Reaction Kinetics Research Articles

Electrical monitoring of single-event protonation dynamics at the solid-liquid interface and its regulation by external mechanical forces

Detecting chemical reaction dynamics at solid-liquid interfaces is important for understanding heterogeneous reactions. However, there is a lack of exploration of interface reaction dynamics from the single-molecule perspective, which can reveal the intrinsic reaction mechanism underlying ensemble experiments. Here, single-event protonation reaction dynamics at a solid-liquid interface are studied in-situ using single-molecule junctions. Molecules with amino terminal groups are used to construct single-molecule junctions. An interfacial cationic state present after protonation is discovered. Real-time electrical measurements are used to monitor the reversible reaction between protonated and deprotonated states, thereby revealing the interfacial reaction mechanism through dynamic analysis. The protonation reaction rate constant has a linear positive correlation with proton concentration, whereas the deprotonation reaction rate constant has a linear negative correlation. In addition, external mechanical forces can effectively regulate the protonation reaction process. This work provides a single-molecule perspective for exploring interface science, which will contribute to the development of heterogeneous catalysis and electrochemistry.

Nitrogen and Sulfur Doped Porous Carbon Sheet with Trace Amount of Iron as Efficient Polysulfide Conversion Catalyst for High Loading Lithium-Sulfur Batteries.

The major challenges in enhancing the cycle life of lithium-sulfur (Li-S) batteries are the polysulfide (PS) shuttling and sluggish reaction kinetics (S to Li2S, Li2S to S). To alleviate the above issues use of hetero atom doped carbon as cathode host matrix is a low-cost and efficient approach as it works as a dual-functional framework for PS anchoring as well as electrocatalyst for faster redox kinetics. Here, the dual role of the Fe-containing heteroatom-doped carbon sheets (CS) in chemisorption of Li2S6 and catalyzing its faster conversion to Li2S is established through UV-Vis, XPS and CV studies. To substantiate the catalytic effect composite cathodes were prepared by encapsulating sulfur in CS which is further blended with carbon nanotubes (CNTs) to form free-standing cathode. The electrochemical performance of the three cathodes viz., S@Fe-N-CS-CNT, S@Fe-S-CS-CNT and S@Fe-NS-CS-CNT were evaluated by constructing Li-S cells. Among all, the S@Fe-NS-CS-CNT delivers a high initial discharge capacity of 1017 mAh g-1 at 0.5 C rate and sustains 751 mAh g-1 capacity after 260 cycles with a capacity retention of 73.8 %. Even at high S-loading (12 mg cm-2), it delivers an initial discharge capacity of 892 mAh g-1 and it retained 575 mAh g-1 after 200 cycles.

Visualization of the Distance-Dependent Synergistic Interaction in Heterogeneous Dual-Site Catalysis.

Understanding the characteristics of interfacial hydroxyl (OH) at the solid/liquid electrochemical interface is crucial for deciphering synergistic catalysis. However, it remains challenging to elucidate the influences of spatial distance between interfacial OH and neighboring reactants on reaction kinetics at the atomic level. Herein, we visualize the distance-dependent synergistic interaction in heterogeneous dual-site catalysis by using ex-situ infrared nanospectroscopy and in situ infrared spectroscopy techniques. These spectroscopic techniques achieve direct identification of the spatial distribution of synergistic species and reveal that OH facilitates the reactant deprotonation process depending on site distances in dual-site catalysts. Via modulating Ir-Co pair distances, we find that the dynamic equilibrium between generation and consumption of OH accounts for high-efficiency synergism at the optimized distance of 7.9 Å. At farther or shorter distances, spatial inaccessibility and resistance of OH with intermediates lead to OH accumulation, thereby diminishing the synergistic effect. Hence, a volcano-shaped curve has been established between the spatial distance and mass activity using formic acid oxidation as the probe reaction. This notion could also be extended to oxophilic metals, like Ir-Ru pairs, where volcano curves and dynamic equilibrium further evidence the universal significance of spatial distances.

Considerations for the safe handling and processing of unstable materials

AbstractWe evaluate the instability hazards of initiators, monomers, and other unstable materials during storage and handling in individual containers, pallets of containers, and storage and process vessels. We propose a simplistic model to analyze the temperature–time profile of an unstable chemical, given heat transfer from/to the environment, heat generation due to decomposition and other reaction kinetics, and heat generated from auxiliary equipment (e.g., agitators/mixers, pumps, vessel jackets). Lumped capacitance‐based heat transfer and decomposition kinetics are integrated to predict self‐accelerating decomposition temperature (SADT), self‐accelerating polymerization temperature (SAPT), and the temperature profile given exposure conditions (e.g., ambient temperature and additional sources of heat). Case studies related to the storage and processing of unstable liquid monomers (i.e., methyl methacrylate, MMA), and organic peroxides, (i.e., tert‐butyl peroxybenzoate, TBPB), are presented. We also provide recommendations on determining safe storage and processing temperatures and steps to prevent emergency situations and include an overview of thermal analysis and data treatment procedures which might affect chemical process safety recommendations.

Trance Amount of Ir Decorated NiFe Phosphide In-Situ Grown on Carbon Cloth as Cost-Effective Electrocatalyst for Oxygen Evolution Reaction.

Cost-effective electrocatalysts is a key constituent to establish the balance of cost and catalytic efficiency for oxygen evolution reaction (OER) via water electrolysis in the area of energy conversion and storage. NiFe phosphide decorated with trace amount of iridium (Ir) species in-situ grown on carbon cloth was prepared by a facile wet chemistry approach followed by a phosphorization post-treatment at a relative low temperature. The optimal electrocatalyst, Ir2-NiFePx/CC, exhibits excellent OER activity, with an low overpotential of 190 mV at 10 mA cm-2 for alkaline OER, and a desirable long-term durability over 90 h. The outstanding OER performance stems from the structural evolution via phosphorization process, Ir decoration with more high-valence stated Ir4+ species, and tight connection between individual components of the electrode, which gives rise to the strong activity to the active sites and faster reaction kinetics in the alkaline OER process. Mover, the Ir loading was as low as approximately ~1.7 wt% (0.29 mg cm-2), showing promissing propective in cost-effective OER.

IPLOT‐VKA: an Integral‐method Powell‐pLOT‐enhanced Visual Kinetic Analysis for the Determination of Orders of Reaction

Determination of partial orders of reactions in kinetics is a general entry step for any mechanistic investigation; recently, considerable attention has been given to the benefits of using visual methods to help in this task, such as easy utilization and data‐efficiency. In this respect, we here revisit and improve the classic method by Powell and Margerison for kinetic analysis. For the first time, analytical equations for a bimolecular reaction have been worked out for all values of partial orders of reactions, and the solutions have been implemented in a free, open‐access and easy‐to‐use Web‐application, named IPLOT‐VKA, which also allows estimation of the errors on the kinetic constant, and residual standard error on concentrations. Several examples, taken from reference teaching experiences and from recent literature in catalysis show the efficacy and accuracy of our approach, which also has the advantage of requiring less experimental runs than other visual methods currently available.

Reactivity Profiling for High-Yielding Ynamine-Tagged Oligonucleotide Click Chemistry Bioconjugations.

The Cu-catalyzed azide-alkyne cycloaddition (CuAAC) reaction is a key ligation tool used to prepare bioconjugates. Despite the widespread utility of CuAAC to produce discrete 1,4-triazole products, the requirement of a Cu catalyst can result in oxidative damage to these products. Ynamines are superior reactive groups in CuAAC reactions and require lower Cu loadings to produce 1,4-triazole products. This study discloses a strategy to identify optimal reaction conditions for the formation of oligodeoxyribonucleotide (ODN) bioconjugates. First, the surveying of reaction conditions identified that the ratio of Cu to the choice of reductant (i.e., either sodium ascorbate or glutathione) influences the reaction kinetics and the rate of degradation of bioconjugate products. Second, optimized conditions were used to prepare a variety of ODN-tagged products and ODN-protein conjugates and compared to conventional CuAAC and Cu-free azide-alkyne (3 + 2)cycloadditions (SPAAC), with ynamine-based examples being faster in all cases. The reaction optimization platform established in this study provides the basis for its wider utility to prepare CuAAC-based bioconjugates with lower Cu loadings while maintaining fast reaction kinetics.

Enhancing the Reaction Kinetics and Stability of Co-Free Li-Rich Cathode Materials via a Multifunctional Strategy.

Co-free Li-rich layered oxides (CFLLOs) with anionic redox activity are among the most promising cathode materials for high-energy-density and low-cost lithium-ion batteries (LIBs). However, irreversible oxygen release often causes severe structural deterioration, electrolyte decomposition, and the formation of unstable cathode-electrolyte interface (CEI) film with high impedance. Additionally, the elimination of cobalt elements further deteriorates the reaction kinetics, leading to reduced capacity and poor rate performance. Here, a multifunctional strategy is proposed, incorporating Li2MnO3 phase content regulation, micro-nano structure design, and heteroatom substitution. The increased content of Li2MnO3 phase enhances the capacity through oxygen redox. The smaller nanoscale primary particles induce greater tensile strain and introduce more grain boundaries, thereby improving the reaction kinetics and reactivity, while the larger micron-sized secondary particles help to reduce interfacial side reactions. Furthermore, Na⁺ doping modulates the local coordination environment of oxygen, stabilizing both the anion framework and the crystal structure. As a result, the designed cathode exhibits enhanced rate performance, delivering a capacity of 158 mAh g⁻¹ at 5.0 C and improved cyclic stability, with a high capacity retention of 99% after 400 cycles at 1.0 C. This multifunctional strategy holds great promise for advancing the practical application of CFLLOs in next-generation LIBs.

Hierarchical Equations of Motion for Quantum Chemical Dynamics: Recent Methodology Developments and Applications.

ConspectusQuantum effects are critical to understanding many chemical dynamical processes in condensed phases, where interactions between molecules and their environment are usually strong and non-Markovian. In this Account, we review recent progress from our group in development and application of the hierarchical equations of motion (HEOM) method, highlighting its ability to address some challenging problems in quantum chemical dynamics.In the HEOM method, the bath degrees of freedom are represented using effective modes from exponential decomposition of the bath correlation function. Complex spectral densities and low temperature simulations often require a larger number of modes, making the simulations very expensive. Recent advances, such as the barycentric spectral decomposition (BSD) technique, can significantly reduce the number of effective modes, allowing to handle complex spectral densities and enabling simulations at very low temperatures, including near-zero temperature dynamics.Another key improvement in the computational efficiency is the use of tensor network methods like matrix product states and hierarchical tensor networks. These techniques allow for efficient HEOM propagation with thousands of effective modes, crucial for simulating large molecular systems interacting with multiple baths. This combination enables simulations of excitation energy transfer (EET) in systems like the Fenna-Matthews-Olson (FMO) complex and even larger systems with experimentally determined spectral densities.The versatility of the HEOM method is demonstrated through applications to a wide range of chemical dynamics problems. Simulations of EET and related ultrafast spectroscopy are first briefly covered. Applications of the HEOM to quantum tunneling effects in proton transfer reactions are then presented. Early works have studied the non-Kramers dependence of the rate constant as a function of bath friction due to deep tunneling and revealed vibrationally nonadiabatic dynamics within the so-called nontraditional view of proton transfer reactions. A recent work on the large kinetic isotope effects in soybean lipoxygenase also indicated that many quantum correction approximations to classical transition-state theory may fall short in describing deep tunneling effects.Charge transport and separation dynamics in organic semiconductors are another area where the HEOM method has been instrumental. We first demonstrate that the HEOM provides a unified description of both band-like and thermally assisted charge carrier transport in organic materials. The effect of non-nearest neighbor transitions is then investigated by combining generalized master equations with exact memory kernels. The HEOM method also enables simulation of charge separation in organic photovoltaics (OPVs) and reveals how factors such as external electric fields, entropy, and charge delocalization influence the charge separation barrier and dynamics.Moreover, HEOM has been applied to investigate hydrogen atom scattering on the Au(111) surface and vibrational energy relaxation at molecule-metal interfaces. These studies provide deeper insights into how electron-hole pair excitations and temporary charge transfer states influence the nuclear motion, offering a new framework for simulating nonadiabatic dynamics on metal surfaces.In summary, the HEOM method has developed into a robust tool for simulating quantum effects in condensed phases. Future developments in algorithm efficiency and computational power will likely expand its applicability to even more complex systems.

Dynamic evolution processes in electrocatalysis: structure evolution, characterization and regulation.

Reactions on electrocatalytic interfaces often involve multiple processes, including the diffusion, adsorption, and conversion of reaction species and the interaction between reactants and electrocatalysts. Generally, these processes are constantly changing rather than being in a steady state. Recently, dynamic evolution processes on electrocatalytic interfaces have attracted increasing attention owing to their significant roles in catalytic reaction kinetics. In this review, we aim to provide insights into the dynamic evolution processes in electrocatalysis to emphasize the importance of unsteady-state processes in electrocatalysis. Specifically, the dynamic structure evolution of electrocatalysts, methods for the characterization of the dynamic evolution and the strategies for the regulation of the dynamic evolution for improving electrocatalytic performance are summarized. Finally, the conclusion and outlook on the research on dynamic evolution processes in electrocatalysis are presented. It is hoped that this review will provide a deeper understanding of dynamic evolution in electrocatalysis, and studies of electrocatalytic reaction processes and kinetics on the unsteady-state microscopic spatial and temporal scales will be given more attention.

Design of PtSn Nanocatalysts for Fuel Cell Applications.

The challenges in the fuel cell industry lie in the cost, performance, and durability of the electrode components, especially the platinum-based catalysts. Alloying has been identified as an effective strategy to reduce the cost of the catalyst and increase its efficiency and durability. So far, most studies focused on the design of PtM bimetallic nanocatalyst, where M is a transition metal. The resulting PtM materials show higher catalytic activity, but their stability remained challenging. In addition, most of the transition metals M are expensive or low abundant. Tin (Sn) has gained attention as alloying element due to its versatility in manufacturing both anode and cathode electrodes. If used as anode catalyst, it is able to overcome poisoning from CO and related intermediates. As cathode catalyst, it improves the kinetics of the oxygen reduction reaction (ORR). Additionally, Sn is an abundant and cheap element. The current contribution outlines the state of the art on the alloy and shape effect on PtSn activity and stability, demonstrating its high potential to develop cheaper, more efficient and durable catalysts for fuel-cell electrodes. Additionally, in situ analytical and spectroscopic studies can shed light on the elementary steps involved in the use of PtSn catalytic systems. Finally, this intriguing material can be used as a parent system for the synthesis of high-entropy-alloys and intermetallics materials.

A Kinetic Model for Oxide–Carbonitride Inclusion Heterogeneous Nucleation and Precipitation during Superalloy Solidification

Complex oxide–carbonitrides (MgO-Ti(CN), Al2O3-Ti(CN), and MgO·Al2O3-Ti(CN)) are the most common non-metallic inclusions presented in cast and wrought superalloys. In this work, a coupled kinetics model was proposed to predict the complex oxide–carbonitride inclusion’s precipitation behavior during the solidification of superalloys. This model takes into account thermodynamics, micro-segregation, heterogeneous nucleation in the inter-dendritic liquid, and growth controlled by the diffusion of solute elements and kinetics of interfacial reaction. The results demonstrated that both the cooling rate and nitrogen content take significant effects on the final size of complex oxide–carbonitride inclusions, as the former controls the total growth time and the latter determines the initial precipitation temperature. In comparison, the particle size of primary oxides shows a negligible impact on the final size of complex inclusions. The practice of an industrial vacuum arc remelting confirmed that the inclusion size variation predicted by the present model is reasonably consistent with the experimental results.

Multiscale Defective Interfaces for Realizing Na-CO2 Batteries With Ultralong Lifespan.

Despite their favorable high energy density and potential for CO2 recycling, Na-CO2 batteries have been held back by limitations in cycling capability, stemming from the sluggish CO2 reduction/evolution reaction (CO2RR/CO2ER) kinetics at CO2 cathode and unmanageable deposition/stripping of metallic Na at the anode upon cycling. Herein, a "two-in-one" electrode with multiscale defective FeCu interfaces (CP@FeCu) is presented, which is capable of improving the CO2RR/CO2ER kinetics of CO2-breathing cathode, while modulating sodium deposition behavior. Experimental and theoretical investigations reveal multiscale defective FeCu interfaces are responsible for the enhancement of sodiophilicity and catalytic properties. The defect and valence oscillation effects originate in multiscale defective FeCu interfaces, effectively facilitating the adsorption of reactants and decomposition of Na2CO3 during CO2RR/CO2ER processes, along with exceptional cycling stability of 2400 cycles (4800h) at 5µAcm-2. Meanwhile, the CP@FeCu with sodium affinity creates a uniform electric field and robust adsorption for Na, making initial nucleation sites more conducive to Na deposition and achieving dendrite-resistant and durable anodes. This work offers a scientific insight into the functionalization design of "two-in-one" electrodes, which is essential for a unified solution to the challenges in sodium anodes and CO2 cathodes.

Engineering interfacial molecular interactions on Ag Hollow fibre gas diffusion electrodes for high efficiency in CO2 conversion to CO.

The electrochemical CO2 reduction reaction (CO2RR) occurs at the nanoscale interface of the electrode-electrolyte. Therefore, tailoring the interfacial properties in the interface microenvironment provides a powerful strategy to optimise the activity and selectivity of electrocatalysts towards the desired products. Here, the microenvironment at the electrode-electrolyte interface of the flow-through Ag-based hollow fibre gas diffusion electrode (Ag HFGDE) is modulated by introducing surfactant cetyltrimethylammonium bromide (CTAB) as the electrolyte additive. The porous hollow fibre configuration and gas penetration mode facilitate the CO2 mass transfer and the formation of the triple-phase interface. Through the ordered arrangement of hydrophobic long-alkyl chains, CTAB molecules at the electrode/electrolyte interface promoted CO2 penetration to active sites and repelled water to reduce the activity of competitive hydrogen evolution reaction (HER). By applying CTAB-containing catholyte, Ag HFGDE achieved a high CO Faradaic efficiency (FE) of over 95 % in a wide potential range and double the partial current density of CO. The enhancement of CO selectivity and suppression of hydrogen was attributed to the improvement of charge transfer and the CO2/H2O ratio enhancement. These findings highlight the importance of adjusting the local microenvironment to enhance the reaction kinetics and product selectivity in the electrochemical CO2 reduction reaction CO2RR.

Insights into the Deterioration Mechanism of Charging Ability during Calendar Aging and Cycling Aging of High-Voltage Co-Poor NCM Cathode-Graphite Full Battery.

Lithium-ion battery (LIB) has gained significant recognition for the power cell market owing to its impressive energy density and appealing cost benefit. Among various cathodes, a high-voltage cobalt-poor lithium nickel manganese cobalt oxide cathode (Co-poor NCM cathode) has been considered as a promising strategy to enhance its energy density. Despite these advantages, high-voltage Co-poor NCM cathode-graphite full battery usually suffers from poor rate performance. However, fast charging has been a key indicator for widespread application of power batteries. Although many efforts have been made to improve the charging performance of fresh batteries, few works investigate the charging ability during calendar aging and cycling aging of high-voltage Co-poor NCM cathode-graphite full battery. In this work, we found that the charging ability becomes worse during calendar aging and cycling aging. Results showed that the increasing charge transfer resistance from the cathode is the major obstacle to achieving fast charging during the aging process. To address the problem, high-voltage Al2O3-coated Co-poor NCM cathode successfully prepared via a simple atomic layer deposition (ALD) method has been developed to reduce the decay of charging performance during calendar aging and cycling aging. Al2O3-coated NCM cathode can effectively reduce the growth rate of the resistance of cathode, which is benefiting from the conversion of Al2O3 into LiAlO2 with high ionic conductivity and the restriction formation of rock salt phase. Benefiting from the decreased charge transfer resistance of the NCM cathode, the mismatch of the lithium-ion reaction kinetics is well alleviated, thus effectively reducing the polarization under fast charging. As a result, Al2O3-coated NCM cathode-graphite full battery shows the slow deterioration of charging performance during the aging process. This work provides a promising strategy for constructing fast-charging batteries during calendar aging and cycling aging.

An Oriented Diffusion Strategy to Configure All-Region Ultrahigh-Density Metal Single Atoms for High-Capacity Sodium Storage.

Single-atom metals (SAMs), despite being promising for high-utilization catalysis, biomedicine, and energy storage, usually suffer from limited catalytic performance caused by low metal loading. Herein, via an oriented diffusion strategy, all-region ultrahigh-loading (18.9wt.%) Sn-SAMs over carbon nanorings matrix (Sn-SAMs@CNR) are initially achieved based on the transformation of a g-C3N4@SnO2@polydopamine ring-like nested structure. The formation process of Sn-SAMs involves a critical conversion from oxygen-coordination (SnO2) to nitrogen-coordination (Sn-N4) and simultaneous anti-Osterwalder ripening promoted under spatial confinement. Notably, the g-C3N4-derived N-containing gaseous intermediates dynamically drive the oriented diffusion (inside-out diffusion) of Sn-SAMs across the carbon nanorings, realizing an all-region ultrahigh loading of SAMs throughout the carbon matrix. This strategy is also applied to other metal materials (Fe, Co, Ni, Cu, and Sb), and features excellent universality. When applied as the anode for sodium-ion batteries, experimental analyses and theoretical calculations demonstrate that high-loading Sn-N4 active sites significantly optimize electron density distribution and improve reaction kinetics. Consequently, Sn-SAMs@CNR exhibits outstanding durability of 364mAhg-1 even after 5000 cycles with an impressively low (0.00068%) capacity decay per cycle. This work opens up a universally new avenue for all-region ultrahigh loading of SAMs to carbon matrix for high-performance energy storage.

The Construction of Face-to-Face Combination between NiFe-layered Double Hydroxide Nanosheets and Monolayer rGO for Efficient Water Splitting and Oxygen Reduction.

Developing cost-effective and efficient electrocatalysts is essential for advancing a green energy future. Herein, a NiFe-layered double hydroxide loaded on reduced graphene oxide (NiFe-LDHs@rGO) hybrid was synthesized using a straightforward three-step process involving exfoliation tearing, electrostatic self-assembly, and chemical reduction. The face-to-face packing and ultrathin exfoliation enable strong heterogeneous interactions, fully harnessing the potential of these complementary two-dimensional counterparts. Consequently, the resultant catalyst displays outstanding oxygen evolution reaction (OER) catalytic activity and stability, whose overpotential is as low as 241 mV at 30 mA cm-2 and 255 mV at 50 mA cm-2 with a low Tafel slope of 62.1 mV dec-1. Both the experimental results and density functional theory (DFT) calculations reveal that the face-to-face assembly strengthens the electronic interactions between NiFe-LDHs and rGO, which effectively modulates the d-band center of Ni and Fesites and improves the reaction kinetics for OER. Moreover, the resultant NiFe-LDHs@rGO hybrids exhibit excellent multifunctional catalytic performance. Its hydrogen evolution reaction (HER) activity is endowed by Fe-site of NiFe-LDHs and defect states rGO and achieves a low voltage of 1.68 V to drive a current density of 10 mA cm-2 for overall water splitting. The face-to-face heteroassembly also imparts NiFe-LDHs@rGO with superior oxygen reduction reaction (ORR) activity, with a half-wave potential of 0.70 V and a limiting current density of 4.2 mA cm-2. Its ORR primarily follows a four-electron transfer pathway with a minor contribution from a two-electron process. This study establishes the groundwork for optimizing two-dimensional heterogeneous interfaces in LDH@carbon-based materials for advanced energy conversion.

Ethylamine as a regenerative fuel for emission-free direct liquid fuel cell

Discovery of energy-dense and emission-free fuels for low-temperature fuel cell technology remains an important research theme to achieve efficient, clean electricity generation. In this study, we report the study of ethylamine as a regenerative fuel for emission-free fuel cells. The electrocatalytic ethylamine dehydrogenation reaction on commercial Pt catalyst under alkaline conditions exhibits fast reaction kinetics and produces acetonitrile as sole product, which can be readily hydrogenated back to ethylamine for reuse and thereby avoid CO2 emissions. By assembling and testing a direct ethylamine fuel cell, we demonstrate the capability of this regenerative fuel for clean electricity generation. The fuel cell performances are evaluated with different ethylamine fuel concentrations and operation temperatures and compared with other direct liquid fuel cells, highlighting promising prospects for utilizing ethylamine as a regenerative fuel in fuel cells for efficient and clean electricity generation.

Differentiating Reactive Oxygen Species with DNA Framework Monitors.

The lifespan, oxidizing properties, bonding behaviors, and reactivity of reactive oxygen species (ROS) produced during photocatalytic activation can vary significantly due to the differences in electron configurations of ROS, which are dependent on their generation mechanisms: energy transfer or charge transfer. Hence, identifying and differentiating ROS of different mechanisms can improve our understanding of redox reactions and related diseases, providing a basis for the prevention and treatment of related diseases. Here, we have developed a DNA framework monitor (DFM) based on dynamic DNA structural changes to effectively distinguish the two types of ROS produced in photocatalytic activation of O2. This DFM provides a visualization tool for observing the reaction kinetics of ROS with DNA, not only distinguishing two types of ROS with different mechanisms but also serving as a universal system for evaluating the efficacy and performance of nanomaterials for ROS regulation.

Comparison of non-premixed and premixed flamelets for ultra WET aero engine combustion conditions

The Water-Enhanced Turbofan (WET) is a future concept for aero engine applications being developed by MTU Aero Engines AG. Steam is injected into the combustion chamber to reduce temperature peaks and emission of pollutants. Depending on the steam content, the combustion process is modified. To analyze the effect of steam on the reaction kinetics and the temperature, detailed chemistry has to be employed. By comparing laminar flame speed and mole fraction distribution across the flame front, an appropriate chemical mechanism for the considered operating conditions including high steam loads was selected. Tabulated chemistry based on flamelets was employed, which enables the use of complex mechanisms in CFD analysis at reasonable computational costs. A comparison of premixed freely propagating flames and non-premixed counterflow diffusion flames to represent the manifolds was investigated. Various definitions of the progress variable are studied for ultra WET combustion considered under aero engine conditions. The manifolds from both model flames are compared from dry to ultra WET conditions with kerosene in an adapted Sandia Flame D large eddy simulation. While the premixed flamelets are generated efficiently, the results obtained with non-premixed flamelets are more reliable for the range of operating conditions investigated.