Reaction Phenomena Research Articles

Interventions for anticipatory traumatic reaction: a pilot study

ABSTRACT Objective This study assessed the effectiveness of interventions intended to mitigate anticipatory traumatic reaction, a form of future-focused distress occurring in response to threat-related media reports and discussions. Method A stratified sample of 512 Australian adults (260 women and 252 men; mean age = 46.80, SD = 16.62) completed measures of anticipatory traumatic reaction, and positive and negative affect. Participants then viewed a stimulus video containing a series of terrorism and crime reports, and were randomly assigned to one of seven conditions. The conditions consisted of six brief online interventions, based on standard psychological treatments for anxiety and mood disorders, and one control condition. Results A cognitive intervention to address probability neglect (p < .001) and a mindfulness intervention (p = .036) both significantly attenuated momentary anticipatory traumatic reaction. Conclusions This research provides information leading to better understanding the phenomenon of anticipatory traumatic reaction and pilot results related to reducing levels of distress for affected individuals.

Ռուս-ուկրաինական թնջուկ. ինչպե՞ս է դիրքավորվում աշխարհը/Complex Problem of Russian-Ukrainian Relations։ What Position do the Countries of the World Take?

Any political, military or economic event taking place in the post-COVID world can radically change our understanding, both in terms of identifying the origins of this or that event, and in terms of assessing its motives and predicting the final result. The challenge of the Covid pandemic revealed common gaps in anti-crisis management in force majeure situations, and as a result of a chaotic information collapse, the phenomenon of an aggressive reaction of some people to the performance of seemingly primitive domestic and disciplinary duties was revealed. In other words, two “armies” of believers and non-believers formed around the same phenomenon. The main reason for this disagreement was the controversial information "terrorism", which developed a certain negative attitude towards all the planned mandatory measures that were carried out in order to ensure a safe, quality life and human health. And now, not yet fully freed from the nightmare of covid fears, the world in the form of the Russian-Ukrainian military conflict is plunging into a new long nightmare. In this case, unlike the previous one, there is no common joint decision regarding this event, even in those associations or organizations whose unanimous opinion was effectively used as the main trump card in such "force majeure" or crisis situations. Any military conflict is a catastrophe with a huge amount of human and material losses. Regardless of their scale, they all have in common a high probability of repetition, as the role of winner and loser becomes very relative over a long historical time. Proof of this are the two world wars of the 20th century, when the winners changed, and active “hot” wars were followed by “cold” phases, the logical outcome of which was to return to the “hot” phase at the right time, with almost the same players. However, in this periodic chain, due to the logic of the “cold” phase, positions and roles could change and it is possible that those who previously contributed on one front would find themselves in opposite “trenches”. Armenia, which currently has an unresolved Artsakh issue, unfriendly relations with at least two of its four neighboring countries, and unresolved border issues, has also found itself in a similar trap. Realizing the impossibility of a final solution to the conflict by military means, as well as understanding the consequences of our position concerning the Russian-Ukrainian military conflict, we need to quickly conduct the most accurate analysis of the external and internal situation by developing possible outcome scenarios. Without this, it is impossible to get out of the complex process of changing the world order, having received only “light scratches”. In order to draw up a "road map" and a schedule of our further actions, first of all, it is necessary to have a clear idea of how the countries and regions of the world are located in relation to the Russian-Ukrainian conflict and what the motives and arguments for this position are. It should also be taken into account that the situations that arise in the future will not only be vital for Armenia in their essence, but will also contain a pronounced existential component.

Bioconvection Mangnetohydrodynamic Tangent Hyperbolic Nanofluid Flow with Quartic Chemical Reaction Past a Paraboloid Surface

In this numerical study, the effect of quartic autocatalysis type of chemical reaction, buoyancy force and thermal radiation phenomenon and magnetic effect on tangent hyperbolic nanofluid past an upper horizontal surface of a paraboloid has been studied. By considering the Buongiorno model approach, a diffusion of unequal coefficients in the presence of gyrotactic microorganism is discussed. Implementation of microorganism's idea is used to stabilize the nanoparticles through bioconvection. The modeled PDEs of the problems are converted into nonlinear ODEs with the assistant of the similarity transformations. To tackle nonlinear ODEs, MATLAB package bvp4c is used. In addition, a hallmark of the Matlab code with the reported results in the literature is achieved by benchmarking. The variations in motion, concentration, temperature, and motile density due to sundry parameters have been analyzed in-depth via graphs. Our analysis shows that the density profile of motile of microorganism is hiked with an increment in the bioconvection Rayleigh number but decreases for higher thermal Grashof number.

Doped 2D SnS materials derived from liquid metal-solution for tunable optoelectronic devices.

Gas-liquid reaction phenomena on liquid-metal solvents can be used to form intriguing 2D materials with large lateral dimensions, where the free energies of formation determine the final product. A vast selection of elements can be incorporated into the liquid metal-based nanostructures, offering a versatile platform for fabricating novel optoelectronic devices. While conventional doping techniques of semiconductors present several challenges for 2D materials. Liquid metals provide a facile route for obtaining doped 2D semiconductors. In this work, we successfully demonstrate that the doping of 2D SnS can be realized in a glove box containing a diluted H2S gas. Low melting point elements such as Bi and In are alloyed with base liquid Sn in varying concentrations, resulting in the doping of 2D SnS layers incorporating Bi and In sulphides. Optoelectronic properties for photodetectors and piezoelectronics can be fine-tuned through the controlled introduction of selective migration doping. The structural modification of 2D SnS results in a 22.6% enhancement of the d11 piezoelectric coefficient. In addition, photodetector response times have increased by several orders of magnitude. Doping methods using liquid metals have significantly changed the photodiode and piezoelectric device performances, providing a powerful approach to tune optoelectronic device outputs.

Synthesis and validation of polystyrene-based polyethylenimine composite for Cr(VI) removal from aqueous solution: Performance and mechanism

With increasing groundwater and surface water contamination due to improper discharge of chromium-laden wastewaters, it is compelling to synthesize a material that can selectively remove Cr(VI) from the impaired water at neutral or near-neutral pH. In this study, various composites were synthesized through chemical grafting of polyethylenimine (PEI) polymer on the surface of INDION PA 800 polystyrene beads by varying the PEI loading and glutaraldehyde (GA) crosslinking for Cr(VI) removal. The adsorbent called PS-7 with 16% PEI and 2.5% GA crosslinking performed best, demonstrating Cr(VI) removal greater than 99% even at pH 9. The adsorbent showed significant trace Cr(VI) removal from the impaired solution containing competing anions at 500 times the concentration of Cr(VI) at neutral pH. Further, 1.0 g/L adsorbent showed 100% Cr(VI) removal from a solution containing 5 mg/L Cr(VI) at pH 7 and 9. PS-7 showed significant adsorption capacity of 355.26 and 143.6 mg/g for fixed-bed column runs at influent pH 3 and 5, respectively. An insightful investigation revealed that the use of hydrophobic matrix for PEI immobilization played an important role in Cr(VI) removal at neutral pH, as opposed to the other reported PEI-based adsorbents with hydrophilic matrix which were capable of removing chromate anions at acidic pH only. The phenomenon of redox reaction occurring in the adsorbent was validated by X-ray photoelectron spectroscopy, where Cr(VI) was reduced to Cr(III) with the help of electron-donating NH2 groups and the adsorbent got oxidized. Thus, PS-7 adsorbent holds immense potential for treating real-life Cr(VI)-contaminated waters.

Non-Newtonian Cross fluid flow through a porous medium with regard to the effect of chemical reaction and thermal stratification phenomenon

A comprehensive study encompassing a general development and a presentation of results for the influence of the chemical reaction on the laminar Cross fluid flow and heat mass transfer is made here. The motion of the fluid is assumed due to the stratified stretching sheet which embedded in a porous medium. Some of important characteristics of the fluid such as the variable thermal conductivity and its dependence on the temperature field are mentioned. Accordingly, some account of the possible effects of heat generation on heat mass transfer in fluid flows is given. Numerical treatments have been introduced for the resulting coupled ordinary differential equations. Then, the results of the variation in the velocity profile, the temperature profile and the concentration profile due to porous parameter, thermal conductivity parameter, heat generation parameter, thermal stratification parameter and chemical reaction parameter are presented graphically. At the proposed physical conditions for the problem, the Sherwood number, the Nusselt number or the temperature gradient and the local skin friction coefficient were measured. It is interesting to observe that, both the solutal and the thermal stratification phenomena plays a dominant role in the mechanism of heat and mass transfer. Also, regarding the warming factors within the thermal boundary layer, both Darcy parameter and heat generation parameter have been proposed which are of special interest in heat transfer problems. Finally, the results pointed out the efficiency of the proposed numerical method, where it gives a good representation describing the mechanism of the flow, heat and mass transfer.

Machine learning based analysis of reaction phenomena in catalytic lignin depolymerization

Heterogeneously catalyzed lignin solvolysis opens the possibility of transforming low value biomass into high value, useful aromatic chemicals, however, its reaction behavior is poorly understood due to the many possible interactions between reaction parameters. In this study, a novel predictive model for bio-oil yield, char yield and reaction time is developed using Random Forest (RF) regression method using data available from the literature to study the impact of surface properties of the catalyst and the weight averaged molecular weight of the lignin (Mw) used in the reaction. The models achieved a coefficient of determination (R2) score of 0.9062, 0.9428 and 0.8327, respectively, and feature importance for each case was explained and tied to studies that provide a mechanistic explanation for the performance of the model. Surface properties and lignin Mw showed no importance to the prediction of bio-oil yield and average pore diameter contributed 3% of feature importance to reaction time.

Transient reaction phenomena of sorption-enhanced steam methane reforming in a fixed-bed reactor

The transient chemical reaction phenomena of the sorption-enhanced steam methane reforming (SE-SMR) by using Ni/Al2O3 catalyst and CaO sorbent in a tubular fixed-bed reactor were numerically investigated by an experimentally verified unsteady 2D model. Four chemical reactions are involved in SE-SMR including steam reforming (SR), water gas shift (WGS), global steam reforming (GSR), and CO2 sorption. The reaction process in time is divided into period 1, transient period, and period 2. The high-purity H2 is produced in period 1 which is defined as the outlet molar fractions of H2 ≥ 90% and CO ≤ 1% (dry basis) in this work. In the first half of period 1, the endothermic reaction rates of SR and GSR are dominant in the entrance region of catalyst/sorbent bed. The WGS and CO2 sorption reactions are triggered by SR and GSR reactions. The heat transfer from the wall plays an important role. Higher CaO conversion, temperature, and reaction rates appear first near the wall region, then they gradually expand to the central region.In the second half of period 1, a sharp wave-shaped curve of strong CO2 sorption reaction occurred in downstream becomes dominant and it moves to downstream almost at a constant speed, as time progresses. The peak value of the CO2 sorption reaction is more than twice larger than that of SR or WGS. The SR and WGS reaction rates are significantly enhanced by CO2 sorption reaction. The great sorption, WGS, and SR reactions result in a high-purity H2 production with the outlet molar fractions of 95.8% H2, 0.998% CO, and 0.73% CO2 at the end of period 1, based on the parameters used in this work such as reactor temperature of 600 °C. The maximum CaO conversion is about 76% in end of period 1 and the average CaO conversion in the reactor is 51%. The 2D distributions of CaO conversion, temperature, and reaction rates are also presented and discussed.

Analysis of Newtonian heating and higher-order chemical reaction on a Maxwell nanofluid in a rotating frame with gyrotactic microorganisms and variable heat source/sink

The goal of this study is to investigate the rotating Maxwell nanoliquid flow incorporating gyrotactic microbes with Newtonian heating and irregular heat source sink. The motion of the flow is induced due to linearly unidirectional elongated surface. The uniqueness of the flow is enhanced by the inclusion of additional phenomenon of higher order chemical reaction incorporated with Darcy Forchheimer flow, Fourier and Fick law. Numerical solution of the formulated problem is developed via bvp4c function in MATLAB. The influence of the embroiled parameters on the flow distribution is demonstrated through various graphs and tables. It is noticed that fluid velocity declines on incrementing the rotation parameter. An upsurge in thermal field is portrayed on augmenting the Newtonian heating. Comparative analysis of the results of the proposed model with previous published research is included which confirms the validity of the current model.

Impacts of activation energy and binary chemical reaction on MHD flow of Williamson nanofluid in Darcy–Forchheimer porous medium: a case of expanding sheet of variable thickness

An expanding sheet problem is more relevant when the thickness of the sheet is variable and it bears frequent applications in polymer press, paper production, metallic plate cooling, etc. On the other hand, activation energy is an important phenomenon of chemical reaction in flow dynamics of Newtonian and non-Newtonian fluids. The activation energy and chemical reaction have vital applications in food preparing, the mechanism of water and oil emulsions, chemical engineering, and more. So in this project, the impacts of activation energy and binary chemical reaction on MHD two-dimensional boundary layer flow of Williamson nanofluid on an expanding surface of variable thickness embedded in Darcy–Forchheimer porous medium are investigated. Using suitable transformations, the governing equations are transformed into a set of non-linear ordinary differential equations (ODEs). Later, numerical solutions have been achieved by well-known MATLAB inbuilt function ‘bvp4c’. Several vital results are explored for variations of involved physical parameters and those are presented in graphical and tabular modes. The achieved results suggest that when wall thickness parameter increases, there is a contrast in behaviors of velocity, temperature and nanoparticle concentration if there is a condition that the shape parameter is greater than or less than unity. For the former case, the above flow properties reduce with wall thickness parameter, whereas, for the latter case, those are showing significant growth. The Brownian motion of nanoparticles causes an increase in temperature and a reduction in nanoparticle concentration, whereas due to thermophoretic force, both temperature and nanoparticle concentration rise. Due to the presence of activation energy in chemical reaction, the nanoparticle concentration enhances, while, temperature decreases(increases) near(away from) the sheet. With increasing reaction rate parameters, nanoparticle concentration diminishes, but temperature increases near the sheet. The surface drag force decreases with Williamson fluid parameter, while it increases with the magnetic parameter, inverse Darcy number, and Forchheimer parameter. On the other hand, the surface heat flux and surface mass flux are decreasing functions of Williamson fluid parameter, magnetic parameter, inverse Darcy number, and Forchheimer parameter. It also reveals that surface heat flux reduces with increasing reaction rate parameters, whereas surface mass flux increases. Finally, for the growth of activation energy parameter, initially surface heat flux rises and surface mass flux declines, but for its larger values, the quantities turn out to be constants. Also, the surface heat and mass fluxes are decreasing functions of thermophoresis parameter.

Using Computational Chemistry to Improve Students’ Multidimensional Understanding of Complex Electrophilic Aromatic Substitution Reactions: Further Analysis of the Solvent Effect, Temperature Influence, and Kinetic Behaviors

Student-centered teaching has become increasingly common in higher education as researchers have demonstrated its efficacy in recent decades. Herein, we hope to establish an efficient problem-based learning (PBL) method, which can help upper-division students learn organic chemistry content by combining teaching materials, experimental literature, and computational methods in a self-directed way, systematically and deeply. We aim to cultivate the critical-thinking skills of students and to expand modern research methods to analyze, predict, and understand organic chemical processes. On the basis of such goals and ideas, we take the practical Friedel–Crafts alkylation reaction as a model reaction. We focus on two key points, the pre-equilibrium and the rate-determining step (RDS). In combination with the textbook knowledge and DFT calculation method, we attempt to promote the upper-division students to further discuss and understand reaction details, including kinetic-controlled reactions, the Hammond–Leffler postulate, and the Curtin–Hammett principle, etc. Following this approach, we achieve our goals to discuss the Friedel–Crafts alkylation reaction and provide juniors with a deep understanding of the carbon–carbon bond formation reaction. Furthermore, students initially master the DFT calculation method and make a direct connection between experimental observations and computational results. This approach activates students’ study interests to further use core ideas of structures and bonding to rationalize complex chemical reaction phenomena for their future learning career.

3D printing of gelatin/chitosan biodegradable hybrid hydrogel: Critical issues due to the crosslinking reaction, degradation phenomena and process parameters

Hydrogel materials are being investigated for application as scaffolds in tissue engineering owing to their many advantages, such as high water content, softness and flexibility similar to many soft tissues, tuneable physical, chemical, and biological properties, excellent biocompatibility and biodegradability, and extensive framework for cell proliferation and survival. During the past decade, because of the great versatility offered in terms of processing approach, material selection, and customization, 3D printing has become a leading technology used to fabricate hydrogel scaffolds. Furthermore, high reproducibility and unparalleled control over structural and compositional characteristics make additive manufacturing the preferred technology for the fabrication of biodegradable hydrogel scaffolds. However, the production time could become critical in relation to any crosslinking reactions and degradation that may occur in the hydrogel and make the printing process unstable. In this study an analysis of the critical issues due to the crosslinking reaction and degradation phenomena have been executed following a statistical approach. In particular, three different experimental campaign demonstrate how the printing process became instable due to the mentioned phenomena. Finally, a procedure was developed to print gelatine-based biocompatible hydrogels with chitosan and functionalized polyethylene glycol as a cross linker (G-PEG-CH). In order to reach the printing temperature, the hydrogel mixture was initially stored in the refrigerator at 4°C for 12 h, followed by a 10 min incubation in warm water at 40°C. Based on this procedure, a filament strand of 950 μm with a standard deviation in the range of 20% was obtained by imposing a printing pressure of 1 bar and a printing speed of 100 mm/s at a temperature of 28 °C.

Prolonged SARS‐Cov‐2 shedding with rapid IgG antibody decay in a COVID‐19 patient: A case report

BackgroundThe coronavirus disease 2019 (COVID‐19) epidemic is still spreading rapidly around the world. Recent cases with prolonged severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) RNA detection have been successively reported, and the phenomenon of false‐negative real‐time polymerase chain reaction (RT‐PCR) results of SARS‐CoV‐2 RNA or “repositive” was also described in COVID‐19 patients.MethodsWe report a 69‐year‐old female patient with hypertension, suspected lung tumor, and previous history of total hysterectomy for hysteromyoma who presented with moderate COVID‐19 symptoms and was positive for SARS‐CoV‐2 RNA by RT‐PCR when she traveled from the USA to China.ResultsThe patient required second and third re‐hospitalizations due to “repositive” SARS‐CoV‐2 throat swab test results during post‐charge solitary isolation and observation, and serum SARS‐CoV‐2‐IgG decayed rapidly before disappearing on illness Day 139 when the throat swab was still positive. The virus shedding lasted for at least 146 days (the last positive throat swab test result was on illness Day 146, and the first true‐negative test result was on illness Day 151) since her initial positive test.ConclusionProlonged SARS‐CoV‐2 RNA viral shedding is prone to occur in an immunocompromised host, wherein changes in the host immune status can lead to repeated positive SARS‐CoV‐2 detection. Moreover, the SARS‐CoV‐2‐IgG may decrease rapidly and disappear before virus removal, indicating there may be certain limitations on the protective effect of the SARS‐CoV‐2 antibody, which deserves clinical attention.

High temperature reaction of multiple eutectic-component system: The case of solid metallic Zr and molten stainless steel-B4C

The eutectic melting, one of the fundamental phenomena in high temperature reactions involving liquid phases, is a primitive but important subject for both scientific and industrial fields associated with metallurgy. The present study aims at revealing the formation and reaction mechanisms of the multiple eutectic-component system consisting of solid metallic Zr and molten stainless steel-boron carbide (SS-B4C) by combining multiple analytical methods (i.e. powder X-ray diffraction (PXRD), scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM/EDS), and dynamic secondary ion mass spectrometry (D-SIMS)) with thermodynamical consideration. The results indicate that the solidified Zr-SS-B4C mixture is composed of major phases of (Fe,Cr)2Zr, (Fe,Cr,Ni)2Zr, (Ni,Fe)Zr2, ZrB2, and a minor phase of ZrC. The results also reveal that the eutectic melting between solid metallic Zr and molten SS-B4C can be described as the combination of diffusion kinetics and thermodynamic stability. That is, the initial formation of ZrC and ZrB2 layers at the reaction interface significantly retards the diffusion of other SS-B4C components (i.e. Cr, Fe, and Ni) into solid metallic Zr.

Numerical Analysis of the Effect of Trapezoidal Baffles Inside Fuel and Air Channels on the Performance of a Planar-Type Solid Oxide Fuel Cell

Abstract This paper investigates the effect of trapezoidal baffles inside a planar-type solid oxide fuel cell. To achieve the objective, four cases are proposed: (1) simple planar geometry as a base case, (2) trapezoidal baffles inside the fuel channel, (3) trapezoidal baffles inside the air channel, and (4) trapezoidal baffles in both fuel and air channels. The height of the trapezoidal baffles inside the channels of the solid oxide fuel cell increases along the direction of the fluid flow. The numerical investigation is based on a three-dimensional computational fluid dynamics (CFD) model that takes into account the phenomenon of mass transfer, heat transfer, species transport, and electrochemical reactions. A detailed comparison of the performance between the four cases of the fuel cell is provided in terms of power density, fluid flow, species concentration, temperature distributions, and electric fields at a variable current density and a fixed power density of 3000 W/m2. The results show that the power density, the velocity, the availability of the hydrogen and oxygen species on the electrodes-electrolyte interfaces increases for case 2, case 3, and case 4, respectively, in comparison to case 1. Finally, the average temperature of the electrode–electrolyte interface is reduced with the baffles, and it is concluded that the configuration with baffles inside the air channel (case 3) shows better results in terms of the increment of the power density and the decrement of the average temperature.

The effect of the secondary reactions on volatile composition during the pyrolysis treatment of scrap tires

ABSTRACT The phenomenon of the secondary reactions of volatiles prevails during the pyrolysis process of scrap tires, but less is known about the influence of volatiles’ residence time and temperature on the pyrolytic oil compositions. Experiments on the secondary reactions caused by residence time and temperature of volatiles were carried out on a lab-scale fixed bed reactor. The regularity of the secondary reactions was presented in detail according to the distribution of liquid and gaseous pyrolytic products. Considering the inadequacy of lab-to-industry research, experiments were further carried out on a pilot-scale auger reactor. The results of the pilot-scale system were corresponding well to the regularity obtained in lab-scale experiment, demonstrating the universality of the regularity in this work. At in situ pyrolysis condition without any secondary reactions, limonene content reached up to 46.24% while a high yield of BTEX (50.55%) was obtained at 700℃/60 s. A remarkable increase of methane and ethane was observed at 700℃/60 s, reaching 0.058 and 0.040 g·(g scrap tire)−1, respectively. This paper provided a novel strategy to selectively produce target products in a simple and economical method. The results were of great significance for guiding the optimisation of pyrolysis parameters in industrial equipment to obtain desired valuable products.

(Invited) Understanding Multi-Component Transport and Reaction Phenomena in Bipolar Membranes Used for Electrosynthesis

Bipolar membranes (BPMs), which have long seen usage in electrodialysis reactors for the generation of acid and base, have recently demonstrated potential to become critical components in electrochemical synthesis devices. Because they can operate under large pH gradients, BPMs enable favorable environments for electrocatalysis at the individual electrodes. Critical to the implementation of BPMs in these devices is understanding the kinetics of water dissociation that occurs within the BPM junction as well as the co- and counter-ion crossover through the BPM, which both present significant obstacles to developing efficient and stable BPM-devices for electrosynthesis applications. Prior work has modeled ion transport in bipolar membranes in neutral salt solutions for electrodialysis. However, no model exists for the BPM under the harsh applied pH gradients that would be present in electrosynthesis, and there is significant need to explore the effects of the internal hydration on the lifetime and performance of BPMs in such environments. Additionally, a mechanistic understanding of water dissociation catalysis will be required to develop interfacial catalysts that enable the high current density operation required for scalable electrosynthesis of fuels.In this talk, we discuss modeling methodologies and physics inherent in BPMs and present our recent model of ion transport and water dissociation catalysis in BPMs across the pH scale. Specifically, we simulate multi-ion transport for a BPM with various electrolyte combinations on each side of the membrane, demonstrating the significance of co- and counter-ion crossover in BPMs operating under harsh pH gradients. We then investigate effects caused by hydration gradients that occur due to internal ion-exchange and examine potential methods for improving performance and mitigating crossover. Finally, we examine the impact of the interfacial water dissociation catalyst and perform sensitivity analysis on the key properties (catalyst point of zero charge and pKa) that dictate catalyst performance. These results provide information that is critical to developing a comprehensive understanding of multi-component phenomena in BPMs and to informing the design and implementation of BPMs in next-generation devices for the numerous electrosynthesis chemistries that benefit from operation under an applied pH gradient.

(Keynote) Clustering, Oscillations and Chaos in Electrochemical Many Particle Systems with Coexisting States: From CO Oxidation on Pt to Insertion Batteries

Bistability, i.e. the coexistence of different states at identical external parameters, is a frequently encountered phenomenon in electrode reactions. If the reactions occur on individual, i.e. spatially separated, catalytically active areas that are all electrically connected, each individual active area can be considered as a bistable component, and the entire ensemble of all active areas as a many particle system of such interconnected bistable components. Examples range from (micro-)electrode arrays, where each of a usually moderate number of individual electrodes constitutes the bistable components, to insertion battery cathodes, where each of the billions of nano-particulate storage particles can be considered a bistable component.In this talk, we will demonstrate that despite of their completely different chemical nature, from a dynamic point of view, all these systems can be treated mathematically under a common framework. We will start by introducing the general mathematical description and compile key results that can be derived [1]: (1) All steady states are composed of one, two or three cluster states, i.e. each of the individual components takes on one of the three values which correspond to the three steady states of the individual bistable component at the corresponding common value of the external voltage. (2) Stable steady states possess at most one electrode on the intermediate, autocatalytic branch. As a consequence, the electrodes transition sequentially from one stable state to the other one as the current density is increased. This sequential activation is a generalization of the mosaic instability described in phase transition systems. (3) Ensembles of globally coupled bistable components might exhibit oscillations. We will derive necessary condition of when the many particle system might become oscillatory and illustrate this condition with an intuitive LC analogue.In the second part of the talk we will apply our general theory to two prominent examples. We will start with the CO oxidation on an array of Pt micro-electrodes, where experiments showed collective oscillations [2,3]. For this system, the necessary condition for a Hopf bifurcation to occur translates to the condition that components in two different groups (or, equivalently two of the three steady states of the bistable elements) have different slopes in either of the two dependences: the change of the coverage with potential at constant CO coverage, or in the change of the current with CO coverage at constant potential. While the first derivative is always positive, the current increases with coverage in the active state (where the coverage is low), but decreases in the passive (CO covered state) or the intermediate states which possess relatively high coverages. The existence of stable oscillations is indeed also observed in simulations. Besides oscillations, this system shows also period doubling cascades and chaos.Our second example involves Li insertion batteries. Here, the chemical potential of each storage nanoparticle exhibits a non-monotonic characteristic as a function of the degree of charging [4]. Hence, the two stable states of a bistable component can be identified with charged and discharged nanoparticle of the insertion material, and a battery under charging / discharging conditions can be classified as a bistable many component system. During charging / discharging with a constant current oscillations of the potential have been reported [5], whose origin has not yet unambiguously been identified. We present a simplified model of the dynamics of the Li ion batteries and again apply our criterion for a Hopf bifurcation to the model. In this case, the necessary condition is not fulfilled so that the origin of the observed oscillations remains in the dark.[1] M. Salman, Chr. Bick and K. Krischer, Phys. Rev. Research 2, 043125 (2020)[2] D. Alfonso Crespo-Yapur, Antoine Bonnefont, Rolf Schuster, Katharina Krischer, and Elena R. Savinova, ChemPhysChem 14, 1117 (2013).[3] S. Bozdech, Y. Biecher, E. R. Savinova, R. Schuster, K. Krischer, and A. Bonnefont, Chaos 28, 045113 (2018).[4] W. Dreyer, J. Jamnik, C. Guhlke, R. Huth, J. Moskon, M. Gaberscek, Nat Mater. 9, 448 (2010).[5] D. Li, Y. Sun, Zh. Zang, L. Gu, Z. Chen, H. Zhou, Joule 2, 1265 (2018)

Enabling Real-Time Quantification of Electrochemical Desorptionphenomena with Sub-Monolayer Sensitivity

Across many scientific and industrial fields, it is a challenge to analyze chemical reaction products with high sensitivity and fast time-response. This is especially true in systems related to electrochemical energy conversion and storage, such as batteries and fuel cells, where accurate monitoring of fast and transient reaction phenomena often reveals key insights.Here, we present a unique analysis instrument using a microchip-based inlet system to couple a mass spectrometer directly to any liquid test environment, aqueous or non-aqueous, and exhibits a sensitivity up to 2-3 orders of magnitude than conventional differential electrochemical mass spectrometry (DEMS).(1–3) The instrument allows to measure the evolution of volatile products and consumption of reactants at electrode surfaces. Due to its extraordinary sensitivity, the system can measure all the individual volatile molecules desorbing from an electrode surface during a single electrochemical turnover. Product formation can be measured from total Faradaic currents of 1 mA all the way down to 200 nA, corresponding to approximately 0.2% of a monolayer (ML) desorbing from the electrode surface in 1s. These features enable time-resolved, fully quantitative measurements of transient phenomena during electrochemistry, providing fundamental insight in the electrochemical reaction mechanisms. Furthermore, an accurately calibrated on-chip gas system allows rapid gas switching between different gases, both inert and reactive. Due to the near-instantaneous equilibration between gas and electrolyte, the transient response of electrodes to rapid gas exposure changes can be measured.As direct evidence of the ultrahigh sensitivity, i n situ quantification the anodic desorption of less than ~1% of a ML of hydrogen on a Cu electrode in alkaline electrolyte (Fig. 1) is shown.(4) Finally, several examples of quantitative electrochemical measurements will be presented, including lattice oxygen contribution during OER on NiFeOxHy,(2) and hydrocarbon oxidation of propene on palladium. (3, 5)Fig.1 H2 desorption on Cu(pc) in 0.1 M KOH. (4) D. B. Trimarco et al., Electrochim. Acta. 268, 520–530 (2018).C. Roy et al., Nat. Catal. 1, 820–829 (2018).A. Winiwarter et al., Energy Environ. Sci. 12, 1055–1067 (2019).S. B. Scott et al., Catal. Sci. Technol. (2020).A. Winiwarter et al., ChemElectroChem, in press. Figure 1

Design of non-autonomous pH oscillators and the existence of chemical beat phenomenon in a neutralization reaction

The beat in physical systems is a transparent and well-understood phenomenon. It may occur in forced oscillatory systems and as a result of the interference of two waves of slightly different frequencies. However, in chemical systems, the realization of the latter type of the beat phenomenon has been lacking. Here we show that a periodic titration of acid and alkaline solutions with each other using programmable syringe pumps in a continuous stirred-tank reactor exhibits the beat phenomenon in the temporal pH oscillation pattern if the time periods of sinusoidal inflow rates of the reagents are slightly different. Interestingly, the frequency of the chemical beat pattern follows the well-known relationship from physics, namely the frequency of the beat is equal to the absolute value of the difference of the two wave frequencies. Based on our strategy, we can design and engineer non-autonomous pH oscillatory systems, in which the characteristics of the temporal oscillations (amplitude, time period) can easily and precisely be controlled by the experimental conditions such as the inflow rates and feed concentrations. The demonstrated phenomena can be exploited in practical applications, we use the non-autonomous pH oscillators to drive the reversible assembly and disassembly of pH-sensitive building blocks (oleic acid and gold nanoparticles), both highly relevant in nanotechnology and biomedical applications.