Trace Amounts Of Water Research Articles

Trace-Level Humidity Sensing from Commercial Organic Solvents and Food Products by an AIE/ESIPT-Triggered Piezochromic Luminogen and ppb-Level "OFF-ON-OFF" Sensing of Cu2+: A Combined Experimental and Theoretical Outcome.

Selective and sensitive moisture sensors have attracted immense attention due to their ability to monitor the humidity content in industrial solvents, food products, etc., for regulating industrial safety management. Herein, a hydroxy naphthaldehyde-based piezochromic luminogen, namely, 1-{[(2-hydroxyphenyl)imino]methyl}naphthalen-2-ol (NAP-1), has been synthesized and its photophysical and molecular sensing properties have been investigated by means of various spectroscopic tools. Owing to the synergistic effect of both aggregation-induced emission (AIE) and excited-state intramolecular proton transfer (ESIPT) along with the restriction of C=N isomerization, the probe shows bright yellowish-green-colored keto emission with high quantum yield after the interaction with a trace amount of water. This makes NAP-1 a potential sensor for monitoring water content in the industrial solvents with very low detection limits of 0.033, 0.032, 0.034, and 0.033% (v/v) from tetrahydrofuran (THF), acetone, dimethyl sulfoxide (DMSO), and methanol, respectively. The probe could be used in the food industry to detect trace moisture in the raw food samples. The reversible switching behavior of NAP-1 makes it suitable for designing an INHIBIT logic gate with an additional application in inkless writing. In addition, an Internet of Things-(IoT) based prototype device has been proposed for on-site monitoring of the moisture content by a smartphone via Bluetooth or Wi-Fi. The aggregated probe also has the ability to recognize Cu2+ from a purely aqueous medium via the chelation-enhanced quenching (CHEQ) mechanism, leading to ∼84% fluorescence quenching with a Stern–Volmer quenching constant of 1.46 × 104 M–1 and with an appreciably low detection threshold of 57.2 ppb, far below than recommended by the World Health Organization (WHO) and the United States Environmental Protection Agency (U.S. EPA). The spectroscopic and theoretical calculations (density functional theory (DFT), time-dependent DFT (TD-DFT), and natural bond orbital (NBO) analysis) further empower the understanding of the mechanistic course of the interaction of the host–guest recognition event.

Electrochemically Triggered Chain Reactions for the Conversion of Furan Derivatives.

We report an electrochemical method for coupling biomass-derived C5/C6 compounds to value-added fuel precursors. Using only 2 % of equivalent charges, 2-methylfuran (2-MF) was oxidized to yield a cation radical, which readily reacted with 3-hexene-2,5-dione, a derivate of 2,5-dimethylfuran, to produce 3-(5-methylfuran-2-yl)hexane-2,5-dione. The product was converted to 4-ethylnonane (a component of biodiesel/jet fuel) in a single step in excellent yield. Importantly, the reaction was not sensitive to oxygen, and a trace amount of water was found to promote the reaction. Detailed mechanistic studies confirmed the proposed reaction pathways. Key to the mechanism is the radical generation that is enabled by electrochemistry. The radical is regenerated at the end of a reaction cycle to ensure chain propagation for an average of ca. 47 times, resulting in an apparent Faradaic efficiency of 4700 %.

Electrochemically Triggered Chain Reactions for the Conversion of Furan Derivatives

AbstractWe report an electrochemical method for coupling biomass‐derived C5/C6 compounds to value‐added fuel precursors. Using only 2 % of equivalent charges, 2‐methylfuran (2‐MF) was oxidized to yield a cation radical, which readily reacted with 3‐hexene‐2,5‐dione, a derivate of 2,5‐dimethylfuran, to produce 3‐(5‐methylfuran‐2‐yl)hexane‐2,5‐dione. The product was converted to 4‐ethylnonane (a component of biodiesel/jet fuel) in a single step in excellent yield. Importantly, the reaction was not sensitive to oxygen, and a trace amount of water was found to promote the reaction. Detailed mechanistic studies confirmed the proposed reaction pathways. Key to the mechanism is the radical generation that is enabled by electrochemistry. The radical is regenerated at the end of a reaction cycle to ensure chain propagation for an average of ca. 47 times, resulting in an apparent Faradaic efficiency of 4700 %.

Synthesis of Trialkylamines with Extreme Steric Hindrance and Their Decay by a Hofmann-like Elimination Reaction.

A number of amines with three bulky alkyl groups at the nitrogen, which surpass the steric crowding of triisopropylamine considerably, were prepared by using different synthetic methods. It turned out that treatment of N-chlorodialkylamines with organometallic compounds, for example, Grignard reagents, in the presence of a major excess of tetramethylenediamine offered the most effective access to the target compounds. The limits of this method were also tested. The trialkylamines underwent a dealkylation reaction, depending on the degree of steric stress, even at ambient temperature. Because olefins were formed in this transformation, it showed some similarity with the Hofmann elimination. However, the thermal decay of sterically overcrowded tertiary amines was not promoted by bases. Instead, this reaction was strongly accelerated by protic conditions and even by trace amounts of water. Reaction mechanisms, which were analyzed with the help of quantum chemical calculations, are suggested to explain the experimental results.

Effect of Water Concentration in LiPF6-Based Electrolytes on the Formation, Evolution, and Properties of the Solid Electrolyte Interphase on Si Anodes.

A trace amount of water in an electrolyte is one of the factors detrimental to the electrochemical performance of silicon (Si)-based lithium-ion batteries that adversely affect the formation and evolution of the solid electrolyte interphase (SEI) on Si-based anodes and change its properties. Thus far, a lack of fundamental and mechanistic understanding of SEI formation, evolution, and properties in the presence of water has inhibited efforts to stabilize the SEI for improved electrochemical performance. Thus, we investigated the SEI formed in a Gen2 electrolyte (1.2 M LiPF6 in ethylene carbonate/ethyl methyl carbonate, 3:7 wt %, water content: <10 ppm) with and without additional water (50 ppm) at varying potentials (1.0, 0.5, 0.2, and 0.01 V vs Li/Li+). The impact of additional water on the morphological, (electro)chemical, and structural properties of SEI was studied using microscopic (atomic force microscopy and scanning spreading resistance microscopy) and spectroscopic (X-ray photoelectron spectroscopy, attenuated total reflection Fourier-transform infrared spectroscopy, and time-of-flight secondary ion mass spectrometry) techniques. The SEI exhibits both potential- and water concentration-dependent trends in its morphology and chemical composition. The presence of additional water in the electrolyte causes parasitic reactions, which onset at ∼1.0 V, resulting in a reduction of electrolyte components and result in the formation of an insulating, fluorophosphate-rich SEI. In addition, hydrolysis of LiPF6 creates hydrofluoric acid, which reacts with the surface oxide layer on the Si electrode, leading to a pitted and inhomogeneous SEI structure.

Thermal Stability of a Eutectic Mixture of Bis(2,2‐dinitropropyl) Acetal and Formal: Part C. Kinetic Compensation Effect

AbstractThe aging behavior of a eutectic mixture of bis(2,2‐dinitropropyl) acetal and formal [called NP here] has been studied in various atmospheres [dry (air or nitrogen) versus wet] at temperatures 70 °C and below. The properties of aged samples were analyzed using Fourier transform infrared (FTIR) spectroscopy, Karl Fischer (KF) titration, liquid chromatography/mass spectrometry (LC/MS), and thermogravimetric analysis (TGA) over a period of three years. The results indicate that at aging temperatures up to 55 °C, the initial rates of water production from nitrous acid (HONO) formation and decomposition into the water, NO, and NO2 follows a 1st order rate law and the rate constants follow an Arrhenius law as a function of temperature. The activation energies and pre‐factors for water and volatiles production yield a single linear kinetic compensation plot, suggesting a common degradation pathway between NP and the various combinations of its constituents. Within a narrow temperature range, around 55 °C, a trace amount of water in NP stabilizes its properties by preventing HONO elimination. When the aging temperature is substantially higher than 55 °C, the nature of the degradation mechanism changes. It is suspected that the degradation products of NOx, water, and HNO3 serve as catalysts to auto‐catalyze (kinetics beyond the 1st order) and further degrade NP. The effect of headspace volume on this auto‐catalytic process will be discussed.

Fast-charged aluminum-ion battery with aluminum-graphene nanocomposite anode

Currently, aluminum-ion batteries are considered attractive energy storage devices because aluminum is an inexpensive, widely available, environmentally friendly, low-flammable, and high recyclable electrode material. Electrochemical cell simulating the work of an aluminum-ion battery with aluminum-graphene nanocomposite–negative electrode, positive graphene electrode, and chloroaluminate ionic liquid 1-ethyl-3-methylimidazolium chloride has been designed and tested. The cell exhibits excellent performance and long shelf life. The aluminum-graphene composite is not prone to oxidation over a long period of time. Consequently, the negative electrode surface does not undergo passivation by trace amounts of water and oxygen in the electrolyte during storage, which considerably prolongs the battery shelf life. The analyzed cell delivered stable performance across a wide range of charge/discharge rates for several thousands of cycles without any noticeable loss in capacity and Coulombic efficiency. It has almost 100% Coulombic efficiency at high charge/discharge current densities and retains its characteristics after a 7-day current-free period.

Crucial Role of Water in the Mechanosynthesis of CsPbI3 and Other ABX3 Halides.

Mechanochemical synthesis of CsPbI3 , as a model system for ABX3 halides, was studied. Water was shown to strongly promote the kinetics of formation of CsPbI3 from the CsI+PbI2 mixture through increased mobility of the constituting ionic species. Since many binary and ternary halides are hygroscopic, it was concluded that the presence of small, uncontrollable and unintentional additions of water should often occur in both precursor mixtures and synthesized complex halides boosting the kinetics of formation of many, if not all, ternary organic-inorganic hybrid halides such as, for example, MAPbX3 (X=Cl, Br, I). In addition, trace amounts of water should influence the transport characteristics of complex halides. Thus, the presence of water explains, at least partially, the huge scatter in both the reported mechanochemical reaction times necessary for obtaining single-phase APbX3 perovskite halides and the activation energies of ionic diffusion in APbX3 .

Dual-Functional Electrolyte Additives toward Long-Cycling Lithium-Ion Batteries: Ecofriendly Designed Carbonate Derivatives.

Long-term stability of the solid electrolyte interphase (SEI) and cathode-electrolyte interface (CEI) layers formed on anodes and cathodes is imperative to mitigate the interfacial degradation of electrodes and enhance the cycle life of lithium-ion batteries (LIBs). However, the SEI on the anode and CEI on the cathode are vulnerable to the reactive species of PF5 and HF produced by the decomposition and hydrolysis of the conventional LiPF6 electrolyte in a battery inevitably containing a trace amount of water. Here, we report a new class of cyclic carbonate-based electrolyte additives to preserve the integrity of SEI and CEI in LIBs. This new class of additives is designed and synthesized by an ecofriendly approach that involves fixing CO2 with functional epoxides bearing various reactive side chains. It was found that the cyclic carbonates of 3-(1-ethoxyethoxy)-1,2-propylene carbonate and 3-trimethoxysilylpropyloxy-1,2-propylene carbonate, possessing high capability for the stabilization of Lewis-acidic PF5, exhibit a capacity retention of 79.0% after 1000 cycles, which is superior to that of the pristine electrolyte of 54.7%. Moreover, TMSPC has HF-scavenging capability, which, along with PF5 stabilization, results in enhanced rate capability of commercial LiNi0.6Mn0.2Co0.2O2 (NCM622)/graphite full cells, posing a significant potential for high-energy-density LIBs with long cycle stability.

Organic Ion-associate Phase Extraction/Back-microextraction for the Preconcentration and Determination of Lithium Using 2,2,6,6-Tetramethyl-3,5-heptanedione by Liquid Electrode Plasma Atomic Emission Spectrometry and GF-AAS in Environmental Water.

We developed an ion-associate phase (IAP)-extraction/acid back-extraction system for the preconcentration and atomic spectrometric determination of lithium trace amounts in water. The chelating reagent for lithium also works as a constituent of the extraction phase. The lithium in a 10 mL sample solution was converted through a chelate complex reaction with 2,2,6,6-tetramethyl-3,5-heptanedione (HDPM). The addition of a benzyldimethyltetradecylammonium ion caused the formation of IAP suspension in the solution. Centrifugation of the solution led to the isolation of a liquid organic phase and the lithium complex was extracted as the upper phase from the centrifuge tube. After the aqueous phase was removed, lithium was back-extracted with a 400 μL nitric acid solution from the IAP. The acid phase was measured using liquid-electrode-plasma atomic-emission-spectrometry (LEP-AES) or graphite-furnace atomic-absorption spectroscopy (GF-AAS). The detection limits were 0.02 mg/L for LEP-AES and 0.02 μg/L for GF-AAS. This system was applied to the determination of environmental water. The HDPM in the organic phase was reusable.

Aldehyde as a Traceless Directing Group for Regioselective C-H Alkylation Catalyzed by Rhodium(III) in Air.

The aromatic aldehyde as a traceless directing group for the regionselective C-H alkylation catalyzed by rhodium(III) under aerobic atmospheric conditions has been developed. The process involves an aldehyde assisted direct addition of C-H bond to unsaturated electrophiles of acrylates or acrylic acids, and the subsequent decarbonylation. A trace amount of water is found to favor the reaction.

Unusual Effect of Trace Water on the Structure and Activity of Nix Co1-x Electrocatalysts for the Methanol Oxidation Reaction.

Highly active Ni-based catalysts have attracted much attention but are still facing challenges owing to the immature synthetic method. Herein, polyhedral Nix Co1-x alloy was prepared by a facile modified polyol method in which a trace amount of water could halve the particle size of the alloy. The Ni/Co ratios in Nix Co1-x alloy strictly depended on the used amount of water owing to the different solubilities of the precursors. Among them, the Ni0.6 Co0.4 nanoparticles obtained with 70 μL of deionized water exhibited the best performance in the methanol oxidation reaction with a peak current density of 116 mA cm-2 in the presence of 1 m NaOH+0.5 m CH3 OH solution, which is higher than those of Ni0.7 Co0.3 (80 mA cm-2 ) and Ni0.5 Co0.5 (33 mA cm-2 ). The excellent performance of Ni0.6 Co0.4 is attributed to the unique structure with appropriate Ni/Co ratio, which elongates the C-O bond in methanol and lowers the reaction free energy according to DFT calculations.

In situ tumor-triggered subcellular precise delivery of multi-drugs for enhanced chemo-photothermal-starvation combination antitumor therapy.

Rationale: Drug combination therapy for cancer treatment exerts a more potent antitumor effect. The targeted delivery and release of multiple drugs in a patient's body thus presents a more effective treatment approach, warranting further research. Methods: Two antitumor drugs (ICG: indocyanine green and THP: pirarubicin) were successfully screened to sequentially trigger self-assembling peptides (P60) to produce bacteria-sized particles (500-1000 nm, P60-ICG-THP). First, after mixing equal amount of P60 and ICG, trace amount of water (the mass ratio between P60 and water: 100:1) was used to trigger their assembly into P60-ICG. Subsequently, the assembly of P60-ICG and THP was further triggered by ultrasound treatment to produce P60-ICG-THP. Results: P60-ICG-THP constituted a cluster of several nanoparticles (50-100 nm) and possessed a negative charge. Owing to its size and charge characteristics, P60-ICG-THP could remain outside the cell membrane, avoiding the phagocytic clearance of blood and normal tissue cells in vivo. However, after localizing in the tumor, the size and charge switches of P60-ICG-THP, rapidly triggered by the low pH of the tumor microenvironment, caused P60-ICG-THP to segregate into two parts: (i) positively charged nanoparticles with a size of approximately 50 nm, and (ii) negatively charged particles of an uneven size. The former, mainly carrying THP (chemotherapeutic agent), could immediately cross the cell membrane and deliver pirarubicin into the nucleus of tumor cells. The latter, carrying ICG (used for photothermal therapy), could also enter the cell via the endocytosis pathway or accumulate in tumor blood vessels to selectively block the supply of nutrients and oxygen (cancer starvation). Both these particles could avoid the rapid excretion of ICG in the liver and were conducive to accumulation in the tumor tissue for photothermal therapy. Conclusion: Our drug delivery system not only achieves the precise subcellular delivery of two anticancer drugs due to their size and charge switches in the tumor site, but also provides a new strategy to combine chemotherapy, photothermal therapy, and cancer starvation therapy for the development of a highly efficient antitumor therapeutic regimen.

The Effect of Water Concentration in Carbonate-Based Electrolytes on the Si Anode/Electrolyte Interface

Lithium-ion batteries (LiBs) have been successfully utilized as power sources in various applications ubiquitous in our daily lives, ranging from portable electronic devices to electric vehicles. To meet the increasing energy demand, however, development of LiBs with a higher energy density is inevitable. Using silicon (Si) as an anode is promising due to its high theoretical capacity (approximately 4200 mAhg-1), appropriate operating voltage (~0.4 V vs. Li/Li+), abundance, and environmentally benign nature.1 Despite the aforementioned advantages, several challenges remain before the commercial utilization of Si anodes, namely the low conductivity of its readily-formed surface oxide (SiO2), a large volume change (up to 400 %) during lithiation/delithiation, and the instability of Si/electrolyte interface (SiEI).2-3 As the large volume change leads to fracture and continuous evolution of SiEI, achieving a stable SiEI is a key to developing successful LiBs with Si anodes. Water, which is known to react with LiPF6 salt in carbonate-based electrolytes to generate corrosive hydrofluoric acid (HF),4 is a source for the electrode/electrolyte interface destabilization. Thus, it is essential to understand how the presence of even trace amounts of water in the system affects the interfacial chemistry of the LiB electrodes. While the performance of LiBs with graphite or lithium titanate negative electrodes have been previously studied with excess water in the electrolyte,5-6 information on the effect of water concentration in the electrolyte on Si anodes, and the SiEI in particular, is limited. In this work, we evaluated the electrochemical performance of Si anodes in a standard electrolyte (1.2 M LiPF6 in EC:EMC (3:7 wt%)) with varying concentration of water (10 - 1,000 ppm). Subsequent analyses on the cycled Si anodes were performed utilizing a variety of surface and bulk characterization techniques. The surface chemistry (e.g., composition and evolution) of SiEI was analyzed using Fourier-transform infrared spectroscopy (FTIR), Raman spectroscopy, time-of-flight secondary ion mass spectrometry (TOF-SIMS), and X-ray photoelectron spectroscopy (XPS). Surface morphologies of cycled Si anodes were measured with tapping-mode atomic force microscopy (AFM), and the surface resistivities were mapped in contact-mode with scanning spreading resistance microscopy (SSRM). The information obtained is utilized to understand water concentration effects on the properties, reactivity, and evolution of the SiEI and the electrochemical cell performance. References Feng, K.; Li, M.; Liu, W.; Kashkooli, A. G.; Xiao, X.; Cai, M.; Chen, Z., Silicon-Based Anodes for Lithium-Ion Batteries: From Fundamentals to Practical Applications. Small 2018, 14 (8), 1702737.Chae, S.; Ko, M.; Kim, K.; Ahn, K.; Cho, J., Confronting Issues of the Practical Implementation of Si Anode in High-Energy Lithium-Ion Batteries. Joule 2017, 1 (1), 47-60.Philippe, B.; Dedryvere, R.; Allouche, J.; Lindgren, F.; Gorgoi, M.; Rensmo, H.; Gonbeau, D.; Edstrom, K., Nanosilicon Electrodes for Lithium-Ion Batteries: Interfacial Mechanisms Studied by Hard and Soft X-ray Photoelectron Spectroscopy. Chem. Mater. 2012, 24 (6), 1107-1115.Xu, K., Nonaqueous Liquid Electrolytes for Lithium-Based Rechargeable Batteries. Chem. Rev. 2004, 104 (10), 4303-4417.Burns, J. C.; Sinha, N. N.; Jain, G.; Ye, H.; VanElzen, C. M.; Scott, E.; Xiao, A.; Lamanna, W. M.; Dahn, J. R., The impact of intentionally added water to the electrolyte of Li-ion cells. I. Cells with graphite negative electrodes. J. Electrochem. Soc. 2013, 160 (11), A2281-A2287.Burns, J. C.; Sinha, N. N.; Jain, G.; Ye, H.; Van Elzen, C. M.; Scott, E.; Xiao, A.; Lamanna, W. M.; Dahn, J. R., The impact of intentionally added water to the electrolyte of Li-ion cells: II. Cells with lithium titanate negative electrodes. J. Electrochem. Soc. 2014, 161 (3), A247-A255.

Stability of the oxidized form of RuLL′(NCS)2 dyes in acetonitrile in the presence of water and pyridines – Why the dye-sensitized solar cell electrolyte should be dry

The detrimental effect of electrolyte water contamination on the light-soaking lifetime of Dye-sensitized Solar Cells (DSCs) prepared with RuLL′(NCS)2 dyes and N-additives like 4-tert-butylpyridine (TBP) is not well understood. A new explanation is presented based on investigation of the stability of the ruthenium(III) complexes Ru(bipy)2(NCS)2+ (1+) and RuLL′(NCS)2+ (L = 4,4′-dicarboxy-2,2′-bipyridine, L′= 4,4′-nonyl-2,2′-bipyridine) (Z907+) in acetonitrile in the presence of water and pyridines covering a large variation in basicity. 1+ reacts with small amounts of water in the acetonitrile containing a pyridine base (X) according to the overall reaction: 6Ru(bipy)2(NCS)2+ + 4H2O + 8X → 5Ru(bipy)2(NCS)2 + Ru(bipy)2(NCS)(CN) + SO42− + 8XH+. The reaction mechanism of 1+ (and Z907+) is proposed to be initiated by an attack of OH− giving Ru(bipy)2(NCS)(NCS-OH). The stronger the base the faster the reaction. Extrapolating the life time of Z907+ to a typical TBP concentration of 0.5 M in the DSC gives a degradation rate around 7 s−1. Z907+ bound to a layer of nano crystalline TiO2 surface reacted fast too, when inserted in an acetonitrile solution containing 4-tert-butylpyridine. In a “wet” electrolyte, containing more than 500 mM of water the light-soaking lifetime of a DSC prepared with Z907 is predicted to be about 10 days at out-door light soaking conditions, whereas trace amounts of water (<25 mM) in a “dry” electrolyte is used up by consumption of only 10% of the Z907 in a typical DSC. Therefore, the DSC is expected to have a long light-soaking lifetime with a “dry” electrolyte.

“110th Anniversary:” Interactions of Bis(1-methyl-1-phenylethyl) Peroxide with the Secondary Antioxidant Bis(octadecyloxycarbonylethyl) Sulfide: Mechanistic Studies Conducted in Dodecane as a Model System for Polyethylene

Cross-linked polyethylene (XLPE) is an important class of materials with critical applications including pipes and high voltage electric cables. An organic peroxide such as bis(1-methyl-1-phenylethyl) peroxide (BMPEP) is a commonly used radical initiator in the cross-linking process along with a secondary antioxidant such as bis(octadecyloxycarbonylethyl) sulfide (BOCES). Herein is described a detailed investigation into the complex interactions of the radical initiator BMPEP and the secondary antioxidant BOCES in dodecane solvent–a model for the polyethylene polymer. Kinetic and spectroscopic experiments along with DFT calculations provide the foundation for a detailed mechanistic description for the roles of BMPEP, BOCES, atmospheric oxygen, and trace amounts of water in the overall process.

Electrodeposition of Lithium in LiPF6-Based Electrolyte with Trace-Amount of Water

Lithium metal has been considered as an attractive candidate of the anode material for the next-generation secondary batteries because of its high theoretical capacity and low redox potential. Among a lot of strategies in order to suppress the inhomogeneous or dendritic growth of lithium during deposition have been proposed so far, some reports suggested that the trace-amount of water leads to smooth the morphology of deposited lithium metal. (1, 2) However, the relationship between the morphology of deposited lithium metal and the content of the electrolyte which changes with the time after addition of the water is not clear. In the present study, we investigated the electrodeposition of lithium in LiPF6-based electrolyte with trace-amount of water. Especially, we focused on the change of the morphology and surface state of the deposited lithium metal with the content of the electrolyte. 100 ppm of water was added into 1.0 mol dm–3 LiPF6 in propylene carbonate (PC) in the Ar-filled glove box and temporal change of its water content was checked by Karl-Fischer titration method. The water content was gradually decreased with time due to the reaction of LiPF6 and water. (3) When the electrodeposition of lithium was conducted on the copper electrode in the electrolyte, the morphology of the deposited lithium changed from inhomogeneous to granular and smooth as time passes after addition of water. This result proposed that the decomposed product in the electrolyte was strongly affected to the morphology of the deposit. (4) We also checked the surface state of the deposits by auger electron spectroscopy, X-ray and hard X-ray photoelectron spectroscopy, suggesting that the component of the film greatly influences the morphology of the deposit. Acknowledgement This work was supported by the New Energy and Industrial Technology Development Organization (NEDO) under the “Research and Development Initiative for Scientific Innovation of New Generation Batteries 2 (RISING2)” References J. Qian, W. Xu, P. Bhattacharya, M. Engelhard, W. A. Henderson, Y. Zhang and J.-G. Zhang, Nano Energy, 15, 135 (2015).H. Koshikawa, S. Matsuda, K. Kamiya, Y. Kubo, K. Uosaki, K. Hashimoto and S. Nakanishi, J. Power Sources, 350, 73 (2017).D. Strmcnik, I. E. Castelli, J. G. Connell, D. Haering, M. Zorko, P. Martins, P. P. Lopes, B. Genorio, T. Østergaard, H. A. Gasteiger, F. Maglia, B. K. Antonopoulos, V. R. Stamenkovic, J. Rossmeisl and N. M. Markovic, Nature Catalysis, 1, 255 (2018).K. Kanamura, S. Shiraishi and Z. Takehara, J. Electrochem. Soc., 143, 2187 (1996).

Anomalous anodic layer growth on titanium occurring in electrolyte comprising nitrate and water

The anodization of a titanium substrate using an aqueous nitrate solution led to an anomalous surface covered with a collapsed-like structure, and a homogenous oxide layer was never obtained, which is different to the case of most aqueous electrolytes. The objective of this study was to elucidate the primary cause inducing this anomalous layer growth that occurs in an aqueous nitrate electrolyte. To this end, the anodization of a titanium substrate was conducted using a non-aqueous electrolyte consisting of ethylene glycol and ammonium nitrate, wherein a trace amount of water was added. Microscopic analysis revealed that the addition of only 2% water into the electrolyte induced the growth of the anomalous layer, while the non-aqueous electrolyte without water addition resulted in a homogenous layer. Regardless of the water addition, the formed surface was comparatively flat at the initial stage. However, cabbage-like precipitates appeared and increased with the treatment time only in the case of water addition, and subsequently gradually converted to a collapsed-like surface. Nitric ions coexisting with water were capable of capturing an electron from the molecule oxygen ions in the anodic layer, and thereby developed the oxygen-filled cavity. The generation of a local spark at the cavity led to the formation of the cabbage-like precipitates, and thus, the layer growth did not proceed normally.

The influence of CO, CO2 and H2O on selective CO methanation over Ni(Cl)/CeO2 catalyst: On the way to formic acid derived CO-free hydrogen

For the first time the influence of CO, CO2 and H2O content on the performance of chlorinated NiCeO2 catalyst in selective or preferential CO methanation was studied systematically. It was shown that the rate of CO methanation over Ni(Cl)/CeO2 increases with the increasing H2 concentration, is independent of CO2 concentration and decreases with increasing CO and H2O concentrations; the rate of CO2 methanation is weakly sensitive to H2 and CO2 concentrations and decreases with increasing CO and H2O concentrations. High catalyst selectivity was attributed to Ni surface blockage by strongly adsorbed CO molecules and ceria surface blockage by Cl, which both inhibit CO2 hydrogenation.For the first time, selective CO methanation over Ni(Cl)/CeO2 was studied for deep CO removal from formic acid derived hydrogen-rich gases characterized by high CO2 (40–50 vol%), low CO (30–1000 ppm) content and trace amounts of water. Composite Ni(Cl)/CeO2-η-Al2O3/FeCrAl wire mesh catalyst was demonstrated to be effective for this process at temperatures of 180–220°С, selectivity 30–70%, WHSV up to 200 L (STP)/(g∙h). The catalyst provides high process productivity, low pressure drop, uniform temperature distribution, and appears highly promising for the development of a compact CO cleanup reactor. Selective CO methanation was concluded to be a convenient way to CO-free hydrogen produced by formic acid decomposition.

Ice-VII-like molecular structure of ambient water nanomeniscus

Structural transformations originating from diverse rearrangements of the hydrogen bonding in water create various phases. Although most phases have been well investigated down to the molecular level, the molecular structure of the nanomeniscus, a ubiquitous form of nanoscale water in nature, still remains unexplored. Here, we demonstrate that the water nanomeniscus exhibits the stable, ice-VII-like molecular structure in ambient condition. Surface-enhanced Raman spectroscopy on trace amounts of water, confined in inter-nanoparticle gaps, shows a narrowed tetrahedral peak at 3340 cm-1 in the OH-stretching band as well as a lattice-vibrational mode at 230 cm-1. In particular, the ice-VII-like characteristics are evidenced by the spectral independence with respect to temperature variations and differing surface types including the material, size and shape of nanoparticles. Our results provide un unambiguous identification of the molecular structure of nanoconfined water, which is useful for understanding the molecular aspects of water in various nanoscale, including biological, environments.