCl-KCl-Li3 N cell and is found not to be the case, as the previous assumption of the direct electrochemical oxidation of N3- to NH3 is grossly over-simplified. We find that Li3 N added to the molten electrolyte promotes the spontaneous and simultaneous chemical disproportionation of H2 (H oxidation state 0) into H- (H oxidation state -1) and H+ in the form of NH2- /NH2 - /NH3 (H oxidation state +1) in the absence of applied current, resulting in non-Faradaic release of NH3 . It is further observed that NH2- and NH2 - possess their own redox chemistry. However, these spontaneous reactions allow us to propose an alternative, truly catalytic cycle. By adding LiH, rather than Li3 N, N2 can be reduced to N3- while stoichiometric amounts of H- are oxidised to H2 . The H2 can then react spontaneously with N3- to form NH3 , regenerating H- and closing the catalytic cycle. Initial tests show a peak NH3 synthesis rate of 2.4×10-8  mol cm-2 s-1 at a maximum current efficiency of 4.2 %. Isotopic labelling with 15 N2 confirms the resulting NH3 is from catalytic N2 reduction.