Intrinsic Kinetics Research Articles

Intrinsic combustion kinetics of rapid-pyrolysis Zhundong coal char

Driven by the demand for accurate intrinsic kinetics for the prediction of the combustion rate of purely fired Zhundong coal (ZDC) in a slag tapping boiler, the surface activation function (SAF) and intrinsic kinetic parameters of two types of rapid-pyrolysis ZDC chars were revealed via the isothermal and nonisothermal thermogravimetric analysis methods. The isothermal kinetic results show that the activation energy (E), reaction order and SAF of these two chars were the same, at 146 kJ/mol, 0.78 and X0.44 (1 – X)−0.48, respectively. Therefore, the difference in the intrinsic reaction rate between these two chars was caused only by the different pre-exponential factors, which are mainly influenced by the specific surface area and catalytic elements in char ash. Nonisothermal kinetic parameters were obtained via the isothermal model-fitting method (ISOM), thereby using the isothermal SAF to fit the nonisothermal data at different heating rates (βs). The results indicate that the E values of the two chars were 148.95 ± 3.12 kJ/mol and 146.16 ± 1.66 kJ/mol, indicating that β has little influence on E. These measured values are consistent with the isothermal E values, so the ISOM is suitable for the determination of the nonisothermal kinetics of rapid-pyrolysis char combustion.

Rotating Disk Electrode Standardization and Best Practices in Acidic Oxygen Evolution for Low-Temperature Electrolysis

Efforts in oxygen evolution catalyst development have significantly increased and often use rotating disk electrode half-cells to evaluate intrinsic kinetics and screen materials for short-term durability. Standardizing rotating disk electrode test protocols is critical to experimental accuracy, to realistically assess their potential impact at a device level and to assess how different catalyst approaches and concepts are prioritized. The goal of this study is to provide standardized test protocols and suggest best practices to help reduce variability in ex situ materials characterization in the broader community. Specifically, these protocols focus on test cleanliness and materials choices, including how electrodes are prepared and tested, and the impact on activity observations.

Fast charge separation and transfer strategy in polymeric carbon nitride for efficient photocatalytic H2 evolution: Coupling surface Schottky junctions and interlayer charge transfer channels

Reinforcing the charge separation and transfer in layered polymeric carbon nitride (PCN) is the key issue to enhance its photocatalytic activity but still remains very challenging. Herein, for the first time, the synergetic Pd single atoms (PdSAs) and carbon-supported Pd nanoparticles (NPs) are introduced into the interlayer and surface of layered PCN respectively to address this challenge. The PdSAs are in intimate contact with the adjacent PCN layers and serve as interlayer charge transfer channels, while the carbon-supported Pd NPs contribute to multistep PCN-carbon-Pd NPs Schottky junctions on PCN surface. Experiments and theoretical calculations demonstrate that such unique architectures provide intrinsic driving force to extract the electrons from PCN to outermost Pd NPs with high migration rate via vertical PdSAs channels. This directional charge transfer in PCN greatly expedite the separation of charge carriers in both inner and surface of PCN and simultaneously yield electron-rich Pd NPs active sites with optimized H2 adsorption energy, thus leading to improved intrinsic H2 evolution reaction kinetics. Consequently, the Pd/PCN2 performs ultrahigh photocatalytic H2 evolution rate of 83.34 mmol g−1 h−1 in the dispersed particulate system and 100.4 mmol h−1 m−2 in the film form under simulated sunlight. This work provides a new promising approach to engineer the spatial charge transfer behaviors for high-performance PCN-based photocatalysts.

Oxygen Vacancies‐Rich TiO2/C Nanofibers with Boron, Nitrogen Dual‐Doping for Ultrafast Sodium Storage

AbstractTiO2 is an intercalation pseudocapacitive material with low potential and minor structural changes during the sodium storage process. However, the intrinsic electronic conductivity and ionic diffusion kinetics are not unsatisfactory for ultrafast sodium storage. Defect engineering plays a pivotal part in improving the sodium storage kinetics of TiO2 anode materials. Now the common defect regulation methods are complicated. Herein, a simple NaBH4 reduction method is proposed to produce rich oxygen vacancies and boron doping in nitrogen‐doped TiO2/C mesoporous nanofibers, and the finally obtained oxygen vacancies (OVs)‐rich TiO2/C nanofibers (TC‐OVs) also build internal vertical channels. This particular structure of TC‐OVs favors fast transport for electrons and ions, resulting in ultrafast rate capability (156 mAh g−1, 2 A g−1) and long lifespan (139 mAh g−1, 1000 cycles, 1.0 A g−1). The inspiring sodium storage performance of TC‐OVs benefits from the high pseudocapacitance contribution (94%, 5.0 mV s−1). This work provides a method to adjust defects and structures of TiO2 electrode materials for ultrafast chemical energy storage.

Efficient removal of antimony by a facile liquid-controlled strategy reinforced hematite-spinel (Fe2O3-MnFe2O4) composite: construction, simulation and practical evaluation

Currently, aqueous antimony contamination has become a non-negligible issue due to its scale industrious production and potential health risk. Herein, we prepare a novel hematite-spinel (Fe2O3-MnFe2O4) adsorbent by a one-step hydrothermal method for aqueous antimony deep purification, in which interfacial Fe-Mn bidentate complex sites are determined as the reinforced one by X-ray absorption spectroscopy (XAS) analysis and density functional theory (DFT) simulation. Through facile alkaline control by NH3·H2O and Fe/Mn proportion adjustment, the intrinsic synthesis kinetics of materials are precisely regulated that MnFe2O4 nano-particles successfully in-situ form on the Fe2O3 surface, in which sufficient adsorption sites are guaranteed by the small size effect. The adsorption experiment further demonstrates that the composite material is effective in Sb(III) and Sb(V) elimination, in which the adsorption capacity reaches up to 42.7 (Sb(III)) and 32.4 mg·g−1 (Sb(V)) (initial concentration 5.0 mg·L−1). The Sb K edge Extended X-ray absorption fine structure (EXAFS) analysis shows that antimony molecules occur as two typical complexation forms on the MnFe2O4 interface, in which an edge-sharing with Fe-O octahedron (Fe-Fe-ES) and two corner-sharing with Fe-O octahedron and Mn-O tetrahedron (Fe-Mn-CS) are exhibited. Further DFT calculations indicate that the Fe-Mn-CS has the highest adsorption energy for Sb(III) (-3.31 eV) and Sb(V) (-5.12 eV), which is rationally interpreted by the compatible overlapping of Fe 3d and O 2p as well as interfacial electron redistribution in Mn atom. This work may represent a new strategy in structure design and provide an alternative perspective in adsorption mechanism illustration.

Treating NOx emission of hydrogen fueled combustion engines by NOx storage and reduction catalysts: A transient kinetic study including PLIF measurements

NOx storage and reduction (NSR) catalysts are a well-known and broadly used technology to reduce NOx emissions from combustion engines, which may also be applied for hydrogen fueled engines in the future. In this study, Pt- and Pd-based NSR-catalysts were investigated in the absence and presence of water to understand how NO oxidation as well as the storage and reduction phases are influenced by the gaseous environment with H2 as a reductant. A planar channel configuration was chosen for conducting planar laser-induced fluorescence experiments during the storage phase in addition to steady-state oxidation measurements and transient lean/rich cycles in a packed bed reactor. The presence of steam significantly decreases the NO oxidation activity of both noble metal catalysts. The Pt/BaO/Al2O3 catalyst is more active during transient lean/rich cycles, however, it suffers an activity loss during repeated cycles, whereas the activity of the Pd/BaO/Al2O3 sample is slightly more stable in the wet gas feed over time. All experiments showed a strong correlation between the NO2 formation over the catalyst and its storage capability. The influence of water in the exhaust gas on the NSR-catalysts shows a strong temperature dependency on storage and reduction of NO for both catalysts containing Pt and Pd. The storage behavior is also strongly influenced by both the experimental configurations chosen revealing the significance of the interaction of intrinsic catalytic kinetics and mass transfer in the surrounding flow field.

Kinetic Study of the Water‐Gas Shift Reaction at Ultralow Temperature over a Ru‐Based Supported Ionic Liquid Phase Catalyst

AbstractThe water‐gas shift reaction is subject to thermodynamic limitation, i.e., CO conversion increases with decreasing temperature. Thus, it is preferential to keep temperatures as low as possible at reasonable kinetic rates. In this work, the performance of a ruthenium‐based supported ionic liquid phase catalyst is shown for the water‐gas shift reaction at ultralow temperature. Furthermore, a model for the intrinsic kinetics of the water‐gas shift reaction using this supported ionic liquid phase catalyst is presented. For this purpose, a formal kinetic power law and a mechanistic general catalytic cycle kinetic approach were applied. Supported ionic liquid phase catalysts with filling levels up to 30 % were prepared. For filling levels < 13 %, internal mass transport limitations do not occur and intrinsic kinetics prevail.

Simulation and experimental study on mechanism and kinetics of 1,1,2-trichloroethane dehydrochlorination reaction

Dehydrochlorination of 1,1,2-trichloroethane (112TCE) is a widely used method for preparing vinylidene chloride (VDC), which is an important polymeric monomer and intermediate of refrigerant. However, there are few reports on kinetics of this reaction system. In this work, density functional theory (DFT) calculation analyses and experiments were conducted to investigate the reaction mechanism and kinetics of 112TCE dehydrochlorination with sodium hydroxide (NaOH). DFT simulation results unveiled there were three parallel reactions which produce VDC, cis-1,2-dichloroethylene (C12DE) and trans-1,2-dichloroethylene (T12DE) respectively in the reaction process of 112TCE and NaOH. The activation energy of the reaction to produce VDC was lower than those of the other two reactions. Moreover, the kinetic parameters of the three parallel reactions, such as reaction orders, rate constants, pre-exponential factors and activation energies, were experimentally obtained by decoupling the overall reaction kinetics. All the parallel reactions are bimolecular elimination reactions and the rate expression of the intrinsic kinetics for generating VDC isdCtdt=1.668×1011e-75662RTCACB. The reaction rate is three orders of magnitude higher than those of producing C12DE and T12DE, which is consistent with the DFT simulation results. These kinetics results are useful for the process optimization and reactor design in VDC production process.

Bulk oxygen conduction kinetics of iron oxides on the chemical looping combustion

Oxygen-ion conduction is generally considered the rate-determining step during the chemical looping combustion process, which is vital for the design of the oxygen carriers. However, the redox reaction is heavily influenced by gas diffusion, making it very difficult to derive convincing intrinsic kinetic data. This work aims to establish a methodology to evaluate the intrinsic kinetics of oxygen carriers for chemical looping combustion by using an ultra-thin oxygen conducting membrane to exclude the influence of gas diffusion. From mass balance and Fick's second law, a mathematical kinetics model describing the intrinsic oxygen conduction performance was established. The intrinsic activation energy took value of 77.84 kJ/mol for pure Fe2O3. The kinetics parameters can be used for the high throughput design and screening of oxygen carriers.

Challenges and recent progress in unraveling the intrinsic pH effect in electrocatalysis

The kinetics of many electrode reactions, especially those involving the consumption/production of H + /OH − , show significant pH dependence. Systematic studies of the pH effect over a wide pH range can provide very useful information about their reaction mechanism(s) and help figure out the optimum reaction conditions. For fast electrode reactions in solutions of medium pH and low buffer capacity, correcting the effects induced from the shift of local pH near the electrode−electrolyte interface (pH s ) is a prerequisite for unraveling the intrinsic kinetics and its pH dependence. In this review, recent progress on how to estimate the pH s , how to eliminate the effect induced by pH s shift and how to deduce the pH dependent intrinsic reaction kinetics are summarized. Mechanistic and kinetic implication of pH effect on electrocatalytic processes will be discussed by taking formic acid/formate oxidation at Pt electrode as an example.

Electrochemical characterisation of macroporous electrodes: Recent advances and hidden pitfalls

Investigating the intrinsic kinetics of macroporous electrodes by means of cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) is an exceptionally challenging task with a multitude of hidden pitfalls. The classical analysis (e.g. the Randles–Ševčík or the Nicholson methods) cannot be used for macroporous electrodes as these can only be applied to electrodes which exhibit mass transport controlled by planar semi-infinite diffusion and that have spatially uniform redox activity. Unfortunately, a number of recent articles incorrectly interprete data by applying classical analysis to macroporous electrodes. To address this, the CV and EIS analysis methods, which can be used for macroporous electrodes are reviewed and discussed.

Multiple‐Scale Probing of Intrinsic Active Sites and Reaction Kinetics in Processable Cation‐Inserted Nickel Hydroxide Films

AbstractNanoplate‐shaped Ni(OH)2 with numerous exposed active sites hold much promise for high‐performance energy storage devices. However, restricted by the wide band gap, which leads to a low concentration of charge carrier, the energy barrier of electron mobility in lattice plane is high, further inhibiting the electron transfer and their practical application. Here, several unique processable nickel‐based hydroxide films are constructed via the cation‐inserted strategy to probe the intrinsic relationship between component and electronic micro‐structure. Benefiting from the component‐driven effects, the concentration of charge carrier at the lattice plane can be accumulated after injecting heterogeneous cations, and the fastened dynamics process can be realized and confirmed by multiple real‐time operando techniques. Meanwhile, the more well‐matched Co core rather than Mn core in Ni(OH)2 is also certified. Finally, the CoNi(OH)2 electrode achieves 623 C g–1 @1 A g–1 without any conductivity additives and binders, which is nearly threefold that of pristine Ni(OH)2. This work clarifies the critical role of inserted cations, and corresponding electron and electrolyte ion transfer across the matrix, thus enabling a better guideline for Ni(OH)2‐based energy storage/conversion systems.

Kinetic modelling and experimental validation of single large particle combustion of coal char

Understanding apparent kinetics of single large fuel particle combustion is of significance to the design and optimization of grate-firing and circulating fluidized bed boilers. Based on the concept of finite reaction zone approximation, a simple heterogeneous single particle model was formulated to consider the effects of external gas film, ash layer and chemical reaction simultaneously. To validate the proposed model and gain insight into the prevailing rate-controlling mechanism during the single particle combustion process at different combustion temperatures and particle sizes, the experiments on the combustion of coal char powder and single large char particles were carried out in a thermal gravimetric analyzer and a bench scale fixed-bed reactor, respectively. The intrinsic and apparent kinetics as well as the effective reacting zone thickness of single large particle combustion were quantified by combining theoretical analyses and experimental data. Both the bulk flow temperature and particle size have a remarkable influence on the global reactivity. The rate-controlling process was found to shift from the intrinsic chemical reaction to ash layer diffusion and return again to the intrinsic kinetics at the burnout stage. Particularly, an external effectiveness factor was defined as a function of conversion degree to better describe the ash diffusion effect on the apparent reactivity of large particles. The proposed model is physically general but simple enough to be incorporated into the computational fluid dynamic simulation of large-scale grate-firing and fluidized bed boilers.

Luminescence properties and time-resolved spectroscopy of rare-earth doped SrMoO4 single crystals

Luminescence properties of nominally pure and doped with Eu3+ and Pr3+ ions SrMoO4 single crystals grown by the Czochralski method have been studied. Thermal quenching of intrinsic emission of pure and doped SrMoO4 single crystals has been observed, as well as a correlation of thermal quenching activation energies with rare-earth ion concentration has been observed. Tunable laser was used to study time-resolved luminescence in a range from 10 K to room temperature. The effect of dopant nature and concentration on intrinsic emission and decay kinetics has been elucidated.

Extrusion 3D printing of keratin protein hydrogels free of exogenous chemical agents

Keratins are a class of intermediate filament proteins that can be obtained from numerous sources including human hair. Materials fabricated from keratins offer desirable characteristics as scaffolds for tissue engineering, including intrinsic cell adhesion sequences and tunable degradation kinetics. The capacity to create 3D printed constructs from keratin-based bio-inks generates unique opportunities for spatial control of scaffold physicochemical properties to direct scaffold functions in ways not readily achieved through other means. The aim of this study was to leverage the controllable rheological properties of keratin hydrogels to create a strategy for extrusion 3D printing of keratin bio-inks without the use of exogenous rheological modifiers, crosslinking agents, or photocurable resins. The rheological properties of keratin hydrogels were tuned by varying two parameters: (a) the ratio of keratose (obtained by oxidative extraction of keratin) to kerateine (obtained by reductive extraction of keratin); and (b) the weight percentage of total keratin protein in the gel. A computational model of the dispensing nozzle for a commercially available extrusion 3D printer was developed to calculate the needed pneumatic printing pressures based on the known rheological properties of the gels. Keratin hydrogel constructs, of varying keratose/kerateine ratios and total keratin weight percentages, were 3D printed in cylindrical geometries via extrusion 3D printing. Rheology and degradation studies showed that gels with greater relative kerateine content exhibited greater flow resistance and slower degradation kinetics when submerged in phosphate buffered saline solution at 37 °C, owing to the presence of cysteine residues in kerateine and the capability of forming disulfide bonds. Total keratin weight percentage was found to influence gel yield stress, with possible implications for tuning filament fidelity. Findings from this work support the use of keratose/kerateine ratio and total keratin weight percentage as handles for modulating rheological characteristics of keratin hydrogels to enhance printability and control scaffold properties.

A porous V/SiO2 sphere composite for the selective oxidation of benzyl alcohol to benzaldehyde in aqueous phase through peroxymonosulfate activation

A porous V/SiO2 sphere composite (VOX@SiO2) was synthesized using one-step sol-gel method. Benefiting from the redox properties of vanadium and the hydrophilic property, VOX@SiO2 showed good catalytic performances for the selective oxidation of benzyl alcohol (BzOH) to benzaldehyde (BzH) in aqueous phase through peroxymonosulfate (PMS) activation, and performed far better in water than in various organic solvents. The redox cycle of VV/VIV was supposed to be responsible for PMS decomposition in the VOX@SiO2/PMS system. The SO4∙-, 1O2 and mediated electron transfer were revealed to play a major role in the selective oxidation of BzOH to BzH. The intrinsic kinetics was analyzed to calculate the chemical reaction rate (ra) and reaction order (n = 0.33) with respect to BzOH. This study provided some insights into the development of vanadium-based heterogeneous catalyst for the selective oxidation of BzOH to BzH through PMS activation.

Design of multistage fixed bed reactors for SMR hydrogen production based on the intrinsic kinetics of Ru-based catalysts

In recent years, interest in the development of a hydrogen economy has increased, and the steam methane reforming (SMR) reaction, which yields so-called “gray” hydrogen, is expected to play a key role in hydrogen refueling stations (HRSs) in the interim before “green” hydrogen process is developed. For this purpose, compact and economical designs for small- to medium-scale SMR processes for HRSs are required. Herein, we investigated the intrinsic kinetics of a Ru-based catalyst using catalyst experiments and parametric estimation. In addition, reactor modelling was performed using a kinetic model with a special focus on multistage reactor configurations. The proposed reactor design showed an increase in the reactor energy supplied rate from 6.98 to 7.55 kW compared to the base case (single-stage reactor), and the conversion increased from 86.2% to 91.2%. Further, the drastic temperature drop owing to the strongly endothermic nature of the SMR reaction was reduced, and, thus, reactor stability was improved. The proposed novel design of a multistage reactor using a Ru-based catalyst will advance the development of the hydrogen economy.

Clean Process to Utilize the Potassium-Containing Phosphorous Rock with Simultaneous HCl and KCl Production via the Steam-Mediated Reactions.

In this paper, a clean process based on the steam-mediated reactions for simultaneous HCl and KCl production using the potassium (K)-containing phosphorous rock as a precursor is proposed. Through hydrochloric acid (HCl) leaching, not only the generation of H3PO4 and CaCl2 (via further precipitation) were realized but also the acid-insoluble residue [phosphorous-rock slag (PS)] rich in elements, that is, K, Al, Si, and so on, in the form of microcline (KAlSi3O8) and quartz (SiO2) was obtained and became readily available for further HCl and KCl generation. Over 95% of the elements, that is, K, Al, and Si, come into the final products, and the overall acid consumption (based on HCl) is significantly reduced (90%) due to recovery of acids. The impacts of the key operational parameters such as temperature, duration, and reagent impregnate ratio were rigorously analyzed via a supervised machine learning approach, and the optimal conditions were determined [reaction temperature, X1, 850 °C; reaction duration, X2, 40 min; and impregnate ratio (PS over CaCl2), X3, 2.5] with approximately ±10% uncertainties. Thermodynamic analysis indicates that the introduction of steam to PS + CaCl2 not only enhances the chemical potential for the formation of HCl and KCl but also provides the transport advantage in continuously removing the generated products, that is, HCl and KCl, out of the system. Molecular simulation indicates that the presence of both steam and SiO2 in the PS matrix plays critical roles in decomposing PS + CaCl2 at high temperature. The shrinking core model shows that both the intrinsic kinetics and transport are influential with the activation energy being around 14.63 kJ/mol. The potential reaction pathway is postulated.

(Energy Technology Division Research Award) Interplay between Synthesis, Mechanisms and Performance of Electrocatalysts and Ionomers for Ion-Exchange Membrane Fuel Cells

Ion-exchange membrane fuel cells (IEMFCs) are a family of electrochemical energy conversion and storage devices characterized by several attractive features, including outstanding energy conversion efficiency and a clean operation. IEMFCs are a cornerstone of the “hydrogen economy”, one of the most promising avenues to decarbonize the energy sector, with the ultimate purpose to curtail the emissions of greenhouse gases and mitigate global warming. Therefore, a goal of great practical relevance is to devise highly performing, durable and inexpensive IEMFCs .IEMFCs consist of an electrolyte membrane sandwiched between two electrodes. At the membrane-electrode interfaces are located electrocatalytic layers (EC layers) comprising suitable electrocatalysts (ECs) able to promote the redox processes exploited by the IEMFC operation. The IEMFC sub-families are distinguished by the attributes of the membrane, especially in terms of: (i) chemical features (e.g., polymeric backbone); (ii) mobile ion(s) (e.g., protons for proton-exchange membrane fuel cells, PEMFCs, OH- anions for anion-exchange membrane fuel cells, AEMFCs); and (iii) operation temperature. In the environment modulated by the ionomer, the properties of the ECs , with particular reference to the chemical composition of the active sites and support morphology, are correlated to their performance. Hence, to obtain an IEMFC exhibiting a high performance and durability is imperative to rationally design membranes and ECs that are: (i) highly compatible with one another; and (ii) able to express their best performance and durability in the same set of operating conditions.This contribution overviews our research activities aimed at the development of ECs and membranes for application in PEMFCs, high-temperature PEMFCs and AEMFCs. The topics include: (i) the innovative approaches for the synthesis of the functional components; (ii) the aspects of their physicochemical characterization, together with the unique and comprehensive frameworks contrived for the integration and interpretation of the experimental outcomes; and (iii) the steps to integrate the functional components in high-performing IEMFC prototypes.The ECs considered here are meant to promote the oxygen reduction reaction (ORR), a sluggish electrochemical process that is a major bottleneck in the operation of IEMFCs fueled with hydrogen. State-of-the-art ORR ECs are based on Pt nanoparticles supported on carbon (“Pt/C” ECs). Pt/C ECs warrant a sufficient performance, but suffer from a poor durability and require a high loading of platinum, a strategic element that is prone to trigger supply bottlenecks especially in the event of a large-scale rollout of IEMFCs. The ECs devised in our research laboratory are aimed at addressing all of these issues with materials exhibiting a number of unique features, as follows. (i) Active sites with either an intrinsic ORR kinetics much improved above the Pt baseline or completely “Pt-free”, consisting of an “active metal” (e.g., Pt, Fe) whose performance is boosted by one or more “co-catalyst” (e.g., Co, Ni, Cu, Sn). (ii) Strong, covalent interactions between the active sites and the C-/N- ligands of the “coordination nests” on the surface of the EC support, warranting a high durability. (iii) A support featuring a “core-shell” morphology, wherein a “core” consisting of suitable carbon system(s) is covered by a carbon nitride (CN) “shell”, bestowing facile charge and mass transport features (Figure 1(a)). The resulting ECs bestow the IEMFC a high performance with a minimized loading of Pt. Specifically, the PEMFC prototypes mounting the ECs here described yielded more than 20 kW∙gPt -1.The second main topic of this overview is the development and the study of the conductivity mechanism of separator membranes for IEMFCs. The latter consist mainly of ionomer matrices (e.g., perfluorinated systems such as Nafion™, SPEEK and developmental anion-exchange block copolymers), both pristine and doped with suitable nanofillers (e.g., conventional ceramic oxoclusters, “core-shell” oxocluters, among many others). The matrix-nanofiller interactions modulate the physicochemical features of the resulting hybrid inorganic-organic membrane, allowing to improve crucial features for applications in IEMFCs such as: (i) mechanical stability; and (ii) conductivity in dry conditions and high temperature. Other separator membranes are overviewed, including: (i) anion-exchange ionomers based on polyketone matrices (Figure 1(b)); (ii) hybrid inorganic-organic membranes for HT-PEMFCs based on oxocluster nanofillers and polybenzimidazole-like matrices; and (iii) membranes swollen with proton-conducting ionic liquids. These membranes underwent a thorough characterization elucidating their morphology, structure, thermal properties, thermomechanical relaxations and electric response (Figure 1(c)). The integration of all the above knowledges yielded a unique, comprehensive and general framework which proved crucial to elucidate the interplay between the physicochemical properties of the different phases within each membrane and their overall conductivity mechanism. This allowed to trigger the development of new high-performing separator membranes for application in IEMFCs. Figure 1

Differentiating the dominant intrinsic kinetics for lithium dendrite growth under different circumstances by computational study

Although many works have been devoted to designing the dendrite-suppression lithium anodes through modifying the growth environments or electrode configurations, studies on their related intrinsic kinetics processes are still lacking. Using DFT calculations, the intrinsic kinetics processes to control the dendrite growth in different environments are investigated herein. Under different coverage concentrations and distributions of lithium, three types of competitive kinetics processes have been identified and defined as the two-dimensional (2D) accumulation, 2D dispersion, and 3D accumulation kinetics processes based on the near-neighboring interactions in the same layer. It was found that the dendrite-free condition can be realized under the natural growth processes based on the dominant 2D accumulation processes, but the dominant kinetics processes can be replaced by the 3D accumulation processes during the nonuniform deposition processes under the condition of moderate coverage concentration, leading to the formation of dendrites. Correspondingly, the suppression condition for the dendrite growth requires that the 2D dispersion kinetics processes can triumph over the 3D accumulation kinetics processes. Therefore, we employed the lithium-affinity molecules to illustrate how to adjust the 2D dispersion kinetics processes to suppress dendrite growth. These results provide microscopic guidance suppressing dendrite growth.