Perchloric Research Articles

In Situ Surface X-Ray Diffraction Studies of the Electrochemical Double Layer on Pt(111)

The molecular structure of the electrochemical double layer is an important fundamental topic in interfacial electrochemistry. It has received renewed interest in the last years, because of its influence on many electrochemical reactions and the emergence of ab initio molecular dynamics simulations that allow a detailed description of the interface structure and dynamics [1,2]. In the measurements presented here, we investigated the properties of the electrochemical double layer on Pt(111) via in situ surface X-ray diffraction (SXRD), a technique that is well-established for single crystal studies [3-7].Platinum electrodes are widely used as electrocatalysts, for example as cathodes in proton exchange membrane fuel cells due to their high ORR reactivity. The single-crystalline Pt(111) surface, which is a well studied model system, is especially interesting for studies of the electrochemical double layer. Recent electrochemical measurements revisited this system and found evidence for a double layer structure that strongly deviated from the traditional Gouy-Chapman-Stern model and indicated a complex structural influence of water [8,9]. The water structure within the electrochemical double layer is also of major interest in computational studies. For non-adsorbing, aqueous electrolyte the electrode surface charge can be partly compensated by a layer of oriented water molecules due to their dipole moment. For potentials around the potential of zero charge (PZC), a potential-dependent orientation of water molecules with respect to the electrode surface was suggested [1,2,10].To investigate the arrangement and orientation of the water molecules near the Pt(111) surface we used in situ SXRD methods, focussing on X-ray reflectivity (XRR) and crystal truncation rod (CTR) analysis. These methods allow to acquire detailed information about the electrode surface structure as well as the electrochemical double layer. By measuring multiple CTR sets at different surface potentials, information on the potential-dependence of the interface processes can be obtained. The experiments were performed at beamline ID31 of the European Synchrotron Radiation Facility using high photon energies of 75 keV, which provide very large data sets. This allows significantly improved structural modeling as compared to conventional SXRD. The studies employed an electrochemical hanging-meniscus X-ray diffraction cell that allows for SXRD measurements of fast dynamic systems in a well-defined electrochemical environment. We will report results on the water structure in the double layer obtained in perchloric acid at potentials around the PZC.We gratefully acknowledge financial support by the Deutsche Forschungsgemeinschaft via project no. 418603497 and the BMBF via 05K19FK3 and 05K22FK1.

A Guide for the Electrochemical Stability of Thiolate Self-Assembled Monolayers on Gold in Various Electrolytes

Self-assembled monolayers (SAMs) are widely used in surface chemistry to modify surfaces for various applications such as biosensing1, electronics2, and electrocatalysis3. SAMs are attractive due to their high surface coverage and stability. Although studies have been conducted to test the effects of temperature, air exposure, and solvent degradation on SAMs stability 4,5, the electrochemical stability of SAMs has not been as extensively studied. Existing literature on this topic mainly focuses on the reductive desorption limits of thiolate SAMs in alkaline conditions6,7. Recent work by Ramos et al. demonstrated pH-dependent stable potential windows in which SAMs remained intact on electrode surfaces of different metals8. However, there is still a need to verify and expand on this work.To address this need, we aim to create a comprehensive guide on the electrochemical stability of thiolate SAMs on gold electrodes. We will use cyclic voltammograms (CV), electrochemical impedance spectroscopy (EIS), and electrochemical surface plasmon resonance (EC-SPR) to probe and verify the stable electrochemical potential windows in both aqueous and non-aqueous electrolytes. We have conducted studies on three aqueous solutions at three distinct pH, perchloric acid, potassium hydroxide, and sodium chloride. For non-aqueous solvents we tested a wide range of different organic solvents including acetonitrile, dimethylformamide, propylene carbonate, and various alcohols. Our findings demonstrate that the main factor for SAM stability in aqueous and non-aqueous electrolytes is the pH and solubility of the SAM, respectively. Our poster will present our current work and outlook on this topic.(1) Dauphin-Ducharme, P.; Ploense, K. L.; Arroyo-Currás, N.; Kippin, T. E.; Plaxco, K. W. Electrochemical Aptamer-Based Sensors: A Platform Approach to High-Frequency Molecular Monitoring In Situ in the Living Body. In Biomedical Engineering Technologies: Volume 1; Ossandon, M. R., Baker, H., Rasooly, A., Eds.; Methods in Molecular Biology; Springer US: New York, NY, 2022; pp 479–492. https://doi.org/10.1007/978-1-0716-1803-5_25.(2) Hatton, R. A.; Willis, M. R.; Chesters, M. A.; Rutten, F. J. M.; Briggs, D. Enhanced Hole Injection in Organic Light-Emitting Diodes Using a SAM-Derivatised Ultra-Thin Gold Anode Supported on ITO Glass. J. Mater. Chem. 2003, 13 (1), 38–43. https://doi.org/10.1039/B208169P.(3) Shang, H.; Wallentine, S. K.; Hofmann, D. M.; Zhu, Q.; Murphy, C. J.; Baker, L. R. Effect of Surface Ligands on Gold Nanocatalysts for CO2 Reduction. Chem. Sci. 2020, 11 (45), 12298–12306. https://doi.org/10.1039/D0SC05089J.(4) Schlenoff, J. B.; Li, M.; Ly, H. Stability and Self-Exchange in Alkanethiol Monolayers. J. Am. Chem. Soc. 1995, 117 (50), 12528–12536. https://doi.org/10.1021/ja00155a016.(5) Laibinis, P. E.; Whitesides, G. M. Self-Assembled Monolayers of n-Alkanethiolates on Copper Are Barrier Films That Protect the Metal against Oxidation by Air. J. Am. Chem. Soc. 1992, 114 (23), 9022–9028. https://doi.org/10.1021/ja00049a038.(6) Salvarezza, R. C.; Carro, P. The Electrochemical Stability of Thiols on Gold Surfaces. J. Electroanal. Chem. 2018, 819, 234–239. https://doi.org/10.1016/j.jelechem.2017.10.046.(7) Beulen, M. W. J.; Kastenberg, M. I.; van Veggel, F. C. J. M.; Reinhoudt, D. N. Electrochemical Stability of Self-Assembled Monolayers on Gold. Langmuir 1998, 14 (26), 7463–7467. https://doi.org/10.1021/la981031z.(8) Ramos, N.; Medlin, J. W.; Holewinski, A. Electrochemical Stability of Thiolate Self-Assembled Monolayers on Au, Pt, and Cu; preprint; Chemistry, 2022. https://doi.org/10.26434/chemrxiv-2022-dt7dk. Figure 1

Mechanisms of Stabilization and Degradation of Transition Metal Oxygen Electroreduction Catalysts with in-Situ Electrochemical Flow Cell ICP-MS

Proton exchange membrane hydrogen fuel cell (PEMFC) deployment is presently limited by the high material cost of oxygen reduction reaction (ORR) electrocatalysts at the cathode. Developing low-cost, earth-abundant alternatives for use in acidic environments presents a material stability challenge, especially for long-term device operation. Platinum (Pt)-based materials are used in typical commercial PEMFC cathode formulations due to their simultaneous high performance and long-term stability despite the prohibitively high material cost. Developing lower-cost, longer-life catalyst materials based on earth abundant transition metals can accelerate the adoption of PEMFC technology. The impact of potential, current density, and local microenvironment has been shown to cause degradation of non-Pt materials but standard ex situ measurements can only probe surface restructuring and cumulative dissolution after operation. Material-specific degradation mechanisms that are strong functions of the operating conditions cannot be ascertained without in situ quantification of material degradation under PEMFC-relevant conditions. Information about the degradation pathways of these non-precious catalysts can assist with material design for devices; however, most efforts towards developing an in-situ understanding of PEMFC cathode catalyst degradation under operating conditions are generally limited to Pt-based materials. Extensive in situ characterization has revealed Pt-specific mechanistic information about corrosion pathways as well as conditions that exacerbate Pt alloy leaching. It has been hypothesized that the Pt degradation processes are related to oxide formation under potential cycling. With this critical in-situ information, Pt conditioning protocols have been developed to enhance material lifetime; however, investigations on non-precious materials are less common. Insights into non-precious catalyst degradation in PEMFC operating conditions are not as well-established but could be essential in enabling low-cost materials for commercial use. There is a need for more insights into a vast array of materials which necessitates the development of faster, preferably benchtop techniques for degradation analysis.In this work, we use an in situ electrochemical flow cell assembly and coupled it with an inductively coupled plasma-mass spectrometer (ICP-MS) to quantify the loss of material in real time for several non-Pt materials under reaction conditions. The flow cell is fed by a peristaltic pump at 2.5 mL/min of gas-saturated acidic electrolyte for optimal mass transport. The cell has a three-electrode configuration with a compression-mounted metal foil working electrode, silver/silver chloride reference electrode, and Pt counter electrode downstream of other components. We evaluate a variety of transition metals across the spectrum of ORR activity: palladium, silver, nickel, copper, manganese, and cobalt. Each metal is tested under oxygen and nitrogen saturation in five electrolytes of identical pH: perchloric acid, sulfuric acid, nitric acid, hydrochloric acid, and hydrobromic acid. This setup allows for nearly real time measurement of ORR kinetics and in situ element-specific dissolution rates as a function of time. With careful design of experimental conditions and controlled variables, we are able to suggest mechanisms of degradation with specific reference to conditions under which material loss occurred such as high/low potential, oxygen-saturated/nitrogen-saturated electrolyte, or faradaic/non-faradaic current. We find some metals are stable under nitrogen-saturated electrolyte but corrode more under oxygen-saturated electrolyte only while ORR active. Furthermore, other metals are stable in nitrogen saturated electrolyte at all tested electrochemical conditions but unstable under oxygen saturated electrolyte but only outside the ORR range, implying that cathodic faradaic processes might be stabilizing the surface at low potentials. This stabilization where a thermodynamically unstable material (based on its Pourbaix diagram) exhibits greater immunity while performing ORR in certain electrolytes could inform the development stability mechanisms that direct the design of next generation, non-precious PEMFC cathode catalyst materials. With combined in situ catalyst stability analysis in five pH 1 electrolytes, we can recommend specific conditions for optimizing activity and stability based on the potential range of operation and the electrolyte composition/saturation. We can also distill mechanistic insights from these experiments by creating models that validate causes of catalyst degradation. These models are built using “graphical causal modeling”, which is a mathematical field that goes beyond correlative predictions by venturing into causal inference. We hope to expand this framework into other electrocatalytic reactions of interest. The in-situ ICP-MS electrochemical flow cell setup exhibits promise for accelerating materials stability analysis for enabling next generation Pt-free ORR electrocatalysts through practical experiments and direct comparability to established electrochemical techniques.

Modeling the Environment-Dependent Kinetics of Oxygen Reduction Reaction – a Continuum Model for Electric Double Layer

For proton-exchange-membrane fuel cells (PEMFCs) to achieve broad commercialization, improved energy-conversion efficiency with minimal Pt-based electrocatalyst is required [1]. Because the sluggish rate of oxygen reduction reaction (ORR) limits the efficiency of PEMFCs [2], the efficiency improvement requires a better understanding of ORR kinetics and mechanism to design better catalyst. To understand the ORR mechanism, theoretical and experimental analyses have been conducted. While previous studies reasonably explained the catalyst-dependent activity on single crystal catalysts in 0.1 M perchloric acid solution [3, 4], the explicit effect of electrolyte and related microenvironments [5, 6] is not thoroughly understood. The change in the electrolyte alters the electric-double-layer (EDL) structure and thus the local microenvironment at the electrode/electrolyte interface. Thus, the structure of the EDL should be carefully analyzed to uncover the electrolyte-dependent reaction kinetics. In this talk, we propose a multiscale continuum model to predict the EDL structure and examine the effect of perchloric acid concentration on ORR activity on Pt (111). The model includes Density Potential Functional Theory (DPFT) for electron density and Modified Poisson Boltzmann equation for species’ density and electric potential [7]. Also, the interaction between adsorbents and electric field is taken into account by minimizing the grand potential. After model validation with experimentally measured double-layer capacity data as a function of applied potential and concentration, the effect of the perchloric acid concentration (0.02 M – 0.2 M) on ORR activity is analyzed and discussed. It is shown that the model reproduces the specific activity obtained in the experiments when assuming the oxygen adsorption is limiting the rate, which can be attributed to the large energetic barrier for solvent reorganization [8]. Then, extension of the model to PEMFC ionomer electrolytes will be introduced. Overall, the model framework and findings provide insights into the ORR mechanism and guidance on how to tailor catalyst materials for increased PEMFC performance. Acknowledgements: This work was partially supported by the Hydrogen and Fuel Cell Technologies Office (HFTO), Office of Energy Efficiency and Renewable Energy, U.S. Department of Energy (DOE) through the Million Mile Fuel Cell Truck (M2FCT) consortia, technology managers G. Kleen and D. Papageorgopoulos, under contract number DE-AC02- 05CH11231, as well as by a CRADA with Toyota Central R&D Labs., Inc.. Reference [1] D. A. Cullen, K. C. Neyerlin, R. K. Ahluwalia, R. Mukundan, K. L. More, R. L. Borup, A. Z. Weber, D. J. Myers and A. Kusoglu, Nature Energy, 6, 462 (2021).[2] I. E. L. Stephens, A. S. Bondarenko, U. Grønbjerg, J. Rossmeisl and I. Chorkendorff, Energy & Environmental Science, 5 (2012).[3] M. Shibata, M. Inaba, K. Shinozaki, K. Kodama and R. Jinnouchi, Journal of The Electrochemical Society, 169 (2022).[4] H. A. Hansen, V. Viswanathan and J. K. Nørskov, The Journal of Physical Chemistry C, 118, 6706 (2014).[5] K. Kodama, K. Motobayashi, A. Shinohara, N. Hasegawa, K. Kudo, R. Jinnouchi, M. Osawa and Y. Morimoto, ACS Catalysis, 8, 694 (2017).[6] M. Luo and M. T. M. Koper, Nature Catalysis, 5, 615 (2022).[7] J. Huang, J Chem Theory Comput, 19, 1003 (2023).[8] D. T. Limmer, A. P. Willard, P. Madden and D. Chandler, Proceedings of the National Academy of Sciences, 110, 4200 (2013).

Hydrogen Video Imaging System for Visualizing Microstructure-Dependent Hydrogen Diffusion Behaviors in Polycrystalline Metals

Hydrogen diffusion in polycrystalline metals is known to depend on microstructure. The hydrogen-microstructure interactions have been extensively studied last decades, but the microstructure-dependent hydrogen diffusion behavior is still unclear. To clarify the hydrogen diffusion behavior, it is necessary to visualize the time variations of the microscopic hydrogen distribution in polycrystalline metals. Thus, we developed a hydrogen video imaging system (HVIS) in this study to analyze the hydrogen distribution in polycrystalline metals with sub-micrometer spatial and video-rate time resolutions. The inexpensive and atmospheric-control-free system is expected to be widely used as a versatile approach for analyzing the hydrogen-microstructure interaction in detail.Pure polycrystalline Ni (thickness: 125 µm) was used as a specimen. The specimen was electrochemically polished at a constant voltage of 50 V in a mixed solution of perchloric acid and acetic acid. The thickness was approximately 110 µm after polishing. Subsequently, a polyaniline layer (PANI) was polymerized on one side of pure Ni. The specimen was set to the acrylic cell, which is used to preserve a 0.1 M NaOH aqueous solution. So, only the bare Ni side of the specimen was exposed to the 0.1 M NaOH solution. Electrochemical hydrogen charging was conducted at the bare Ni side of the specimen at a constant current density of -10 A / m2. An inverted optical microscope was used to observe the color distribution of the PANI side. In our previous studies,1-3) it has been clarified that PANI changes its color due to the reaction with hydrogen in metals. Thus, the distribution of hydrogen permeated through pure polycrystalline Ni can be observed as a color distribution of PANI during hydrogen charging.The color of PANI was purple before the hydrogen charging. After 20 h of hydrogen charging, the color of PANI partially turned white. If PANI reacts with hydrogen, the color changes from purple or dark blue to yellow or transparent.1,2) Therefore, the local whitening of PANI is thought to be caused by the reaction with atomic state hydrogen permeated through pure polycrystalline Ni. The number of color changed areas increased with time during hydrogen charging. After 120 h of hydrogen charging, the specimen was immersed in a 1 M NaOH aqueous solution to remove PANI. Subsequently, the microstructure of pure polycrystalline Ni was analyzed using FE-SEM and EBSD. It was found that the color changed area of PANI corresponded to the grain boundaries (GBs) of pure Ni. This suggests that the GBs in pure Ni are preferential hydrogen diffusion paths. Furthermore, the clear color change of PANI was observed at the random GBs, while the whitening scarcely occurred at the Σ3 GBs, indicating that the preferential hydrogen diffusion mainly occurred at the random GBs. The results showed that HVIS can clarify the microstructure-dependent hydrogen diffusion in polycrystalline metals.

OER Activity of Iridium Nanoparticle Catalysts By RDE and Comparison with MEAs

To accelerate the deployment of green hydrogen, lowering the cost of water electrolyzer is one of the important issues. Iridium anode catalyst is a key material for highly efficient and stable operation of proton exchange membrane (PEM) water electrolyzer, however, limited resources of iridium lead to higher cost and the limited availability. Therefore, there is a strong need to develop novel catalysts that can reduce iridium usage without compromising on activity. Rotating electrode half-cell is a useful technique for OER activity measurement of anode catalysts [1], however broader consensus about the activity measurement protocol is still missing. In addition, it is also unclear whether the measured activity values from the RDE are consistent with those of the MEA. The RDE activity is influenced by various measurement parameters; catalyst loading on the disk electrode, ionomer content, electrolyte conductivity, potential range etc. Here, we demonstrate the impact of these RDE parameters on the measured OER activity using various iridium catalysts [2]. The OER activity was evaluated by linear sweep voltammogram at a scan rate of 1 mV sec-1 and a disk rotation rate of 3,600 rpm to minimize the contribution of capacitive current and mass transfer loss due to O2 bubbles. Too much catalyst loading on the disk electrode leads to a decrease in apparent OER activity, so that catalyst loading should be in the range where the catalyst activity is independent of the loading amount. Electrolyte solution was also found to have a significant effect on OER activity; comparing to the activity in perchloric acid solution (0.1 M HClO4), sulfuric acid solution (0.05 M H2SO4) and phosphoric acid (0.1 M H3PO4) showed 60% and 40% activity, respectively. To verify the obtained values of OER activity by RDE at the optimized condition, the OER activities were also determined by MEAs at corresponding conditions. The OER activities of MEA and RDE were found to be approximately the same regardless of catalyst species. Detailed measurement conditions and results will be discussed at the Meeting. References S. M. Alia, G. C. Anderson, J. Electrochem. Soc., 166 (2019) F282. T. Ioroi, T. Nagai, Z. Siroma, K. Yasuda, Int. J. Hydrogen Energy, 47 (2022) 38506.

Electrochemical investigations and antimicrobial activity of Au nanoparticles photodeposited on titania nanoparticles

Titanium oxide nanopowder (TiO2 NPs) was synthesized via anodization in 0.7 M perchloric acid then annealed in nitrogen at 450 °C for 3 h to prepared the Titanium Oxide Nitrogen annealed nanoparticles (TiO2 NPs-N2) powder as catalytic support. Using a photodeposition process, gold was added with isopropanol as a sacrificial donor and H[AuCl4] acid, producing gold nanoparticles on nitrogen-annealed titanium oxide nanoparticles (Au-NPs on TiO2-NPs-N2). The mass loading of Au NPs was 2.86 × 10−4 (g/cm2). TEM images of Au NPs on TiO2-NPs-N2 suggest circular particles with a tendency to agglomerate. Cyclic voltammetry (CV) was used to investigate the electrocatalytic performance of the Au NPs/TiO2-NPs-N2 catalysts in ferrocyanide, KOH, and H2SO4, and the results were compared to those of a polycrystalline Au electrode that is readily accessible in the market. In KOH, H2SO4, and (2 M KOH + 0.1 M glycerol) solutions, the Au NPs/TiO2-NPs-N2 electrode displayed a startlingly high electrocatalytic performance. Using CV, the electrocatalytic oxygen reduction reaction (ORR) of Au NPs/TiO2-NPs-N2 and Au-NPs against glycerol oxidation in basic media was studied. The results indicated that Au NPs/TiO2-NPs-N2 is a promising support material for improving the electrocatalytic activity for acidic and basic oxidation. The electrode made of Au NPs/TiO2-NTs-N2 has steady electrocatalytic activity and may be reused repeatedly. TiO2 NPs and Au NPs/TiO2NPs-N2 showed satisfactory antibacterial activity against some human pathogenic bacteria using the disc diffusion method.

Synthesis of black TiO2 nanotubes decorated biomass-derived spongy carbon as an electrode material for producing deionized water through capacitive deionization technology

The capacitive deionization (CDI) technique is considered a promising eco-friendly desalination method due to its high energy efficiency, ease of operation, and simplistic electrode regeneration capability. Thus, significant research is focused on developing highly efficient electrode materials with high electrochemical stability and salt electro-adsorption capacity (Sc) behavior during operation because these are the governing factors in examining the measured activity of fabricated CDI cells. In this manuscript, we report the synthesis of hydrogenated titanium nanotubes@spongy activated carbon (HTiO2 NTs@SAC) using pyrolysis and hydrothermal processes. The SAC is synthesized by the pyrolysis of spongy loofa in an inert atmosphere and further hydrothermally activating it in an aqueous potassium hydroxide solution. The hydrothermal process activates and enhances the hydrophilicity of SAC. HTiO2 is synthesized electrochemically at 20 V in 0.1 M perchloric acid. Such HTiO2 NTs@SAC configuration can provide excellent pathways to increase ion adsorption and improve the kinetics of charge transfer by enhancing the contact between the electrolyte and electrode at the interface. It is found that HTiO2 NTs@SAC has a specific capacitance (Cs) of 385.7 F g−1 compared with 332.7 F g−1 for SAC. The salt electrosorption capacity (Sc) of HTiO2 NTs@SAC electrode material is found to be 24.90 mg g−1 in 250 μS cm−1 saline solution at 1.2 V, which is much higher than the values obtained for SAC (9.8 mg g−1). HTiO2 NTs@SAC has also shown an antimicrobial effect toward gram-negative bacteria and exhibited good performance in the supercapacitor application, wherein HTiO2 NTs@SAC showed a higher Cs (505.55 F g−1) than SAC (380 F g−1) at 1 A g−1. Thus, we demonstrate that the prepared composite can be used as an energy storage material, an antibacterial material, and a CDI electrode in the CDI technology.

Stability indicating reversed-phase-high-performance liquid chromatography method development and validation for pyridostigmine bromide and sodium benzoate in oral solution.

The present study focuses on the development of a simple, rapid, specific, and stability-indicating HPLC method for the simultaneous analysis of pyridostigmine bromide (PGB) and sodium benzoate (SBN) in oral liquid dosage forms. Analytical techniques should enhance sensitivity and specificity for the estimation of pharmaceutical drug products. Stress studies were conducted under various International Conference on Harmonization (ICH) conditions for evaluation. The further optimized HPLC method was validated in accordance with the current ICH guidelines. Chromatographic separation was accomplished using a mobile phase consisting of a 950:50 v/v ratio of perchloric acid buffer and acetonitrile as mobile phase-A, and 100% acetonitrile as mobile phase-B. The flow rate is 1.0 mL/min, and the injection volume is 20 μL. Detection of components was carried out at 220 nm for PGB and 228 nm for SBN. The validated HPLC method demonstrated high specificity, with linearity ranging between 24 and 72 μg/mL for PGB and 5.2-15.6 μg/mL for SBN. The correlation coefficient for both drugs exceeded 0.999. The method demonstrated high accuracy, exceeding 97%. In stress studies, PGB was found to be sensitive to alkaline stress conditions. The results reveal the successful applicability of the current method for the estimation of PGB and SBN in its marketed formulation, which can be reasonably inferred to assess other formulation systems.

INFLUENCE OF THE POSITIVE ELECTRODE PROPERTIES ON THE ACTIVATION TIME OF THE RESERVE CHEMICAL POWER SOURCES OF THE SYSTEM LEAD – PERCHLORIC ACID – LEAD DIOXIDE

The influence of the positive electrode properties on the activation time of the reserve chemical power sources of the system lead – perchloric acid – lead dioxide has been studied. Coatings of cathodes with lead dioxide obtained under various conditions are characterized by scanning electron spectroscopy, X-ray spectral microanalysis, X-ray photoelectron spectroscopy, standard contact porosimetry. The improvement of the performance characteristics of power sources including the ensuring of a short time of their activation at a low temperature has been shown to be possible with the use of a nanoporous coating of lead dioxide. To estimate the applicability of cathodes for the manufacture of power sources having minimal activation time a diagnostic principle has been used that it based on testing of cathodes by the method of chronopotentiometric measurements during galvanostatic discharge. Pilot industrial samples of small-sized reserve power sources of the mentioned electrochemical system with unprecedented short activation time (less than 30 ms at temperarure –50°С) were manufactured and tested.

Strategy for absolute quantification of phospho‐Tau epitopes in cerebrospinal fluid by mass spectrometry

AbstractBackgroundMass spectrometry is used as reference method for protein quantification by measuring tryptic peptides derived from the target protein relative to a stable isotope‐labeled standard. Existing targeted mass spectrometric methods to measure total tau (tTau) and phosphorylated tau (pTau) species in cerebrospinal fluid (CSF) rely either on immunoaffinity enrichment of the protein or exploit the unusual property of tau being soluble in 2.5% perchloric acid (PA), to precipitate abundant sample proteins. Both strategies, however, carry risk of introducing bias: immunoaffinity enrichment relies on the specificity of the used antibodies, which may not have equal affinity for all of the large number of processed or modified forms of tau, and PA may partially precipitate some tau forms. To address this problem, we have developed an antibody‐ and PA‐free method to measure tau and pTau epitopes in CSF by targeted mass spectrometry.MethodCSF samples (100 µl) from healthy individuals (HC) and Alzheimer’s disease (AD) patients were spiked with stable isotope‐labeled tau peptide standards containing the phospho‐epitopes pTau181, pTau231, pTau217, pTau205, and non‐phosphorylated Tau212‐221, and subjected to tryptic digestion. Desalted samples were fractionated by strong anion‐ and strong cation‐ exchange (SAX and SCX, respectively) solid phase extraction with step‐wise pH elution. The fractions were analyzed by parallel reaction monitoring on a nano‐flow LC‐MS on a Quadrupole‐Orbitrap hybrid mass spectrometer.ResultSeveral tau peptides were detected with both SAX and SCX, including pTau181, pTau217, pTau205, and Tau212‐221. The reproducibility of the new assay was assessed, and its performance was compared with PA‐based sample preparation and immunoassays for tau and pTau in a pilot study of AD patients and controls.ConclusionThe method described here allows for the detection of multiple tau/pTau peptides, while avoiding the need for selective protein isolation methods such as immunoaffinity enrichment or PA precipitation, thereby eliminating bias toward more/less soluble tau species.

The Effect of the Positive Electrode Properties on the Activation Time of the Lead–Perchloric Acid–Lead Dioxide-Based Reserve Chemical Power Sources

The Effect of the Positive Electrode Properties on the Activation Time of the Lead–Perchloric Acid–Lead Dioxide-Based Reserve Chemical Power Sources

Investigation of Physicochemical Characteristics of Lead Dioxide Coatings to Enhance the Performance of Reserve Quickly Activated Chemical Power Sources in the Lead–Perchloric Acid–Lead Dioxide System

The relationship between the discharge characteristics of reserve chemical power sources of the lead–perchloric acid–lead dioxide system and the physicochemical properties of electroplated cathode coatings with lead dioxide, including phase composition and microstructure, has been studied. The study reveals that the discharge characteristics of power sources can be enhanced by employing a two-layer lead dioxide coating consisting of a porous outer layer and a denser inner layer. The findings have been validated through the production and testing of industrial prototypes of pilot miniature reserve power sources, which exhibit improved performance even at low temperatures (activation time, less than 30 ms; discharge capacity, ~200 mA min/cm2; discharge voltage per cell, 1.8–1.2 V at –50°C).

Investigation of Physicochemical Characteristics of Lead Dioxide Coatings to Enhance the Performance of Reserve Quickly Activated Chemical Power Sources in the Lead–Perchloric Acid–Lead Dioxide System

Investigation of Physicochemical Characteristics of Lead Dioxide Coatings to Enhance the Performance of Reserve Quickly Activated Chemical Power Sources in the Lead–Perchloric Acid–Lead Dioxide System

The effects of Al (111) and Al2O3/Al (111) surfaces on the decomposition of ammonium perchlorate: A DFT-D study

Ammonium perchlorate (AP) is a crucial oxidizing agent in composite solid propellants, where aluminum (Al) is used as an additive to increase the energy density of composite solid propellants. The interaction between AP and Al significantly improves the ignition and combustion performance of propellants, but the mechanism of their interactions still lacks essential understanding, especially the interaction between AP and Al, as well as the Al surface containing aluminum oxide (Al2O3). To solve this problem, the adsorption and decomposition processes of AP and its decomposition products such as perchloric acid (HClO4) and ammonia (NH3) on the pure-Al (111) and Al2O3/Al (111) surfaces were studied by using the density functional theory (DFT). The effects of temperature and pressure on the adsorption and reactions were discussed. AP tends to adsorb on the pure-Al (111) surface with O-termination, while under the influence of Al2O3, AP is more inclined to adsorb on the surface of Al2O3/Al (111). At the low-temperature stage, the Al2O3 molecules on the surface of Al (111) promote the disengagement H of AP decomposition and the adsorption and decomposition of NH3, while at the high-temperature stage, the pure Al surface is more conducive to the AP disengagement H and NH3 decomposition. The increase in the pressure is in favor of NH3 adsorption, but the effect gradually decreases. HClO4 cannot adsorb on the pure-Al (111) and AP (001) surfaces, but it can adsorb on the surface of Al2O3/Al (111). In the gas phase, the decomposition of HClO4 priors to NH3. At the high temperature and pressure, the pure-Al (111) surface can contribute significantly to the adsorption and activation of NH3. The findings are very valuable for regulating the combustion of solid propellants.

Stability indicating high‐performance liquid chromatography method for determining doxycycline hyclate and related substances in their various dosage forms: Utilizing Six Sigma tools, uniformity testing, and in‐vitro dissolution approaches

AbstractDoxycycline hyclate (DOXH) is very important to treat acne and prevent infections caused by bacteria, so quantifying doxycycline hyclate and its related substances is crucial. In this work, All analytes of doxycycline and its related substances, including methacycline, 4‐epi doxycycline, 6‐epi doxycycline, and 2‐acetyl‐2‐carbamoyl doxycycline, were successfully separated at low concentrations in a single run utilizing the suggested isocratic high‐performance liquid chromatography method with a mobile phase comprising water:acetonitrile:perchloric acid (75:25:0.2, v/v), Phenomenex Luna C18 column (50 × 4.6 mm, 3 μm i.d.) maintained at 30°C with a flow rate of 0.7 mL/min, injection volume of 25 μL, and photodiode array detector at 269 nm. DOXH and its related substances were linear in the range of 0.25–50, 0.1–30, 0.2–35, 0.5–50, and 0.6–20 μg/mL, respectively, with correlation coefficients greater than 0.999 and good accuracy results between 98% and 102%. The method has been successfully used to determine the drug's comparative study in both generic and reference products, demonstrating the similarity between the two products. According to the International Council for Harmonization requirements, the proposed approach was validated. Additionally, the technique has effectively studied in vitro dissolution, Six Sigma, and content uniformity.

Leaching studies of magnesite using perchloric acid thermochemical and electrochemical treatment of magnesium chloride

Leaching studies of magnesite using perchloric acid thermochemical and electrochemical treatment of magnesium chloride

A controllable fabrication strategy of anodic oxides film with dense, nano-porous and open-top ordered porous arrays morphology on 304 stainless steel in fluoride-based ethylene glycol electrolyte

A facile anodizing strategy without using perchloric acid was reported in this work to controllably produce three different types of self-organized structure anodic oxides films with dense, nano-porous and open-top ordered porous arrays structure morphology. These oxides were developed on 304 austenitic stainless steel (SS) substrate in fluoride-based ethylene glycol electrolyte by simply regulating the H2O concentration in the electrolyte and anodizing voltages. From our analysis, it was found that the above-mentioned anodizing parameters significantly affect the morphologies of the anodic oxides film rather than the chemical composition. The chemical compositions of the different types of films were α-Fe2O3 and Cr2O3 or (FexCr1-x)2O3 composite oxides. Moreover, the higher (70 V), middle (50 V), and lower voltages (30 V) were respectively suitable for the preparation of the dense, nano-porous, and open-top ordered porous arrays morphology structure anodic oxides film due to the different anodized film formation rate, respectively. Finally, a plausible formation-dissolution mechanism was provided by considering the dissolution effect with the assistance of the oxygen evolution derived from H2O, which is favourable to form the sparser anodized film on the SS substrate. In addition, the anodizing parameters selected principle for the corresponding anodic oxides layers with different morphologies onto the SS substrate. The controllable fabrication strategy of the various film will greatly broaden the application of the SS substrate in both anti-corrosion and decoration fields.

N-methyl ortho-bipyridines as a new member of metal-free electrocatalysts for hydrogen evolution reaction (HER): The influence of the substituent on a heteroatom on the pathway (mechanism) HER

Using the method of cyclic voltammetry (CV), the electrocatalytic activity in the hydrogen evolution reaction (HER) in the presence of perchloric acid and N-methyl-2,2′-bipyridinium and N,N′-dimethyl-2,2′-bipyridinium iodides was studied. Conducting preparative electrolysis with simultaneous gas chromatography showed that in both cases the catalytic process is realized, however, in the case of N,N′-dimethyl-2,2′-bipyridinium iodide, the efficiency of the electrocatalytic process is much higher than in the case of N-methyl-2,2′-bipyridinium iodide. It has been shown for the first time the possibility to selectively engage different catalytic centers to hydrogen evolution reaction by varying the potential or the concentration of the acid. So, in case of N,N′-dimethyl-2,2′-bipyridinium iodide at low acid concentrations the catalytic process proceeds according to a homogeneous mechanism in parallel on both catalytic centers. At high acid concentrations on the CV two new waves appear which associated with the formation of additional pathways for the generating of molecular hydrogen - in the second wave it is realized according to the intramolecular mechanism, while in the third wave it is realized according to the heterogeneous mechanism. In the case of N-methyl-2,2′-bipyridinium iodide, one catalytic center can be selectively involved or both centers can “work” in parallel according to a different mechanism by varying the potential of the electrocatalytic process. It is important to note that the discovered phenomenon has not been previously described in the literature.

HEAVY METALS QUANTIFICATION AND CORRELATIVE CARCINOGENIC-RISKS EVALUATION IN SELECTED ENERGY DRINKS SOLD IN BAYELSA STATE USING ATOMIC ABSORPTION SPECTROSCOPIC TECHNIQUE

Objective: The study aimed to quantify the concentrations and carcinogenic-related health risks assessment of some heavy metals in selected energy drinks frequently utilized in Bayelsa State, Nigeria. Methods: Eleven energy drinks samples were purchased from the general markets in Amassoma and Yenagoa, Bayelsa State, Nigeria, and were labeled D1–D11. The samples were digested using 10 ml of nitric acid at 120-150 ℃, and 2 ml of Perchloric acid was added after attaining room temperature, it was digested further until a clear solution was obtained, then made up to 25 ml with distilled water. The concentration of lead, cadmium, iron, and zinc were determined and quantified using Atomic Absorption Spectrophotometry (AAS), and the health-associated risks of these metals were evaluated using the standard Target Health Quotient (THQ). Results: The EDI (Estimated Daily Intake) of lead (Pd), Cadmium (Cd), iron (Fe), and zinc (Zn) was 0.130, 0.001, 0.726, and 0.193 mg/l, respectively, all were within the World Health Organization (WHO)-acceptable range. The Chronic Daily Intake (CDI) of Pd, Cd, Fe, and Zn was obtained as 0.001 to 0.010, 5.7 x 10-5, 0.001 to 0.050, and 0.0001 to 0.010 mg/l respectively. Conclusion: THQ for all metals analyzed was<1, the WHO acceptable limit. All the heavy metals were within acceptable THQ limits, thus posing no carcinogenic health potential risks on long-term consumption.