High Activation Energy Research Articles

Machine Learning in Predicting Activation Barrier Energy of C=N Bond Rotation in Amides

This study applies machine learning (ML) to predict activation energy barriers for cis‐trans isomerization in twisted amides, focusing on the C=N bond. Amides are increasingly used in synthetic chemistry, particularly in cross‐coupling reactions, due to their versatility. However, the C=N bond’s high activation energy presents a challenge. Using Density Functional Theory (DFT) calculations, the study evaluates key structural parameters and energy barriers for different amides. ML models, including support vector regression and neural networks, are developed to predict these activation barriers based on molecular descriptors. The results show that twisted amides, particularly N‐Ts and N‐Boc types, exhibit unique reactivities influenced by steric and electronic factors. The neural network model outperformed other methods with R2 values of around or over 0.9 for ΔG‡ and ΔGtrans, though overfitting remains a concern. These findings contribute to a deeper understanding of amide reactivity, facilitating the design of more efficient catalytic systems.

Strain-Controlled Thermal–Mechanical Fatigue Behavior and Microstructural Evolution Mechanism of the Novel Cr-Mo-V Hot-Work Die Steel

In response to the intensifying competition in the mold market and the increasingly stringent specifications of die forgings, the existing 55NiCrMoV7 (MES 1 steel) material can no longer meet the elevated demands of customers. Consequently, this study systematically optimizes the alloy composition of MES 1 steel by precisely adjusting the molybdenum (Mo) and vanadium (V) contents. The primary objective is to significantly enhance the microstructure and thermal–mechanical fatigue performance of the steel, thereby developing a high-performance, long-life hot working die steel designated as MES 2 steel. The thermal–mechanical fatigue (TMF) tests of two test steels were conducted in reverse mechanical strain control at 0.6% and 1.0% strain levels by a TMF servo-hydraulic testing system (MTS). The microstructures of the two steels were characterized using scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), and transmission electron microscopy (TEM). The results indicate that throughout the entire thermomechanical fatigue cycle, both steels exhibit initial hardening during the low-temperature half-cycle (tension half-cycle) and subsequent continuous softening during the high-temperature half-cycle (compression half-cycle). Furthermore, under the same strain condition, the cumulative cyclic softening damage of MES 1 steel is more pronounced than that of the newly developed MES 2 steel. The number, width, and length of cracks in MES 2 steel are smaller than those in MES 1 steel, and the thermomechanical fatigue life of MES 2 steel is significantly longer than that of MES 1 steel. The microstructures show that the main precipitate phase in MES 1 steel is Cr-dominated rod-shaped carbide. It presents obvious coarsening and is prone to inducing stress concentration, thus facilitating crack initiation and propagation. The precipitate phase in MES 2 steel is mainly MC carbide containing Mo and V. It has a high thermal activation energy and is dispersed in the matrix in the form of particles, pinning dislocations and grain boundaries. This effectively delays the reduction in dislocation density and grain growth, thus contributing positively to the improvement in thermomechanical fatigue performance.

Li1.6AlCl3.4S0.6: a low-cost and high-performance solid electrolyte for solid-state batteries.

Solid electrolytes (SEs) are crucial for advancing next-generation rechargeable battery technologies, but their commercial viability is partially limited by expensive precursors, unscalable synthesis, or low ionic conductivity. Lithium tetrahaloaluminates offer an economical option but exhibit low Li+ conductivities with high activation energy barriers. This study reports the synthesis of lithium aluminum chalcohalide (Li1.6AlCl3.4S0.6) using inexpensive precursors via one-step mechanochemical milling. The resulting Cl-S mixed-anion sublattice significantly improves the ionic conductivity from 0.008 mS cm-1 for LiAlCl4 to 0.18 mS cm-1 for Li1.6AlCl3.4S0.6 at 25 °C. Structural refinement of the high-resolution XRD patterns and 6Li magic-angle-spinning (MAS) NMR quantitative analysis reveals the formation of tetrahedrally-coordinated, face- and edge-shared LiCl x S y octahedra that facilitate 3D Li+ transport. Ab initio molecular dynamics (AIMD) simulations on Li1.6AlCl3.4S0.6 support an enhanced 3D network for Li+ migration with increased diffusivity. All-solid-state battery (ASSB) half-cells using Li1.6AlCl3.4S0.6 exhibit high-rate and long-term stable cycling performance. This work highlights the potential of Li1.6AlCl3.4S0.6 as a cost-effective and high-performance SE for ASSBs.

Pyrolysis kinetics and pyrolysis-generated VOC emissions characteristics of thermally aged asphalt

ABSTRACT Styrene butadiene styrene (SBS) is widely used to enhance asphalt pavement performance. When road fires occur, asphalt quickly undergoes pyrolysis, releasing toxic volatile organic compounds (VOCs) that threaten life security. Many previous studies investigate the SBS modifier’s impact on mechanical characteristics, while quite rare of them address the pyrolysis kinetics with VOC formation of the SBS-modified asphalt, particularly when they experience thermally aged process. This study has applied the thermogravimetry-mass spectrometry technique (TG-MS) and distributed activation energy model (DAEM) to address these research gaps. Our analytical results present that the thermal stability of the SBS-modified asphalt (SBSMA) is significantly promoted with 5% higher activation energy (E) than that of unmodified asphalt (UMA), mainly attributed to the heat absorption of the SBS modifier which results in a slow temperature rise of asphalt. However, the VOC emissions of SBSMA are nearly 190% higher than those of UMA, which is owing to the thermal decomposition of the SBS modifier. Besides, thermally aged asphalt emits approximately 40% fewer VOCs than fresh asphalt, indicating that the organic-compositional loss occurs during the aging process. This work provides fundamental insights into asphalt combustion and alerts designers to re-design SBS-asphalt owing to its dramatic pyrolysis-generated VOC emissions.

Impact of calcination temperature, organic additive percentages, and testing temperature on the rheological behaviour of dried sewage sludge

Abstract The main objective of the present work is to evaluate the influence of calcination pretreatment (600–1,000°C), organic additive incorporation (4% methocel, 4% amijel, and 8% starch), and testing temperature (20–60°C) on the rheological flow behaviour of dried sewage sludge and sewage sludge ashes. Besides, the dependency of sludge systems rheology on total solid content (4–15%) and methocel percentage (3–6%) was also evaluated. Furthermore, characterization techniques such as thermal gravimetric analysis-differential scanning calorimetry, X-ray fluorescence, X-ray diffraction, Brunauer–Emmett–Teller, and scanning electron microscopy were employed to investigate, respectively, the thermal decomposition, the chemical composition, the structural variations, the specific surface area, the surface morphology, and microstructure of sludges. The analysis of rheological characteristics according to best-fitting rheological models such as Herschel–Bulkley, Ostwald–de Waele, Cross, and Carreau models revealed that the yield stress (τ 0) and infinite apparent viscosity (η ∞) increase with an increase in TS or methocel percentage and decrease with increasing calcination or testing temperature. The strong impact of testing temperature concerning the reduction of the viscosity involves high activation energy (E a). This last criterion was used to compare the inter-particle strength of sludge systems.

Synthesis and Luminescence Characterization of Novel Red-Emitting Phosphors Based on Eu3+-Activated K2Sr(MoO4)2 Molybdates for w-LEDs.

In this work, trivalent europium (Eu3+) ion activated K2Sr(MoO4)2 red phosphors have been synthesized through high-temperature solid-state reaction method at 750 ℃. Detailed analysis was conducted on the phase purity, morphology, and luminescence properties of the synthesized phosphors. X-ray diffraction (XRD) confirmed the successful formation of K2Sr(MoO4)2:Eu3+ phosphors with pure phase with space group С2/c. The photoluminescence (PL) spectroscopy was used to record the excitation and emission spectrum of Eu3+ activated K2Sr(MoO4)2 phosphor. Under the excitation of 280nm, the resultant samples exhibited the characteristic emissions of Eu3+ ions corresponding to the 5D0→7FJ transitions. The optimal doping concentration of Eu3+ ions was determined to be 35mol%. Concentration quenching mechanism was identified as the interaction of near-neighbor ions. The chromaticity coordinates of K2Sr(MoO4)2:35mol%Eu3+ were (0.659, 0.340) with a corresponding high color purity of 99.8%. The prepared K2Sr(MoO4)2:35mol%Eu3+ phosphor had good thermal stability with temperature quenching temperature (T0.5 > 420K) and high activation energy (Ea = 0.267eV). The exhaustive findings from this study form the basis for advocating the application of these phosphors in light-emitting devices.

Speedy synthesis of magnetite/carbon dots for efficient chromium removal and reduction: a combined experimental and DFT approach

Abstract Magnetic carbon dots (Fe3O4/N–CQDs) was prepared by and eco-friendly and one-step microwave method using sugarcane bagasse (SB) as a starting material, and applied to remove ad reduce Cr(VI) in wastewater. The magnetization process was performed by a novel microwave method instead of the long time conventional co-precipitation method. The prepared Fe3O4/N–CQDs showed high saturated magnetization (Ms ~ 38.047 emu/g). When neat N–CQDs and Fe3O4/N–CQDs were applied to adsorb Cr(VI), the R% was slightly higher in the case of Fe3O4/N–CQDs (93.86%) compared to N–CQDs (91.73%). Moreover, the reduction rate of Cr(VI) by Fe3O4/N–CQDs was higher than the N–CQDs. The study confirmed the presence of magnetic iron oxide (Fe-O) in the N–CQDs at 655 cm−1 using FTIR spectroscopy. Interestingly, XRD analysis revealed peaks indicative of elemental iron (Fe(0)) alongside the iron oxide. Furthermore, TGA/DTG analysis showed a significantly higher weight residue (∑RW) for Fe3O4/N–CQDs compared to N–CQDs alone, suggesting enhanced thermal stability due to the Fe3O4 component. This stability is further supported by higher activation energy (∑A) and pre-exponential factor (∑s) obtained for Fe3O4/N–CQDs compared to N–CQDs. The prepared Fe3O4/N–CQDs showed higher fluorescence compared to the N–CQDs, which make them suitable as a chemosensor for the future work. In addition, DFT calculations confirmed the high stability of the Fe3O4/N–CQDs compared to N–CQDs. Graphical Abstract

Decelerating and Accelerating Sulfur Reduction Reaction via P-OV-In2O3 Enables High-Performance Li-S Batteries.

The sluggish sulfur reduction reaction (SRR) kinetics of lithium-sulfur (Li-S) batteries seriously limits the development of Li-S batteries. The initial reduction of solid (S8) to liquid (soluble Li2Sn (4≤n≤8)) is relatively easy due to the low activation energy, whereas the subsequent conversion of liquid (soluble Li2Sn) to solid (insoluble Li2S2/Li2S) has much higher activation energy, which leads to the accumulation of Li2Sn and exacerbates the shuttle effect of Li2Sn. Therefore, establishing one selective catalyst that decelerates the previous solid-liquid reaction and accelerates the subsequent liquid-solid reaction is essential for rational tailoring of the SRR for improved performance of Li-S batteries, but it represents a daunting challenge. Here, considering that the indium oxide catalyst possesses selective catalytic properties and drawing inspiration from the theoretical calculations, In2O3 nanospheres containing phosphorus doping and oxygen vacancies (P-OV-In2O3 NSs) are designed and synthesized as a selective catalyst for Li-S batteries. Contributed by the unique selective catalytic capability, the batteries using P-OV-In2O3 NSs modified separators exhibit excellent sulfur utilization, superb rate performance (656mAhg-1 at 5.0C), and low-capacity decay rate of about 0.069% per cycle over 500 cycles at 1.0C.

Using Near‐Infrared Irradiation for Heating Mechanochemical Reactions in Organic‐Dye‐Doped Epoxy Milling Jars

AbstractAlbeit mechanochemistry is a novel promising technology that gives access to reactivity under solvent‐free conditions, heating such reactions is sometimes compulsory to obtain satisfactory results in terms of conversion, selectivity and/or yield. In this work, we developed a novel approach using a dye that absorbs NIR photons and release the energy as heat. Hence, de novo milling jars in epoxy resin doped with the dye were thus produced to obtain reactors that would produce heat upon irradiation at 850 nm. Temperature profiles were recorded, depending on the irradiance, dye charge in the resin, and milling frequency, showing an excellent control of the temperature. The usefulness of the heating jar was then demonstrated in mechanochemical reactions that are known to require heat to yield the desired product, namely Diels–Alder reactions with high activation energies and the newly developed rearrangement of a sydnone into corresponding 1,3,4‐oxadiazolin‐2‐one.

Using Near-Infrared Irradiation for Heating Mechanochemical Reactions in Organic-Dye-Doped Epoxy Milling Jars.

Albeit mechanochemistry is a novel promising technology that gives access to reactivity under solvent-free conditions, heating such reactions is sometimes compulsory to obtain satisfactory results in terms of conversion, selectivity and/or yield. In this work, we developed a novel approach using a dye that absorbs NIR photons and release the energy as heat. Hence, de novo milling jars in epoxy resin doped with the dye were thus produced to obtain reactors that would produce heat upon irradiation at 850 nm. Temperature profiles were recorded, depending on the irradiance, dye charge in the resin, and milling frequency, showing an excellent control of the temperature. The usefulness of the heating jar was then demonstrated in mechanochemical reactions that are known to require heat to yield the desired product, namely Diels-Alder reactions with high activation energies and the newly developed rearrangement of a sydnone into corresponding 1,3,4-oxadiazolin-2-one.

Plasma-Structured Molybdenum Oxycarbides Enabling Ultrastable Acidic Hydrogen Evolution up to 10 a cm-2

Fabricating electrocatalysts capable of stable operation at high current densities is crucial for the industrial proton exchange membrane water electrolysis. However, current catalysts suffer from high overpotentials and rapid degradation when working in acid electrolytes at high current densities. Despite these advantages, critical challenges still exist in designing efficient catalysts for HER in acidic electrolytes at high current densities: 1) Poor long-term stability. The corrosive environment of strong acids, combined with the heat and mechanical stresses from hydrogen (H2) bubble generation at high current densities, severely challenges the stability of existing catalysts, including those noble metal-based ones. Catalysts with both excellent thermodynamic stability and robust physical adhesion to substrates are required to ensure long-term stability under these harsh conditions. 2) High overpotential at large current densities. At high current densities, high activation energy is required to drive HER because of the rapidly consumed H3O+ near the catalyst surface and the blocked active sites by the high-level H2 bubble coverage at catalyst surfaces, leading to increased overpotential and reduced energy efficiency.Existing transition metal-based catalysts generally exhibit optimal activities only at low current densities (1-100 mA cm−2) with limited stability, making their operation in acidic electrolytes at industrial-level current densities (> 3 A cm−2) quite challenging. Non-equilibrium plasmas, characterized by highly energetic reactive species in a far-from-equilibrium state and the capability to operate at low temperatures, offer distinct advantages in the development and fabrication of innovative materials. The existence of non-equilibrium plasmas can significantly influence nucleation and crystal growth processes in material synthesis, facilitating thermodynamically unfavorable reactions that are difficult or impossible to achieve using conventional equilibrium thermal methods.In this paper, we report the in-situ growth of vertically standing nanoedge-enriched molybdenum oxycarbide nanosheets (MoOxCy) through plasma-enhanced chemical vapor deposition (PECVD) based on earth-abundant salts (i.e., MoO3 and NaCl) as precursors to achieve ultrahigh-throughput acidic electrocatalytic hydrogen evolution at high current densities up to 10 A cm-2. The plasma-structured nanoedge-enriched MoOxCy catalysts offer the following benefits toward HER: 1) Significantly improved long-term stability of catalysts because of the non-equilibrium plasma-engineered structures, which are kinetically unfavorable to obtain through conventional equilibrium thermal methods; 2) Strong localized electric field near the ultrasharp edges of the catalysts, enabling fast diffusion of H3O+ from the electrolyte to catalyst surface; 3) Efficient hydrogen bubble detachment from the nanoedge-enriched structure with high roughness, maintaining continuous exposure of catalytic sites to the surrounding electrolyte. Benefiting from the unique plasma-induced morphology and chemical composition, the MoOxCy exhibits outstanding HER performance with a low overpotential (η) of 415 mV at an ultrahigh current density (j) of up to 10 A cm-2 for 1,000 h in 0.5 M H2SO4. This performance leads to an ultrahigh H2 throughput of 4,477.4 L cm-2, substantially outperforming the state-of-the-art transition metal- and even noble metal-based catalysts. This work paves new avenues for the development of high-efficiency catalysts for practical industrial applications in electrocatalytic hydrogen evolution.

Pyrolysis characteristics of Camellia oleifera seeds residue in different heating regimes: Products, kinetics, and mechanism

The mechanisms, kinetics, and product evaluations of Camellia oleifera seeds residue (COSR) pyrolysis were studied using TGA-FTIR-MS, Py-GC/MS, and a fixed-bed reactor. The pyrolysis process could be divided into primary devolatilization (PDVL) and biochar refractory (BCRF) stages with low and high activation energies, respectively. The gases of CO2, H2, CH4, and H2O(g) were generated in the overall process of pyrolysis. The increase in pyrolysis temperature led to cracking of bio-oil components, especially the fatty acids (FA) and reduced bio-oil yield. The highest bio-oil yield (47.81 wt%) was obtained at 773 K. The biochar refractory stage was characterized by slow depolymerization, dehydrogenation, and deoxygenation reactions to generate more aromatic, alkynes containing compounds, and groups of -CH3, -CH2-, and -CH-. Due to the low reactivity in the biochar refractory stage, the reaction-order of pyrolysis was high (n = 5.2) when kinetic was studied by single-step reaction. In the independent pyrolysis of components model, decompositions of the 1st and 2nd components occurred in the primary devolatilization stage. Whereas, the decomposition of 3rd component corresponded to BCRF stage with similar reaction-order (n = 4.74–5.83) of model-free procedure.

Thickness-dependent structural and growth evolution in relation to dielectric relaxation behavior and correlated barrier hopping conduction mechanism in Ni0.5Co0.5Fe2O4 ferrite thin films

Ferrite thin films are explored due to their promising properties, which are essential in various advanced electronic devices. However, depositing a film with pure phase and uniform microstructure is challenging. The Ni0.5Co0.5Fe2O4ferrite thin films are deposited using pulsed laser deposition technique to explore the effect of thickness on structural properties, growth evolution, temperature-dependent dielectric behavior, and conduction mechanisms. Microstructural analysis revealed that the films are uniformly grown, exhibiting surface roughness ranging from ∼2 to 4 nm. The dielectric response, adhering to a modified Debye model, exhibited multiple relaxation processes, with notable changes in the dielectric constant and loss as film thickness increased. Impedance spectra exhibited both space charge and dipolar relaxation phenomena, corroborated by Cole-Cole and electrical modulus plots. The analysis of the imaginary electric modulus using the Kohlrausch-Williams-Watts function revealed non-Debye-type relaxation in all deposited films, characterized by thermally activated broad peaks. Conductivity decreased up to a certain film thickness, and the frequency exponent derived from Jonscher's power law suggested a correlated barrier hopping model for AC conduction. Activation energies improved with film thickness up to 125 nm, consistent with a constant energy barrier for polarons during relaxation and conduction phases. The film with 125 nm thickness exhibited the optimal dielectric properties, with the maximum dielectric constant, minimum dielectric loss, and highest activation energy. These findings highlight the potential of dense, uniformly grown films with high dielectric constants and low dielectric losses for advanced electronic device applications.

Accelerated Solid-State Electrolyte Synthesis via Reaction Equilibria Manipulation

Solid-state electrolytes enable the use of a lithium metal anode and offer higher energy density and thermal stability, making all-solid-state batteries (ASSBs) a promising next-generation battery technology. Solid-state synthesis is the main method of synthesizing solid-state electrolytes, such as ceramic garnet-type oxide electrolytes. Solid-state reactions can be challenging due to typically requiring a long time at very high temperatures to allow ion migration and overcome the high activation energy of the forward reaction, making scale-up impractical. Our research focuses on understanding the solid-state reaction mechanisms using a model material, Li6.5La3Zr1.5Ta0.5O12 (LLZTO), renowned for its high lithium-ion conductivity and compatibility with lithium metal anodes. We propose a strategy to manipulate the solid-state reaction equilibrium to expedite LLZTO formation to less than one hour. Operando X-ray diffraction (XRD) and ex-situ XRD were used to study the reaction progress and evolution formation mechanisms. Characterization of composition and electrochemical properties is conducted using inductively coupled plasma optical emission spectroscopy (ICP-OES) and various electrochemical analytical techniques. This presentation aims to elucidate the feasibility of synthesizing LLZTO materials within a shorter timeframe, offering valuable insights for expediting the synthesis of solid-state electrolytes through solid-state reactions.

Development of Composite Electrolytes Composed of La0.93Ba0.07F2.93 and a Polymer Electrolyte for Fluoride-Ion Batteries

IntroductionFluoride-ion batteries (FIBs), which based on a fluoride ion shuttle, have high theoretical energy densities surpassing Li-ion batteries.1 In particular, all-solid-state FIBs with solid electrolytes are nonflammable and provide high safety. Various fluoride-ion conductors have been reported as candidates for the solid electrolyte of FIB. The tysonite-type LaF3 doped with a few mol% BaF2 (La1-xBaxF3-x) has a wide electrochemical window and high ionic conductivity exceeding 10-5 S cm-1 in single crystal at room temperature.2 Although La1-xBaxF3-x exhibits high ionic conductivity in single crystals or sintered discs, it is reported that the conductivity of the cold pressed La1-xBaxF3-x is reduced by about two orders of magnitude due to the grain boundary resistance. One way to reduce the grain boundary resistance is to fill the gaps between La1-xBaxF3-x particles with a flexible polymer electrolyte to compensate for the fluoride-ion conduction path. In this study, we prepared composite electrolytes composed of La1-xBaxF3-x and fluoride-ion conducting polymer electrolytes and investigated its conduction mechanism.ExperimentalThe polymer electrolytes were prepared by mixing polyethylene oxide (PEO), tetramethylammonium fluoride (TMAF), and 2,4,6-triphenylboroxin (TPhBX) in a mortar, then hot pressing at 85 °C for 10 min. La0.93Ba0.07F2.93 (LBF) was synthesized from LaF3 and BaF2 by a solid-state reaction method. Powders of LaF3 and BaF2 were mixed in a molar ratio of 93:7, and milled by a ball milling. The mixture was sintered at 900 °C for 6 h in a vacuum-sealed quartz tube. The composite electrolytes were prepared by mixing LBF with PEO, TMAF, and TPhBX in a mortar and hot pressing at 85 °C for 10 min. AC impedance measurements of the polymer electrolyte and the composite electrolyte were performed using gold foil as a current collector.Results & discussionsFirst, we optimized the composition of the polymer electrolytes. Figure 1(a) shows Arrhenius plots of the polymer electrolytes prepared by the molar ratio of the ethylene oxide (EO) of PEO to TMAF at 20:1 and changing the molar ratio of TPhBX (x). The conductivity of the polymer electrolytes increased with the addition of TPhBX in the range of x = 0-0.4. This result indicates that TPhBX enhances dissociation of TMAF, resulting in an increase in charge carriers. On the other hand, the conductivity decreased at the composition of x = 0.6. To determine the optimal amount of PEO, the molar ratio of TMAF to TPhBX was at 1:0.4 and the molar ratio of EO (y) was changed to prepare the polymer electrolytes. The Arrhenius plots of the obtained polymer electrolytes were shown in Fig. 1(b). The polymer electrolyte with the composition of y = 25 was found to have the highest conductivity. From these results, the optimal composition of the polymer electrolyte was determined to be molar ratio of EO:TMAF:TPhBX = 25:1:0.4.Figure 1(c) shows the conductivity of the composite electrolytes prepared by combining LBF and the optimized polymer electrolyte at 25 ºC for various compositions. The lowest conductivity was obtained for the composite electrolyte with 40 wt% LBF content. Moreover, the composite electrolytes had lower conductivity than the polymer electrolytes and LBF at all compositions. These results were attributed to the high activation energy of the interface resistance between the polymer electrolyte and LBF, which prevents the migration of fluoride ions.Reference[1] M. A. Reddy, and M. Fichtner, J. Mater. Chem., 21 (2011) 17059.[2] A. Roos, et al., Solid State Ionics, 13 (1984) 191.AcknowledgmentThis presentation is based on results obtained from a project, JPNP21006, commissioned by the New Energy and Industrial Technology Development Organization (NEDO). Figure 1

Enhancement of Alkaline OER Performance of the Electroplated Ni-P Catalysts Using Electrochemical Dealloying Technique

With the growing attention on renewable energy, hydrogen is receiving attention as an energy carrier to resolve the temporal and spatial constraints of renewable energy. Electrical energy generated from renewable energy can be efficiently stored and transported in the form of hydrogen. Here, water electrolysis consists of two reactions, hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), and the high activation energy of OER is the main bottleneck of water electrolysis. Consequently, highly active catalysts are indispensable. Currently, the Pt- and Ir-based noble metal catalysts boast the highest performance for OER, but face significant commercialization hurdles due to their high cost.Transition metal-based compounds are promising as substitutes of Platinum group materials for OER catalysts due to their high catalytic activity and earth-abundant properties. In particular, transition metal phosphides (TMPs) such as Ni-P are receiving much attention due to its remarkable catalytic performance approaching that of Pt-based one. In Ni-P, electrons are transferred from Ni to P due to the difference in electronegativity, allowing the energy of the HER and OER intermediate to be controlled for optimal activity. Furthermore, the Ni-P synthesized through electrodeposition has high potential as a promising substitute because they can have a variety of P ratios on the N-P surface, that can significantly affect catalytic activity and improve it more. Unfortunately, however, the electrodeposited Ni-P mostly has a flat and aggregated morphology, resulting in a low surface area and hence low catalytic performance. Therefore, to maximize the catalytic performance of the electroplated Ni-P. it is necessary to increase in surface area and number of active sites as well as the optimization of surficial P ratio.In this context, we propose a morphology control method using electrochemical dealloying, which can greatly increase the surface area of the electroplated Ni-P. Specifically, under acidic conditions, a potential higher than the reduction potential of Ni causes partial dealloying of Ni on the Ni-P catalyst. Then, the partial dealloyed Ni creates defects between grains and forms a porous structure. As a result, the surface of the dealloyed Ni-P catalyst was exposed along the grain boundaries through SEM, and a quantitative increase in surface area was confirmed through cyclic voltammetry (CV). In addition, it was confirmed through XPS analysis that the bond between Ni and P became stronger, and based on this, it was confirmed that the tafel slope and TOF of the catalyst increased. The increase in overall performance of the catalyst was confirmed through the polarization curve as surface area and intrinsic activity increased. Figure 1

Evaluating Electric Double Layer Effects at Solid Electrolyte Interfaces with Field-Effect Transistor Utilizing p-Doped SiC (100) Single Crystal

All-solid-state batteries represent the promising avenue for next-generation battery technology, crucial for achieving carbon neutrality and possessing versatile applications, notably in electric vehicles. Despite growing anticipation regarding their high energy density and safety features, a significant impediment to their widespread adoption lies in the output reduction stemming from elevated interface resistance at the lithium solid electrolyte/electrode interface. Among the suspected factors contributing to this interface resistance is the electric double layer effect, induced by fluctuations in Li+ concentration near the interface. The electric double layer effect entails the accumulation of charged ions from the electrolyte at the electrode interface, generating a layer of positive or negative charge, with the opposing charge distributed onto the electrode, resulting in an overall charge distribution near the interface. The formation of an electric double layer near the electrode interface is well-documented in liquid electrolytes, but its occurrence in solid electrolyte systems, known for their possible mixed ion/electron conductivity, presents a complexity due to the participation of multiple charge carriers. Consequently, discerning the electric double layer effect of solid electrolytes becomes challenging.Our research team has developed a new method to evaluate the charge of the electric double layer on the surface of a solid electrolyte by Hall measurement, utilizing the mechanism of a field-effect transistor and the characteristics of chemically inert hydrogenated diamond[1,2]. A lithium-based solid electrolyte is used for the dielectric part of the field-effect transistor, and diamond, which does not react with Li+ and does not insert or desert ions, is used for the semiconductor part. With this structure, only the charge generated by the electric double-layer effect of the solid electrolyte could be captured as a change in the electron carrier density on the diamond surface. However, hydrogenated diamond has the disadvantage that the plasma irradiation associated with sputter deposition and heat treatment at high temperatures damage the terminated hydrogen, which limits the types of electrolytes and deposition methods.In this study, we fabricated a field-effect transistor (FET) using a highly inert SiC (100) single crystal implanted with a p-type dopant, aluminum (Figure 1). We deposit Li3PO4 (1000 nm) by the RF sputtering method at room temperature. We chose the amorphous Li3PO4 because it owns compatibility with relatively high Li+ conductivity and stability. That is the reason why the amorphous Li3PO4 is widely used as a solid electrolyte for solid-state batteries. As shown in Figure 2, the channel resistance change was confirmed by gate voltage sweep. When a positive gate voltage is applied, Li+ in the electrolyte moves towards the SiC channel. Consequently, as the holes depart from the electrolyte interface, the carrier density decreases and the channel resistance increases. In addition, hall measurements of carrier density and mobility using the SiC single crystal with doping density at 5×1018 cm-3 resulted in a hole density of 5.88×1015 cm-3 and mobility of 109 cm2/Vs at room temperature. The mobility for dopant concentration was close to the literature value of 100 cm2/Vs[3]. Regarding the hole density, the measured value was far lower than the doping density. It is reasonable by considering the relatively high activation energy of the Al acceptor in SiC (about 150-190 meV), which is considerably larger than the thermal activation energy of 25 meV. This research made it possible to evaluate the charge of the electric double layer on the solid electrolyte surface by Hall measurement for various electrolytes and deposition methods.In Summary, we fabricated FET using p-doped SiC as the channel material and conducted measurements of channel resistance change, carrier mobility, and carrier density through Hall measurements. This research enables a comprehensive assessment of the electric double-layer effect at the electrode/solid electrolyte interface, an aspect that has not been thoroughly elucidated previously. The gate voltage dependence of channel carrier density and mobility, electrolyte dependence, and the results of Hall measurements using various electrolytes, as well as methods and principles for improving the on/off ratio of FETs will be presented on the day. This work was partly supported by GteX Program Japan Grant Number JPMJGX23S2 and JST PRESTO Grant number JPMJPR23H4.[1] Tsuchiya, T. et al. The electric double layer effect and its strong suppression at Li+ solid electrolyte/hydrogenated diamond interfaces. Commun. Chem. 4, 117 (2021).[2] Takayanagi, M. et al. Accelerated/decelerated dynamics of the electric double layer at hydrogen-terminated diamond/Li+ solid electrolyte interface. Mater. Today Phys. 31, 101006 (2023).[3] Stefanakis, D. et al. TCAD models of the temperature and doping dependence of the bandgap and low field carrier mobility in 4H-SiC. Microel. Eng. 116,(2014). Figure 1

Effect of Bi Doping on the Kinetics of Nickel Oxides-Based Electrocatalyst in Alkaline Oxygen Evolution Reaction

As a generation process of hydrogen fuel, an alkaline water electrolysis is considered as one of the most promising pathway. The water electrolysis is able to divide into two half-cell reaction: hydrogen evolution reaction (HER) in cathode and oxygen evolution reaction (OER) in anode. However, high activation energy of OER is regarded as a major bottleneck for utilization of water electrolysis, therefore it is necessary to use an electrocatalyst to improve the reaction rate. Currently, commercially used electrocatalysts of OER is precious metal such as platinum (Pt), ruthenium (Ru), and iridium (Ir) based compound which have critical drawback for high cost and low stability in alkaline electrolyte.As a substitute of platinum group materials for electrocatalyst of oxygen evolution reaction (OER), the development of cost-effective and high-active nickel oxide catalyst has attracted intense research interest. Alkaline OER is composed by five states: M, M-OH, M-O, M-OOH, and M + O2, and the gibbs free energy of final state is 4.92 eV higher than the first state. Thus, the free energy difference between each states equally becomes 1.23 eV to minimize the activation energy of rate determining step (RDS). In this point, nickel oxide shows a remarkable catalytic activity because a rapid and reversible electrochemical oxidation on the surface of nickel oxide triggers reconstructions to form hydroxide which is suitable structures for intermediate of OER. However, the nickel oxide still has high activation energy of reaction step from nickel(II) oxide to nickel(III) oxyhydroxide (3rd step of OER, Ni-O à Ni-OOH), which becomes RDS of OER. Because the catalytic activity seriously reduces without the balanced rate between each step of reaction, it is necessary to control the electric structure of nickel oxide to optimize adsorption energy of intermediates.In this context, bismuth doped nickel oxide is synthesized for electrocatalyst of OER. Because bismuth has higher electronegativity than nickel, the adsorption energy of positively charged nickel with proton decreases and the adsorption energy of positively charged nickel oxide with hydroxide ion increases. Therefore, the activation energy of RDS of OER is expected to reduce than the pristine nickel oxide.In practice, the bismuth doped nickel oxide is synthesized by hydrothermal process and the composition of bismuth is controlled by the concentration of precursors. The crystal structure of nickel oxide is maintained after the addition of bismuth, but the inter-planar spacing of overall plane of nickel oxide structure decreases according to selected area electron diffraction (SAED) pattern of transmission electron microscopy (TEM). In this context, the bismuth additive does not form the bi-metal oxide with nickel, but it substitutes the nickel site of nickel oxide structure. According to the nickel 2p3/2 spectra of x-ray photoelectron spectroscopy (XPS), a binding energy of nickel oxide peak positively shifts when the composition of bismuth additive increased due to the shifted electron from nickel to bismuth atom. As electrochemical measurement for evaluation of catalytic activity, the bismuth doped nickel oxide shows 59 mV lower overpotential at 20 mA cm-2 in alkaline OER, respectively, than the nickel oxide. In particular, the addition of bismuth is especially influenced to intrinsic activity, the bismuth doped nickel oxide catalyst shows higher turnover frequency than the pristine nickel oxide although it has similar active surface area. Figure 1

Impact of Structural Motifs on the Ionic Diffusion Mechanism in Sulfide-Based Solid Electrolytes

Sulfide-based solid electrolytes, such as lithium thiophosphate (LPS) with compositions (Li2S) 𝑥 (P2S5)1− 𝑥 and lithium Germanium thiophosphate (LGPS [Li10GeP2S12]), exhibit high ionic conductivity, rendering them promising for solid-state batteries (SSBs). However, their practical application is limited due to their low electrochemical stability and grain boundary resistance. To overcome these challenges, we explore the formation of glass-ceramic phases within the lithium thiophosphate family. Our investigation centers on the mechanism of ionic diffusion in LPS (with three compositions) and LGPS (with two distinct crystal systems) in their crystalline and glass-ceramic phases. Employing ab initio molecular dynamics (AIMD) simulations, we identify and classify the structural motifs responsible for the diffusion of Li-ions. Notably, Li2P2S6 (x = 0.5) exhibits a high activation energy for diffusion, while Li7P3S11 (x = 0.7) demonstrates elevated Li-ion diffusivity in its crystalline phase. Interestingly, the transport properties do not vary with compositions suggesting that the ion mobility is independent of the underlying structural motifs present in the glass-ceramic phases of LPS. Our structural similarity analysis also reveals a similar Li environment in the glass-ceramic phase, regardless of LPS compositions. Furthermore, increasing the crystallinity in glass-ceramic Li7P3S11 increases the amount of P2S7 4- motifs, and its percolation changes the Li environment creating a conduction pathway for Li-ion diffusion. In the case of LGPS, disorder within the glass-ceramic phase significantly diminishes ion transport similar to the behavior observed in LPS. However, the tetragonal and triclinic crystal structures reveal distinct ionic diffusion mechanisms in terms of conduction pathways. Our study emphasizes the importance of structural motifs to devise the optimal strategy for designing solid electrolyte materials. Figure 1

Plasmon-Driven Selective Methane Conversion to Higher-Value Products

The conversion of methane into energy-dense products presents an opportunity to optimize the utilization of fossil fuels while reducing greenhouse gas emissions. However, this process is hindered by the high activation energy required for C-H bond cleavage. In this study, we explored the use of plasmonic catalysis to facilitate C-C coupling of methane. The excitation of gold nanoparticles with visible light created a locally enhanced electromagnetic field that induced dipoles in the nonpolar C-H bonds. This reduced the activation energy for C-H bond dissociation, enabling the conversion of methane into C2+ hydrocarbons under mild conditions without the need for strong sacrificial oxidants. Furthermore, we demonstrated the potential to modulate the selectivity of this plasmonic catalytic process by tuning the plasmon energy. Our findings show the promise of plasmonic catalysis for efficient and selective conversion of methane into valuable products.