Kinetics Of Evolution Research Articles

Palladium Nanocubes with {100} Facets for Hydrogen Evolution Reaction: Synthesis, Experiment and Theory.

Spatially separated palladium nanocubes (Pd NCs) terminated by {100} facets are synthesized using direct micelles approach. The stepwise seed-mediated growth of Pd NCs is applied for the first time. The resulting Pd NCs are thoroughly characterized by HR-TEM, XPS, Raman, ATR-FTIR, TGA, and STEM-EDX spectroscopies. Some traces of residual stabilizer (polyvinylpyrrolidone, PVP) attached to the vertices of Pd NCs are identified after the necessary separation-washing procedure, however, it is vital to avoid aggregation of the NCs. Pd NCs are subsequently and uniformly loaded on Vulcan carbon (≈20 wt.%) for the electrochemical hydrogen cycling. By post-mortem characterizations, it is revealed that their shape and size remained very stable after all electrochemical experiments. However, a strong effect of the NCs size on their hydrogen interaction is revealed. Hydrogen absorption capacity, measured as the H:Pd ratio, ranges from 0.28 to 0.48, while hydrogen evolution and oxidation reactions (HER and HOR) kinetics decrease from 15.5 to 4.6mA.mg Pd -1 between ≈15 and 34nm of Pd NCs, respectively. Theoretical calculations further reveal that adsorption of H atoms and their penetration into the Pd lattice tailors the NCs electronic structure, which in turn controls the kinetics of HER, experimentally observed by the electrochemical tests. This work may pave the way to the design of highly active electrocatalysts for efficient HER stable for a long reactive time. In particular, obtained results might be transferred to active Pd-alloy-based NCs terminated by {100} facets.

Kinetic evolution of plasma biomarkers in acid sphingomyelinase deficiency patients under enzyme replacement therapy: A French experience

Kinetic evolution of plasma biomarkers in acid sphingomyelinase deficiency patients under enzyme replacement therapy: A French experience

Platinum-Nickel Oxide Cluster-Cluster Heterostructure Enabling Fast Hydrogen Evolution for Anion Exchange Membrane Water Electrolyzers.

Carbon black has been extensively employed as the support for noble metal catalysts for electrocatalysis applications. However, the nearly catalytic inertness and weak interaction with metal species of carbon black are two major obstacles that hinder the further improvement of the catalytic performance. Herein, we report a surface functionalization strategy by decorating transition metal oxide clusters on the commercial carbon black to offer specific catalytic activity and enhanced interaction with metal species. In the case of NiOx cluster-decorated carbon black, a strongly coupled cluster-cluster heterostructure consisting of Pt clusters and NiOx clusters (Pt-NiOx/C) is formed and delivers greatly enhanced alkaline hydrogen evolution kinetics. The NiOx clusters can not only accelerate the hydrogen evolution process as the co-catalyst, but also optimize the adsorption of H intermediates on Pt and stabilize the Pt clusters. Notably, the anion exchange membrane water electrolyzer with Pt-NiOx/C as the cathode catalyst (with a loading of only 50 μgPt cm-2) delivers the most competitive electrochemical performance reported to date, requiring only 1.90 V to reach a current density of 2 A cm-2. The results demonstrate the significance of surface functionalization of carbonaceous supports toward the development of advanced electrocatalysts.

Carbothermal Shock Synthesis of Lattice Oxygen-Mediated High-Entropy FeCoNiCuMo-O Electrocatalyst with a Fast Kinetic, High Efficiency, and Stable Oxygen Evolution Reaction.

Efficient oxygen evolution reaction (OER) catalysts with fast kinetics, high efficiency, and stability are essential for scalable green production of hydrogen. The rational design and fabrication of catalysts play a decisive role in their catalytic behavior. This work presents a high-entropy catalyst, FeCoNiCuMo-O, synthesized via carbothermal shock. Synergistic optimization of the adsorption evolution mechanism (AEM) and lattice oxygen mechanism (LOM) was realized and demonstrated through the combination of in situ spectra/mass spectrometry and chemical probe analysis in FeCoNiCuMo-O. Furthermore, the robust stability is reinforced by the inherent properties conferred by the high-entropy design. The catalyst exhibits outstanding performance metrics, featuring an exceptionally low Tafel slope of 41 mV dec-1, a low overpotential of 272 mV at 10 mA cm-2, and a commendable endurance (a mere 2.2% voltage decline after a 240-h continuous chronopotentiometry test at 10 mA cm-2). This study advances the development of efficient, durable OER electrocatalysts for sustainable hydrogen production.

Lattice-mismatched MOF-on-MOF nanosheets with rich oxygen vacancies show fast oxygen evolution kinetics for large-current water splitting

Lattice-mismatched MOF-on-MOF nanosheets with rich oxygen vacancies show fast oxygen evolution kinetics for large-current water splitting

A nonequilibrium kinetic model of high-resolution vibrational energy transfer in RDX from selective IR excitation.

In this paper, we develop a model based on a second quantization-with anharmonic phonon scattering and the phonon Boltzmann transport equation-to study precise high-resolution nonequilibrium vibrational energy transfer (VET) under selective phonon excitation in cyclotrimethylene trinitramine. We simulate mid-infrared pump-probe spectroscopy and observe a prompt appearance (<1ps) of broad-spectrum intensity, which agrees well with experimental data in the literature. The selective excitation of phonons at different frequencies reveals distinct VET pathways and the kinetic evolution of mode occupations as the system reaches a new equilibrium temperature. Three types of transition mechanisms are found to play outsized roles in terms of the amount of energy transferred and the transfer rate: (1) vibrational modes close to the excited frequencies typically respond faster and reach higher temperatures regardless of the excitation frequency; (2) the overtone pathway connecting the modes near 550 and 1150cm-1 is an important bridge between far- and mid-IR; and (3) fast aggregation of energy at 2800cm-1 mediates transfer to/from high frequencies through a second overtone pathway involving modes near 1400cm-1. In addition, by monitoring the temperature of the N-N/N-O stretching modes, strong coupling between those modes and the C-H stretching modes is found. The coupling likely draws the vibrational modes close to both the proton transfer transition state for HONO elimination and the N-N stretching for bond cleavage. The high-resolution understanding of the nonequilibrium kinetics of phonons provides important insight into the energy transfer and initiation mechanisms of molecular solids due to external stimuli.

Microstructural evolution and precipitation kinetics of carbides in L-PBF processed Inconel 718 during long-term homogenization

Microstructural evolution and precipitation kinetics of carbides in L-PBF processed Inconel 718 during long-term homogenization

C4-like metabolism and HCO3− use in submerged leaves of Ottelia cordata lacking Kranz anatomy at both low and high CO2 concentrations

To date, only a few submerged plants have been reported to perform C4 and CAM. Ottelia cordata is a heteroblastic aquatic plant developing both submerged and floating leaves throughout its life cycle. Previous research found that, besides HCO3− use, the submerged leaves of O. cordata can also perform C4 metabolism. However, it remains unclear how the HCO3− use or the C4 pathway, and the anatomical structure, respond to varying CO2 environments. Therefore, we examined the anatomical structures and carbon-concentrating mechanisms in O. cordata submerged leaves under high (HC) and low CO2 (LC) conditions. Our results revealed the leaf consists of an upper and lower layer of epidermal cells, separated by large air spaces and two layers of mesophyll cells, without the presence of Kranz anatomy. Both epidermal and mesophyll cells contained chloroplasts, but starch grains were larger in the mesophyll chloroplasts than in the epidermal cells. Additionally, the area of the upper epidermal cells, mesophyll cells, air spaces, chloroplast, and starch grains significantly increased under HC. Moreover, the ability to utilize HCO3− was stronger under LC. The activity of photosynthetic enzymes, kinetics of O2 evolution, and δ13C confirmed the C4 pathway under both HC and LC. However, the organic acid results indicated that CAM was not operational in either HC or LC. In summary, our findings suggested that the ability to use HCO3− and a C4-like metabolism may occur in the submerged leaves of O. cordata, despite the absence of Kranz anatomy, across both HC and LC environments.

Microstructure and kinetic evolutions of multi-variants lamella in γ-TiAl alloys

The D019-α2 / L10-γ alternate lamellae microstructure in TiAl alloys brings the superior mechanical property, the lamellae with multi-variant γ phase are key characteristic of morphology-property causality. The nucleation, growth and coarsening of multi-variants γ are investigated in TiAl alloys by using the three-dimensional phase-field simulation, the γ morphology, lamellar spacing (LS) and the predicted yield strength of alloy are in agreement with the experiment. It is found that the γ variants can nucleate and grow up separately to form the single-variant lamella, or through the symbiotic nucleation and growth to form multi-variant lamella, the growth of γ lamella follows the terrace-ledge-kink mechanism. The growth rate along the longitudinal direction is distinctly larger than that of the thickness direction, resulting in the lamellar structure. A three-stage growth kinetics, nucleation, growth and coarsening of γ lamella in thickness is revealed. As Al content changes, the LS is enlarged with the reduced lamella number. The influence of the LS on the mechanical properties is evaluated by using the Hall-Petch relationship. The results give an insight for the formation and evolution mechanisms of multi-variant γ lamella, and discover the internal relations of lamellar morphology and mechanical properties of TiAl alloys.

Impact of Double Layer on Electrochemical Kinetics via Bottom up Multiscale Modeling Approach

Electric double layers (EDLs) play a fundamental role in various electrochemical processes such as colloidal dispersions, surface charging, and charge-transfer reactions. Increasingly, the role of EDLs on reaction kinetics is being studied[1], revealing their importance in predicting the intrinsic and electrolyte-dependent kinetics of electrochemical reactions. Despite the extensive history of EDL modeling, there remain challenges in predicting the impact of EDL structure on reaction kinetics. The characteristic length of EDL for non-dilute solutions (typically 10 – 100 nanometers) exceeds the grasp of regular ab initio molecular dynamics (AIMD) simulations. While continuum models offer a means to estimate the quasi-equilibrium structure of EDLs with substantially lower computational cost than molecular dynamics, conventional continuum models require parameter fitting[2] due to their lack of appropriate expressions for microscopic interactions. Furthermore, the lack of a commonly accepted micro-kinetic model to evaluate the role of the EDL structure on the reaction kinetics prevents the optimization of the interface for improved reaction rates.In this talk, we propose a novel modeling framework for analyzing micro-kinetics that accounts for the contributions of EDL structure by leveraging our recently developed continuum EDL model [3] and density functional theory (DFT) calculations. Our previous work showed that the continuum model can accurately predict differential capacitance for EDL charging without necessitating parameter-fitting by incorporating microscopic interactions such as electron spillover, entropy due to solute size variation, and polarization of solvent and solute molecules [3]. We refine the continuum EDL model to account for the interactions between adsorbate coverage and EDL structure. This model utilizes DFT results, i.e., free energies and charge distributions of the adsorbates at potential of zero charge, as input properties. The model calculates the adsorbates’ coverage to minimize the total grand potential, while accounting for both the effect of electrostatic potential on the adsorbate free energy and the effect of adsorbate charge density on the electrostatic potential simultaneously. The transition state of the rate determining step is treated as an adsorbate species, with its coverage evaluated in the same manner as the other adsorbates, which is used to evaluate the reaction rate based on transition state theory. This model framework enables us to evaluate the intrinsic and electrolyte-dependent kinetic activity with reasonable computational resources. Finally, we apply this model to investigate the kinetics of hydrogen evolution and oxidation reactions (HER/HOR) having favorable comparisons with measured cation- and pH- dependent kinetics[4]. The results suggest that the charge distribution of the transition state can significantly affect electrolyte-dependent kinetics of electrochemical reactions, highlighting the importance of further analyzing the effects of EDL structures on reaction kinetics. Acknowledgements: This work was partially supported by the by the Center for Ionomer-based Water Electrolysis (CIWE), a DOE sponsored Energy Earthshot Research Center under contract number DE-AC02-05CH11231, and by a CRADA with Toyota Central R&D Labs., Inc. Part of this work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. The authors acknowledge the HydroGen Energy Materials Network from the Department of Energy, Hydrogen and Fuel Cell Technologies Office for funding under Contract numbers DE-AC02-05CH11231. Reference: [1] Shin, S.J., et al., On the importance of the electric double layer structure in aqueous electrocatalysis. Nat Commun, 2022. 13(1): p. 174.[2] Huang, J., Density-Potential Functional Theory of Electrochemical Double Layers: Calibration on the Ag(111)-KPF(6) System and Parametric Analysis. J Chem Theory Comput, 2023. 19(3): p. 1003-1013.[3] Shibata, M., S., et al., Parameter-fitting-free Continuum Modeling of Electrical Double Layer in Aqueous Electrolyte, Submitted.[4] Huang, B., et al., Cation- and pH-Dependent Hydrogen Evolution and Oxidation Reaction Kinetics. JACS Au, 2021. 1(10): p. 1674-1687. Figure 1

Discovering the Catalytic Role of Interfacial Water Towards Hydrogen Evolution/Oxidation Reactions in Aqueous Solutions

Despite significant research efforts, the sluggish kinetics of the hydrogen evolution and oxidation reactions (HER/HOR) on Pt in alkaline solutions remain poorly understood. The role of interfacial water molecules has been investigated in recent years, yet several questions persist. These include a clear definition of interfacial water molecules, their distinction from bulk or hydrated water, and their specific mechanism of action in HER/HOR processes. Addressing these questions is critical for unraveling the HER/HOR interface and will inform the development of next-generation catalysts for green hydrogen. Herein, we explore the HER/HOR kinetics of various catalysts, including monometallic (Pt, Ru, Pd) and bimetallic (Pt-Ru) systems, in alkaline electrolytes (AMOH, where AM represents alkali metal cations) at different pH levels. Our findings indicate that HER/HOR kinetics are consistently slower in 0.01M AMOH (pH 12) than in 0.1M AMOH (pH 13), a trend that current pH-based theories do not explain. Using high energy resolution fluorescence detection X-ray absorption spectroscopy (HERFD-XAS) and attenuated total reflectance-surface enhanced infrared adsorption spectroscopy (ATR-SEIRAS), we identified two distinct behaviors of interfacial water across the catalysts. In dilute electrolytes (0.01M), the interfacial water demonstrates reduced flexibility, hindering the transport of HER/HOR intermediates. Conversely, in concentrated electrolytes (0.1M), interfacial water supports the HER/HOR process via a bifunctional pathway and obey the hard-soft acid-base (HASB) interaction. Slow-growth sampling coupled with ab initio molecular dynamics (SG-AIMD) simulations corroborate that the hydrogen bonding network in 0.01M electrolyte is less conducive to reactivity compared to that in 0.1M electrolyte. Our results aid existing theories and provide new insights into the fundamental mechanisms of alkaline HER/HOR catalysis. Acknowledgement The authors thank the funding source from Liquid Sunlight Alliance under the U.S. DOE, Office of Science, Office of Basic Energy Sciences, Fuels Award Number DE-SC0021266 and the Laboratory Directed Research and Development Program of the Lawrence Berkeley National Laboratory under the U.S. DOE Contract No. DE-AC02-05CH11231. This research used beamline 8-ID (ISS) of the National Synchrotron Light Source II, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Brookhaven National Laboratory under Contract No. DE-SC0012704.

Theoretical Studies of Hydrogen Evolution Involving Imidazolium Proton Donors

The hydrogen evolution reaction (HER) is an important electrocatalytic reaction used for the electrochemical production of hydrogen gas. Its reverse reaction, the hydrogen oxidation reaction, is used to produce protons used in electrocatalytic reduction reactions for various electrochemical energy conversion and storage applications. While many fundamental studies have analyzed interfacial reactivity in aqueous HER, analogous mechanistic understanding of HER reactivity in nonaqueous media remains limited.In this presentation, periodic density functional theory (DFT) calculations are applied to mechanistic studies of HER on Pt(111) using various imidazolium proton donors. These studies incorporate analyses of imidazole adsorption and potential-dependent activation energies. The conjugate bases of imidazole adsorb strongly to the electrode surface. Yet, the adsorption geometries and energetics are sensitive to substituent effects and isomeric configurations at the interface. The potential-dependent binding geometries and adsorption energies of different imidazoles adsorbed to Pt(111) are analyzed in a dielectric continuum implicit solvent. These calculations demonstrate how imidazole derivatization and electrode surface charge impact the adsorption of imidazole conjugate bases during HER. To gain insights into the kinetics of the elementary Volmer and Heyrovsky steps of HER, potential-dependent reaction energies and activation barriers were calculated using the charge extrapolation method. Energetics were calculated for different electrode potentials by modifying the coverage of protons. This approach was used to develop relationships between reaction thermodynamics and kinetics via Brønsted–Evans–Polanyi relationships for various imidazoles, where this relationship gives charge transfer coefficients in the Butler–Volmer equation. The goal of assessing these reaction parameters is to enhance understanding of charge transfer processes and molecular interactions at the electrode-electrolyte interface, which is essential for the design of high-efficiency energy conversion and storage devices. The potential-dependent adsorption behavior and kinetics of elementary proton-coupled electron transfer steps are used to understand the reaction kinetics of hydrogen evolution in a nonaqueous imidazole-based electrolyte through comparisons to voltammetry measurements. Through these analyses, we identify kinetic trends across functionalized imidazoles, providing valuable perspectives for the development of catalytic systems and energy storage technologies.

Ionomer Impact on Oxygen Evolution Reaction Activity and Kinetics for Ir-Based Catalysts

Renewable hydrogen generation using the low-temperature proton-exchange membrane water electrolyzer (PEMWE) represents a crucial technology for achieving global zero-carbon emissions. Iridium oxide (IrOx) stands out as a primary platinum group metal catalyst for the anode in electrochemical water splitting due to a balance in activity and stability in acidic environments.1 However, the anode catalyst performance is still predominately hampered by the sluggish kinetics of the oxygen evolution reaction (OER) compared to the hydrogen evolution reaction (HER) at the Pt cathode.2 Therefore,understanding the factors influencing the OER kinetics of Ir-based catalysts is essential for developing strategies to achieve high OER activity in the PEMWE anode electrocatalysts. This presentation will delve into our investigation of how the perfluorosulfonic acid (PFSA) binder affects the anode catalyst OER behaviors, specifically the corresponding kinetics and activity of two commercial Ir-based OER catalysts, IrOx from Alfa Aesar and TiO2-decorated IrOx (IrTiOx) from Umicore, as a function of the PFSA ionomer-to-catalyst (I/C) ratio. We combined the cavity microelectrode (CME) technique, which offers a direct approach to study OER kinetics without the ionomer,3 with the rotating disc electrode (RDE) technique, which allows to assess the impact of PFSA on OER kinetics and activity at varied I/C ratios in an acidic electrolyte. The study provided valuable insights into ionomer dependent OER mechanisms, elucidating the intricate interactions among the ionomer, catalyst, and reaction intermediates.AcknowledgementsThis research is supported by the U.S. Department of Energy, Energy Efficiency and Renewable Energy, Hydrogen and Fuel Cell Technologies Office under the auspices of the H2NEW Consortium. Argonne National Laboratory is managed by the U.S Department of Energy by the University of Chicago Argonne, LLC, also under contract DE-AC-02-06CH11357.Reference S. M. Alia, M.-A. Ha, G. C. Anderson, C. Ngo, S. Pylypenko and R. E. Larsen, Journal of The Electrochemical Society, 2019, 166, F1243.E. Oakton, D. Lebedev, M. Povia, D. F. Abbott, E. Fabbri, A. Fedorov, M. Nachtegaal, C. Copéret and T. J. Schmidt, Acs Catalysis, 2017, 7, 2346-2352.J. Behnken, M. Yu, X. Deng, H. Tüysüz, C. Harms, A. Dyck and G. Wittstock, ChemElectroChem, 2019, 6, 3460-3467.

Sustainable Semi-Continuous Rare Earth Alloy Production in Chloride Based Molten Salts

Rare earth elements have numerous uses ranging from green energy to defense applications. Nd metal production uses a neodymium/lithium fluoride molten salt with a consumable carbon anode where dissolved neodymium oxide and carbon are converted to neodymium metal and CO2. In addition to producing CO2, the process releases PFCs, making it environmentally unsustainable. We have shown that neodymium chloride can be electrolyzed to produce Nd metal at the cathode and chlorine gas at the anode. The chlorine can be recycled in the conversion of the neodymium oxide (from ore) to neodymium chloride. In our process, the anode is non-consumable which allows for continuous processing without producing deleterious greenhouse gases. Chloride rare earth electrowinning historically suffered from low Coulombic efficiency obtained in lab-scale efforts (10-50%). The electrolytic reduction of neodymium chloride is a two-step reaction where a stable intermediate (Nd2+) is formed,1-2 The intermediate species can diffuse away from the cathode resulting in efficiency losses. Further, anodic overpotentials for the chlorine evolution reaction are significant due to the somewhat sluggish kinetics and poor wetting characteristics of the salt on traditional graphite anodes. Solid metal electrowinning in molten salts tends to produce rough deposits which trap significant salt impurities necessitating downstream purification. However, producing liquid metal allows for easy density separation from the salt, leading to a purer as-deposited product as well as faster metal deposition kinetics (i0 ~ 1 A/cm2) which reduces the effects of Nd2+ out diffusion, and chlorine evolution kinetics (i0 ~ 0.2 A/cm2) because of the higher temperature. In this talk, we report our work on improvements to Coulombic efficiency (~85%), and a stable anode that catalyzes chlorine evolution. The combination of improved Coulombic efficiency and reduced anode overpotentials results in low specific energy consumption (~3 kWh/kg) and thus lower operating costs. We will also report on efforts to produce liquid metal in the form of an NdFe alloy at ~800 °C which can be collected semi-continuously at rates of >1 A/cm2. References : R. Akolkar, J. Electrochem. Soc., 169, 043501 (2022). D. Shen and R. Akolkar, J. Electrochem. Soc., 164, H5292–H5298 (2017). Holcombe et al., ACS Sustainable Chem. Eng. 2024, 12, 10, 4186–4193, (2024). Holcombe et al., Holcombe et al 2024 Electrochem. Soc. Interface 33 49, (2024). Rohan Akolkar. System and Process for Sustainable Electrowinning of Metals. US Patent 20230279572. Sept. 2023 Portions of this work were performed by LLNL under Contract DE-AC52-07NA27344.

Operando Spectroscopic Investigation of the Re2O7.2H2O Adduct obtained by Controlled Hydration of Re2O7.

We provide here a comprehensive investigation spectroscopic of the controlled hydration of Re2O7 using Raman, Fourier-Transform Infrared (FTIR) and X-Rays Absorption (XAS) techniques in complement with ab initio modelling for confirming the spectral assignments. Hence, the Raman signature of Re2O7.2H2O was obtained, and the evolution kinetics was investigated to provide a detailed description of the hydration process.

Enhancement of BiVO4 photoanode surface oxygen evolution kinetics via Ni-Fe-ZIF derived bimetallic NiFeOx co-catalyst for water oxidation

The water oxidation kinetics on the surface of bismuth vanadate (BiVO4) photoanode is slow and the surface charge recombination is serious which hindering the photoelectrochemical (PEC) water splitting process. To enhance the PEC performance of BiVO4 and expedite the water oxidation process, in this work, a straightforward electrostatic adsorption and pyrolysis methods were devised to convert bimetallic Ni-Fe-zeolitic imidazolate frameworks (Ni-Fe-ZIF) molecular sieve into NiFeOx oxygen evolution co-catalyst and modified on BiVO4 photoanode surface (NiFeOx/BiVO4). The optimized NiFeOx/BiVO4 photoanode showed a high optical photocurrent density of 3.57 mA/cm2 at 1.23 V compared with reversible hydrogen electrode under AM 1.5G illumination with 4.4 times compared to the pure BiVO4 photoanode. The NiFeOx/BiVO4 composites photoanodes also exhibited the higher charge transfer efficiency of more than 77.8 % than the pure BiVO4 photoanode, indicating that the NiFeOx has excellent co-catalytic properties during PEC process. The improvement of photoelectric conversion efficiency can be attributed to the presence of NiFeOx layer with oxygen vacancies and more metal active sites on the BiVO4 surface which promoted the separation and transport of photoelectron-hole pairs and the surface oxygen evolution kinetics, thus significantly improving the photocurrent density.

Multiscale Modeling of Nanoparticle Precipitation in Oxide Dispersion-Strengthened Steels Produced by Laser Powder Bed Fusion.

Laser Powder Bed Fusion (LPBF) enables the efficient production of near-net-shape oxide dispersion-strengthened (ODS) alloys, which possess superior mechanical properties due to oxide nanoparticles (e.g., yttrium oxide, Y-O, and yttrium-titanium oxide, Y-Ti-O) embedded in the alloy matrix. To better understand the precipitation mechanisms of the oxide nanoparticles and predict their size distribution under LPBF conditions, we developed an innovative physics-based multiscale modeling strategy that incorporates multiple computational approaches. These include a finite volume method model (Flow3D) to analyze the temperature field and cooling rate of the melt pool during the LPBF process, a density functional theory model to calculate the binding energy of Y-O particles and the temperature-dependent diffusivities of Y and O in molten 316L stainless steel (SS), and a cluster dynamics model to evaluate the kinetic evolution and size distribution of Y-O nanoparticles in as-fabricated 316L SS ODS alloys. The model-predicted particle sizes exhibit good agreement with experimental measurements across various LPBF process parameters, i.e., laser power (110-220 W) and scanning speed (150-900 mm/s), demonstrating the reliability and predictive power of the modeling approach. The multiscale approach can be used to guide the future design of experimental process parameters to control oxide nanoparticle characteristics in LPBF-manufactured ODS alloys. Additionally, our approach introduces a novel strategy for understanding and modeling the thermodynamics and kinetics of precipitation in high-temperature systems, particularly molten alloys.

A reduced cluster dynamics modeling of radiation damage in tungsten

A reduced cluster dynamics model is developed to investigate the microstructure evolution of irradiated single crystal tungsten. The model accounts for the generation and reaction of point defects, small-size defect clusters, helium clusters, as well as the nucleation and growth of large immobile defects, including the interstitial dislocation loops, voids and helium bubbles. Moreover, by incorporating an atomically informed loop punching mechanism for bubble growth, the model is able to accurately capture the evolution kinetics of radiation-induced defects with and without the helium implantation. The predicted densities and sizes of loops and voids/bubbles, the helium-to-vacancy ratio and the internal pressure of helium bubbles are all in good agreement with experimental data at different irradiation doses across a wide range of temperatures from 300 K up to 1200 K. This work aims to provide a robust tool for analyzing the microstructure of irradiated tungsten under both fission and fusion conditions.

Self-Etching Synthesis of Superhydrophilic Iron-Rich Defect Heterostructure-Integrated Catalyst with Fast Oxygen Evolution Kinetics for Large-Current Water Splitting.

Developing catalysts with rich metal defects, strong hydrophilicit, and extensive grain boundaries is crucial for enhancing the kinetics of electrocatalytic water oxidation and facilitating large-current water splitting. In this study, we utilized pH-controlled etching and gas-phase phosphating to synthesize a flower-like Ni2P-FeP4-Cu3P modified nickel foam heterostructure catalyst. This catalyst features pronounced hydrophilicity and a high concentration of Fe defects. It exhibits low overpotentials of 156 mV and 210 mV at current densities of 10 and 100 mA cm-2 respectively, and maintains stability for up to 200 h at 100 mA cm-2 with only 7.3% degradation, showcasing outstanding electrocatalytic water oxidation performance. Furthermore, when integrated into a Ni2P-FeP4-Cu3P/NF||Pt-C/NF electrolyzer, it achieves excellent overall water splitting performance, reaching current densities of 10 and 400 mA cm-2 at just 1.47 V and 1.73 V, respectively, and operates stably for 60 h at 500 mA cm-2 with minimal degradation. Analysis indicates that high-valence oxyhydroxides/phosphides of Ni, Fe, and Cu act as the primary active species. The presence of abundant Fe defects enhances electron transfer, strong hydrophilicity improves electrolyte contact, and numerous grain boundaries synergistically modulate the activation energy between active sites and oxygen-containing intermediates, significantly improving the kinetics of water oxidation.

Optimizing Charge Separation and Transport: Enhanced Photoelectrochemical Water Splitting in α-Fe2O3/CZTS Nanorod Arrays

This study explores the enhancement of α-Fe2O3 (hematite) nanorod arrays for photoelec-trochemical applications by constructing a Cu2ZnSnS4 (CZTS) heterojunction. While α-Fe2O3 offers good stability, a low cost, and environmental benefits, its efficiency is limited by slow oxygen evolution kinetics, high carrier recombination rates, and low conductivity. By introducing CZTS, a material with strong light absorption and charge transport properties, we enhance the separation of photogenerated charge carriers, reduce charge transfer resistance, and increase the carrier concentration, thereby boosting the overall photoelectrochemical performance. The experimental results show that a modified FC-15 photoanode achieves a photocurrent density of 3.40 mA/cm2 at 1.60 V vs. RHE, a substantial increase compared to 0.40 mA/cm2 for unmodified α-Fe2O3. Band gap analysis reveals a reduced band gap in the FC-15 material, enhancing light absorption and boosting the photoelectrocatalytic performance. In photoelectrochemical water-splitting tests, the FC-15 photoanode achieves a hydrogen production rate of 41.6 μmol/cm2/h, which is significantly improved over the unmodified sample at 5.64 μmol/cm2/h. These findings indicate that the CZTS/α-Fe2O3 heterojunction effectively promotes charge separation, enhances charge transport, and improves light absorption, substantially increasing photocatalytic efficiency. This heterojunction approach offers new insights and technical strategies for developing photocatalytic materials with potential applications in renewable energy.