Large Density Research Articles

Enhancing the foamability of poly(L-lactide-co-ε-caprolactone) through formation of stereocomplex crystal by introducing of poly(D-lactic acid)

The bio-elastomer poly (L-lactide-co-ε-caprolactone) (PLCL) with linear random molecular chain structure exhibits low viscosity and melt strength, resulting in poor foamability, cell merging, or collapse during the foaming process. Consequently, PLCL foams have large cell sizes and low cell densities, limiting their use as biodegradable elastomeric foams. To enhance the foamability of PLCL, poly (D-lactic acid) (PDLA) was incorporated into the PLCL matrix. Stereocomplex crystals (Sc-crystals) formed between the L-LA segments of PLCL and the molecular segments of PDLA. The effects of varying PDLA content on the basic properties and foaming behavior of the blends were investigated. Results indicate that optimal Sc-crystal formation occurs in the PLCL/PDLA-10 blend. The presence of Sc-crystals enhances melt strength and facilitates cell nucleation, reducing cell size from 351.2 to 11.8 μm and increasing cell density from 1.4 × 104 to 1.7 × 108 cells/cm³. Consequently, the mechanical properties of the foam are significantly improved. The Sc-crystal formation between PLCL and PDLA provides an effective method to enhance the processability of linear chain copolymers containing L-lactide.

Outstanding energy storage properties under moderate electric field in BiMg2/3Nb1/3O3-modified NaNbO3-based relaxor ceramics

NaNbO3 (NN)-based ceramics have received a great deal of attention for the potential application in dielectric energy storage capacitors. However, the energy storage properties (ESP) remain low, particularly under moderate electric field. Herein, a Bi-rich doping unit of BiMg2/3Nb1/3O3 (BMN) was introduced into a 0.85NaNbO3-0.15Bi0.1Sr0.85TiO3 (NN-SBT) matrix, aiming to improve polarization along ESP. As a result, a large recoverable energy density (Wrec) of ∼6.1 J/cm3 and an efficiency (η) of ∼81 % were achieved in NN-SBT-0.08BMN ceramics under a moderate electric field of 337 kV/cm. The improved ESP can be attributed to the introduction of BMN, which delays the polarization saturation of NN-SBT ceramics, while maintaining the maximum polarization (∼43.6 μC/cm2), and generating polar nanoregions (PNRs). Moreover, the optimal ceramics exhibited good thermal (25–130 °C) and frequency (1–300 Hz) stabilities, and fatigue endurance (>105 cycles). These results illustrate that the designed NN-SBT-0.08BMN ceramics are promising for application in dielectric energy storage capacitors with high ESP under a moderate electric field.

Efficient point-based simulation of four-way coupled particles in turbulence at high number density.

In many natural and industrial applications, turbulent flows encompass some form of dispersed particles. Although this type of multiphase turbulent flow is omnipresent, its numerical modeling has proven to be a remarkably challenging problem. Models that fully resolve the particle phase are computationally very expensive, strongly limiting the number of particles that can be considered in practice. This warrants the need for efficient reduced order modeling of the complex system of particles in turbulence that can handle high number densities of particles. Here we present an efficient method for point-based simulation of particles in turbulence that are four-way coupled. In contrast with traditional one-way coupled simulations, where only the effect of the fluid phase on the particle phase is modeled, this method additionally captures the back-reaction of the particle phase on the fluid phase, as well as the interactions between particles themselves. We focus on the most challenging case of very light particles or bubbles, which show strong clustering in the high-vorticity regions of the fluid. This strong clustering poses numerical difficulties which are systematically treated in our work. Our method is valid in the limit of small particles with respect to the Kolmogorov scales of the flow and is able to handle very large number densities of particles. This methods paves the way for comprehensive studies of the collective effect of small particles in fluid turbulence for a multitude of applications.

Dark matter line searches with the Cherenkov Telescope Array

Monochromatic gamma-ray signals constitute a potential smoking gun signature for annihilating or decaying dark matter particles that could relatively easily be distinguished from astrophysical or instrumental backgrounds. We provide an updated assessment of the sensitivity of the Cherenkov Telescope Array (CTA) to such signals, based on observations of the Galactic centre region as well as of selected dwarf spheroidal galaxies. We find that current limits and detection prospects for dark matter masses above 300 GeV will be significantly improved, by up to an order of magnitude in the multi-TeV range. This demonstrates that CTA will set a new standard for gamma-ray astronomy also in this respect, as the world's largest and most sensitive high-energy gamma-ray observatory, in particular due to its exquisite energy resolution at TeV energies and the adopted observational strategy focussing on regions with large dark matter densities. Throughout our analysis, we use up-to-date instrument response functions, and we thoroughly model the effect of instrumental systematic uncertainties in our statistical treatment. We further present results for other potential signatures with sharp spectral features, e.g. box-shaped spectra, that would likewise very clearly point to a particle dark matter origin.

Modulating the Active Sites of VS2 by Mn Doping for Highly Selective CO2 Electroreduction to Methanol in a Flow Cell.

Methanol is a valuable liquid C1 product in CO2 electroreduction (CO2ER); however, it is hard to achieve high selectivity and a large current density simultaneously. In this work, we construct Mn2+-doped VS2 multilayer nanowafers applied in a flow cell to yield methanol as a single liquid product to tackle this challenge. Mn doping adjusts the electronic structure of VS2 and concurrently introduces sulfur vacancies, forming a critical *COB intermediate and facilitating its sequential hydrogenation to methanol. The optimal Mn4.8%-VS2 exhibits methanol Faradic efficiencies of more than 60% over a wide potential range of -0.4 to -0.8 V in a flow cell, of which the maximal value is 72.5 ± 1.1% at -0.6 V along with a partial current density of 74.3 ± 1.1 mA cm-2. This work opens an avenue to rationally design catalysts for engineering C1 intermediates toward CO2ER to a single liquid methanol in a flow cell.

Improving NiFe Electrocatalysts through Fluorination-Driven Rearrangements for Neutral Water Electrolysis.

Neutral electrolysis to produce hydrogen is prime challenging owing to the sluggish kinetics of water dissociation for the electrochemical reduction of water to molecular hydrogen. An ion-enriched electrode/electrolyte interface for electrocatalytic reactions can efficiently obtain a stable electrolysis system. Herein, we found that interfacial accumulated fluoride ions and the anchored Pt single atoms/nanoparticles in catalysts can improve hydrogen evolution reaction (HER) activity of NiFe-based hydroxide catalysts, prolonging the operating stability at high current density in neutral conditions. NiFe hydroxide electrode obtains an outstanding performance of 1000mA cm-2 at low overpotential of 218mV with 1000 h operation at 100mA cm-2. Electrochemical experiments and theoretical calculations have demonstrated that the interfacial fluoride contributes to promote the adsorption of Pt to proton for sustaining a large current density at low potential, while the Pt single atoms/nanoparticles provide H adsorption sites. The synergy effect of F and Pt species promotes the formation of Pt─H and F─H bonds, which accelerate the adsorption and dissociation process of H2O and promote the HER reaction with a long-term durability in neutral conditions.

Sulfur-Bridged Asymmetric CuNi Bimetallic Atom Sites for CO2 Reduction with High Efficiency.

Double-atom catalysts (DACs) with asymmetric coordination are crucial for enhancing the benefits of electrochemical carbon dioxide reduction and advancing sustainable development, however, the rational design of DACs is still challenging. Herein, this work synthesizes atomically dispersed catalysts with novel sulfur-bridged Cu-S-Ni sites (named Cu-S-Ni/SNC), utilizing biomass wool keratin as precursor. The plentiful disulfide bonds in wool keratin overcome the limitations of traditional gas-phase S ligand etching process and enable the one-step formation of S-bridged sites. X-ray absorption spectroscopy (XAS) confirms the existence of bimetallic sites with N2Cu-S-NiN2 moiety. In H-cell, Cu-S-Ni/SNC shows high CO Faraday efficiency of 98.1% at -0.65V versus RHE. Benefiting from the charge tuning effect between the metal site and bridged sulfur atoms, a large current density of 550mAcm-2 can be achieved at -1.00V in flow cell. Additionally, in situ XAS, attenuated total reflection surface-enhanced infrared absorption spectroscopy (ATR-SEIRAS), and density functional theory (DFT) calculations show Cu as the main adsorption site is dual-regulated by Ni and S atoms, which enhances CO2 activation and accelerates the formation of *COOH intermediates. This kind of asymmetric bimetallic atom catalysts may open new pathways for precision preparation and performance regulation of atomic materials toward energy applications.

Six year efficacy of silvicultural treatments to control American beech regeneration in stands affected by beech bark disease in Ontario, Canada

High beech regeneration density is a concern in northern shade tolerant hardwood forests. High densities of beech ( Fagus grandifolia Ehrh) regeneration can crowd out other desirable species, such as sugar maple ( Acer saccharum Marsh.), and jeopardize long-term sustainability since beech is under threat from beech bark disease ( Cryptococcus fagisuga/Neonectria spp. Complex). We examined the efficacy of three tending (no tending, brush saw, and basal bark herbicide) and two timing and harvesting (deferred 5 years post-single tree selection harvest, concurrent with uniform shelterwood harvest) treatments on reducing beech regeneration density and promoting sugar maple regeneration density over 6 years. Six years after tending, we found that large beech regeneration density was reduced, medium beech regeneration density had recovered to pre-tending levels in most treatments, and small beech regeneration density remained unaffected. Tending treatments had no effect on any size class of sugar maple regeneration density but the uniform shelterwood harvest promoted medium sugar maple density more than the single-tree selection harvest. Despite this increase, in all treatment combinations sugar maple regeneration densities remained below stocking targets. Our results suggest that while tending treatments can temporarily reduce beech regeneration densities, sugar maple is unable to take advantage of the increased growing space.

Cation vacancy modulated Cu3P-CoP heterostructure electrocatalyst for boosting hydrogen evolution at high current densities and coupling Zn-H2O battery

Exploiting highly efficient, cost-effective and stable electrocatalysts is key to decreasing hydrogen evolution reaction (HER) kinetics energy barrier. Herein, the alkaline HER kinetics energy barrier can greatly reduce by the joint strategies of the cation vacancy and heterostructure engineering, which is seldom explored and remains ambiguous. In this study, an efficient and stable copper foam-supported Cu3P-CoP heterostructure electrocatalyst with cation vacancy defects (defined as Cu3P-CoP-VAl/CF) was designed for HER via the successive coprecipitation, electrodeposition, alkali etching and phosphorization treatments. As anticipated, the as-obtained Cu3P-CoP-VAl/CF electrocatalyst reveals a remarkable catalytic activity for HER with a low overpotential of 205 mV at a current density of 100 mA·cm−2, a high turnover frequency value of 1.05 s−1 at an overpotential of 200 mV and a small apparent activation energy (Ea) of 9 kJ·mol−1, while shows superior long-term stability at large current densities of 100 and 240 mA·cm−2. Systematic experiment and characterization data demonstrate that the formed cation vacancy could optimize the Ea, leading to the decrease of the kinetic barriers of Cu3P-CoP/CF heterostructure, as well as the established heterogeneous interface induced a synergistic effect between biphasic components on boosting the kinetics toward HER. The results of density functional theory disclose that the synergistic effect of Cu3P-CoP heterostructure could decrease the energy barrier and optimize Gibbs free energy of hydrogen adsorption, resulting in the enhancement of intrinsic catalytic activity of Cu3P-CoP-VAl/CF. More significantly, the alkali-cell assembled by Cu3P-CoP-VAl/CF (cathode) and RuO2/CF (anode) behaves outstanding water splitting performance, delivering a current density of 10 mA·cm−2 at a relatively small applied voltage of 1.58 V, along with encouraging long-term durability. In addition, the alkaline Zn-H2O battery with Cu3P-CoP-VAl/CF as the cathode has been fabricated for the simultaneous generation of electricity and hydrogen, which displays a large power density of up to 4.1 mW·cm−2. The work demonstrates that rational strategy for the design of competent electrocatalysts can effectively accelerate the kinetics of HER, which supplies valuable insights for practical applications in overall water splitting.

Transient characterization of the mode switching process in the reversible solid oxide cell stack

Reversible solid oxide cells (RSOCs) is a promising energy storage and conversion technology requiring frequent switching between fuel cell mode and electrolysis mode in practice. Unfortunately, it may cause a large current density undershoot that has irreversible damage to the RSOC. Therefore, understanding the transient behaviors of the RSOC is critical for its efficient and durable operation. A three-dimensional transient model of a 30-cell SOC stack with an external manifold is established. From SOFC to SOEC, the mass transfer lag and slow heat transfer cause the current density of the stack requiring 2500 s to reach a steady state. And the bottom inlet way and the external manifold structure cause differences in the current density, molar fraction and temperature variation with time between different cells. The upper cells show a slower mass transfer rate and undergo greater temperature changes. The inconsistent temperature change gradients and temperature change rates among different cells will inevitably produce changing thermal stresses and bring irreversible mechanical losses to the stack. Similar transient characteristics are observed when switching from SOEC to SOFC. However, it takes longer time (3200 s) to achieve the final steady state.

Amorphous/crystalline NiFe LDH hierarchical nanostructure for large-current-density electrocatalytic water oxidation

Amorphous structure shows more catalytic active sites but poor conductivity towards oxygen evolution reaction (OER). Herein, we fabricated a novel three-dimensional (3D) self-supported NiFe layered double hydroxides (LDH) catalytic material with amorphous/ crystalline interface, aiming to obtain both excellent catalytic activity and conductivity. This homogeneous hierarchical structure exhibits a high catalytic activity and robustness, giving the industrially required current density of 1000 mA cm−2 at an ultralow overpotential of 359.8 mV with 240-hour stability in 1 M KOH. In-situ electrochemical tests reveal that the amorphous/crystalline interface boosts the intermediates evolution and OER kinetics, which might be ascribed to considerable active sites and fast charge transfer. Moreover, the 3D structure has unique superhydrophilicity and superaerophobicity, which can further accelerate the electrolyte penetration, facilitate the bubbles desorption from the electrode, enhance mass transport, and thus improve OER performance at large current densities. This work provides a feasible way to develop high-performance electrocatalytic material via constructing homogeneous amorphous/crystalline interface.

Achieving High-Performance Na3V2(PO4)2F3 Cathode Material through a Bifunctional N-Doped Carbon Network.

Na3V2(PO4)2F3 (NVPF) is emerging as a popular cathode for sodium-ion batteries owing to its stable structure, high operating voltage, and large energy density. However, its practical application is hindered by its low conductivity. In addition, due to the loss of fluorine during synthesis, Na3V2(PO4)3 (NVP) impurity is often easily generated, resulting in a decrease in actual operating voltage. Herein, a bifunctional carbon network composed of an N-doped carbon layer and carbon bridge is constructed around NVPF particles. Through pyrolysis of polydopamine (PDA), the NVPF particles are covered in situ by an N-doped carbon layer, and the carbon bridge generated by polytetrafluoroethylene (PTFE) is also coated with N-doped carbon. Besides, PTFE also serves as a fluorine supplement to ensure that pure NVPF is obtained. As a result, the bifunctional N-doped carbon network-modified NVPF delivers a high reversible capacity (125.7 mA h g-1 at 0.2 C) and appreciable cycle stability (92.7% at 1 C over 300 cycles, and 89.8% at 10 C over 1500 cycles). When assembled into a full cell with a commercial hard carbon anode, it displays a discharge median voltage of up to 3.62 V at 0.2 C. Furthermore, it achieves a high energy density of 373.7 W h kg-1 at a power density of 461.2 W kg-1, with an excellent specific energy retention of 78.2% after 200 cycles. Therefore, this modification method is expected to be extended to other fluorine-containing materials with poor electrical conductivity.

Nonprecious and shape-controlled Co3O4-CoO@Co electrocatalysts with defect-rich and spin-state altering properties to accelerate hydrogen evolution reaction at large current densities over a wide pH range

In this study, efficient HER activity is achieved through the successful preparation of Co3O4-CoO@Co catalysts that are morphology-dependent. It is proposed that the distinctive skeletal polyhedron (SPH) morphology of the Co3O4-CoO@Co catalyst shows outstanding HER performances over the universal pH range. The heterostructure catalyst exhibits a current density of 50 mAcm−2 at an ultra-low overpotential of 28, 62, and 138 mV under 0.5 M H2SO4, 1 M KOH, and 1 M PBS electrolytes, respectively. Experimental and theoretical studies indicate that electron-enriched Co2+ in the CoO site is favorable for H+ cation adsorption and high valence Co3+ in the Co3O4 site is favorable for H2O molecule activation and dissociation in acidic, neutral, and alkaline electrolytes. Benefitting from an empty eg 3d orbital with a strong Jahn–Teller effect, a high density of spin states, and a large number of oxygen vacancies, the SPH-Co3O4-CoO@Co catalyst is demonstrated to provide faster hydrogen evolution reaction.

High-capacity K+-pillared layered manganese dioxide as cathode material for high-rate aqueous zinc-ion battery

Sluggish kinetics and severe structural instability of manganese-based cathode materials for rechargeable aqueous zinc-ion batteries (ZIBs) lead to low-rate capacity and poor cyclability, which hinder their practical applications. Pillaring manganese dioxide (MnO2) by pre-intercalation is an effective strategy to solve the above problems. However, increasing the pre-intercalation content to realize stable cycling of high capacity at large current densities is still challenging. Here, high-rate aqueous Zn2+ storage is realized by a high-capacity K+-pillared multi-nanochannel MnO2 cathode with 1 K per 4 Mn (δ-K0.25MnO2). The high content of the K+ pillar, in conjunction with the three-dimensional confinement effect and size effect, promotes the stability and electron transport of multi-nanochannel layered MnO2 in the ion insertion/removal process during cycling, accelerating and accommodating more Zn2+ diffusion. Multi-perspective in/ex-situ characterizations conclude that the energy storage mechanism is the Zn2+/H+ ions co-intercalating and phase transformation process. More specifically, the δ-K0.25MnO2 nanospheres cathode delivers an ultrahigh reversible capacity of 297 mAh g−1 at 1 A g−1 for 500 cycles, showing over 96 % utilization of the theoretical capacity of δ-MnO2. Even at 3 A g−1, it also delivered a 63 % utilization and 64 % capacity retention after 1000 cycles. This study introduces a highly efficient cathode material based on manganese oxide and a comprehensive analysis of its structural dynamics. These findings have the potential to improve energy storage capabilities in ZIBs significantly.

Modulating the Energy Barrier via the Synergism of Cu3P and CoP to Accelerate Kinetics for Bolstering Oxygen Electrocatalysis in Zn-Air Batteries.

Modulating the energy barrier of reaction intermediates to surmount sluggish kinetics is an utterly intriguing strategy for amplifying the oxygen reduction reaction. Herein, a Cu3P/CoP hybrid is incorporated on hollow porous N-doped carbon nanospheres via dopamine self-polymerization and high-temperature treatment. The resultant Cu3P/CoP@NC showcases a favorable mass activity of 4.41 mA mg-1 and a kinetic current density of 2.38 mA cm-2. Strikingly, the catalyst endows the aqueous Zn-air battery (ZAB) with a large power density of 209.0 mW cm-2, superb cyclability over 317 h, and promising application prospects in flexible ZAB. Theoretical simulations reveal that Cu functions as a modulator to modify the free energy of intermediates and adsorbs the O2 on the Co sites, hence rushing the reaction kinetics. The open and hydrophilic hollow spherical mesoporous structure provides unimpeded channels for reactant diffusion and electrolyte penetration, whereas the exposed inner and outer surfaces can confer a plethora of accessible actives sites. This research establishes a feasible design concept to tune catalytic activity for non-noble metal materials by construction of a rational nanoframework.

New analysis of the temperature-dependent threshold density for electron self-trapping in gaseous helium.

We present the results of a new analysis of the literature data on electron mobility μ in dense helium gas aimed at determining the existence of a threshold density for electron self-trapping in gaseous helium as a function of temperature. We have investigated the density dependence of μ and, when available, its dependence on the electric field. The experimental data are favorably rationalized by minimizing the excess free energy of the self-localized states within the optimum fluctuation model. It is shown that the formation of electron bubbles via the self-trapping phenomenon is determined by the delicate balance between the electron thermal energy, the density dependence of the electron energy at the bottom of the conduction band in the gas, and the work necessary to expand the bubble. We show that the self-trapping phenomenon is not limited to low temperatures but occurs at any temperatures for large enough densities.

Performance-enhanced tribovoltaic nanogenerator by regulating carrier transportation with an asymmetric heterostructure

The tribovoltaic nanogenerator (TVNG) is emerging as a promising circuit-integrative energy harvester, with notable advantages like direct current output and large current density. Nevertheless, the research on optimizing charge excitation and carrier transportation remains deficient. In this work, we report an alternative approach for practically promoting the output performance of silicon (Si)-based TVNG. A well-designed asymmetric heterostructure is achieved by inserting an appropriate interlayer between the friction layer and the bottom electrode. Carrier extraction efficiency has been promoted effectively, while carrier recombination has been restrained owing to the built-in electric field excited by p-Si/ZnO heterojunction. The coupling mechanism of the built-in electric field and the interfacial electric field has been revealed explicitly with a comprehensive theoretical model, which is based on the capacitance feature of the PN junction. The designed multilayer TVNG (MTVNG) has shown 20 times higher output compared to normal Si-based TVNGs. Apart from presenting fundamental insights into the tribovoltaic effect, we have developed a dual-mode analysis method for vibration monitoring. This work expands the path to improve TVNG output through multi-electric field coupling and provides new inspiration for miniaturized vibration sensors in real-time deployments.

Evolution of the network structure and voltage loss of anode electrode with the polymeric dispersion in PEM water electrolyzer

Exploring the intrinsic relationship between the network structure and the performance of catalyst layer (CL) by rational design its structure is of paramount importance for proton exchange membrane (PEM) electrolyzers. This study reveals the relative effect of polymeric dispersion evolution on oxygen evolution reaction (OER) performance and cell voltage loss and linked to CL network structure. The results show that although the dispersed particle size of the ionomer and ink increases with increasing the solubility parameter (δ) difference between the mixed solvent and the ionomer, MeOH-cat (ink from MeOH aqueous solution) has the largest ionomer and ink particle size resulting in the poorest stability, but has comparable OER overpotential to that of IPA-cat (249 mV@10 mA cm−2), which has the smallest dispersed size. While at 100 mA cm−2, the overpotential of the ink rises as the particle size increases, suggesting that the electrode structure becomes more influential as the current density increases. Quantitatively analyzed the electrolyzers’ voltage losses and determined that the CL from MeOH-cat has the lowest kinetic overpotential. However, its performance is the worst because of the insufficient network structure of CL, resulting in an output of 1.96 V at 1.5 A cm−2. Comparatively, the CL from IPA-cat has the highest kinetic overpotential yet can achieve the greatest performance of 1.76 V at 2 A cm−2 due to its homogeneous network structure and optimal mass transport. Furthermore, the performance variation becomes more pronounced as current density rises. Hence, this study highlights the significant impact of CL structure on electrolyzer’s performance. To improve performance in PEM water electrolysis technology, especially for large work current density, it is crucial to enhance the CL’s network structure.

Coexistence of near- EF Flat Band and Van Hove Singularity in a Two-Phase Superconductor

Quantum many-body systems, particularly, the ones with large near-EF density states, are well known for exhibiting rich phase diagrams as a result of enhanced electron correlations. The recently discovered locally noncentrosymmetric heavy fermion superconductor CeRh2As2 has stimulated extensive attention due to its unusual H−T phase diagram consisting of two-phase superconductivity, antiferromagnetic order, and possible quadrupole-density wave orders. However, the critical near-EF electronic structure remains experimentally elusive. Here, we provide this key information by combining soft-x-ray and vacuum ultraviolet (VUV) angle-resolved-photoemission-spectroscopy measurements and atom-resolved density-functional-theory (DFT)+U calculations. With bulk-sensitive soft x ray, we reveal quasi-2D hole and electron pockets near the EF. On the other hand, under VUV light, the Ce flat bands are resolved with the c−f hybridization persisting up to well above the Kondo temperature. Most importantly, we observe a symmetry-protected fourfold Van Hove singularity (VHS) coexisting with the Ce 4f5/21 flat bands at the X point, which, to the best of our knowledge, has never been reported before. Such a rare coexistence is expected to lead to a large density of states at the zone edge, a large upper critical field of the odd-parity phase, as well as spin and/or charge instabilities with a vector of (1/2, 1/2, 0). Uniquely, it will also result in a new type of f-VHS hybridization that alters the order and fine electronic structure of the VHS and flat bands. Our findings provide not only key insights into the nature of multiple phases in CeRh2As2 but also open up new prospects for exploring the novelties of many-body systems with f-VHS hybridization. Published by the American Physical Society 2024

Predicted hot superconductivity in LaSc2H24 under pressure

The recent theory-driven discovery of a class of clathrate hydrides (e.g., CaH6, YH6, YH9, and LaH10) with superconducting critical temperatures (Tc) well above 200 K has opened the prospects for "hot" superconductivity above room temperature under pressure. Recent efforts focus on the search for superconductors among ternary hydrides that accommodate more diverse material types and configurations compared to binary hydrides. Through extensive computational searches, we report the prediction of a unique class of thermodynamically stable clathrate hydrides structures consisting of two previously unreported H24 and H30 hydrogen clathrate cages at megabar pressures. Among these phases, LaSc2H24 shows potential hot superconductivity at the thermodynamically stable pressure range of 167 to 300 GPa, with calculated Tcs up to 331 K at 250 GPa and 316 K at 167 GPa when the important effects of anharmonicity are included. The very high critical temperatures are attributed to an unusually large hydrogen-derived density of states at the Fermi level arising from the newly reported peculiar H30 as well as H24 cages in the structure. Our predicted introduction of Sc in the La-H system is expected to facilitate future design and realization of hot superconductors in ternary clathrate superhydrides.