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High-pressure heaters in large volume presses must reconcile potentially contradictory properties, and the whole high-pressure and high-temperature (HPHT) community has been engaged for years to seek a better heater. LaCrO

As an unusual mechanical response, the ferroelastic phenomenon in two-dimensional materials has been reported both experimentally and theoretically in recent years. Here, we present the theoretical findings of ferroelastic switching in monolayer PdS2. We demonstrate four types of PdS2 allotropes, showing excellent ferroelasticity with low ferroelastic barriers and strong switching signals. The ferroelastic transitions in monolayer PdS2 include the lattice rotation in penta-α PdS2, the transformation between penta-α PdS2 and penta-β PdS2, the transformation between penta-α PdS2 and penta-γ PdS2, the transformation between penta-β PdS2 and penta-γ PdS2, the transformation between penta-α PdS2 and δ PdS2, and the lattice rotation in δ PdS2. The ferroelastic transitions between these four allotropes have revealed the flexible ferroelasticity in monolayer PdS2. Specifically, the flexible switching in PdS2 allotropes may efficiently control the anisotropic transport of electrons. Thus, the presence of these outstanding mechanical properties endows PdS2 with great potential for applications in next-generation shape memory devices.

In this article, we design a MIM waveguide-coupled resonator system. This resonant cavity has a semicircular ring cavity with the square cavity (SRSC). The effect of that Fano phenomenon on this sensing property on this system is explained in detail by using the finite different time domain method and finite element analysis method. This sensor was analyzed by COMSOL Multiphysics 5.4a simulation software to explore the influences of the structural arguments to the sensitivity. After structure optimization, a sensitivity of the sensor can reach 1640 nm/RIU, and the figure of merit (FOM) of this system is 41. This has great application prospects in the field of integrated optical circuits and biosensing.

Understanding the electric dipole switching in multiferroic materials requires deep insight of the atomic-scale local structure evolution to reveal the ferroelectric mechanism, which remains unclear and lacks a solid experimental indicator in high-pressure prepared LiNbO3-type polar magnets. Here, we report the discovery of Zn-ion splitting in LiNbO3-type Zn2FeNbO6 established by multiple diffraction techniques. The coexistence of a high-temperature paraelectric-like phase in the polar Zn2FeNbO6 lattice motivated us to revisit other high-pressure prepared LiNbO3-type A2BB'O6 compounds. The A-site atomic splitting (∼1.0-1.2 A between the split-atom pair) in B/B'-mixed Zn2FeTaO6 and O/N-mixed ZnTaO2N is verified by both powder X-ray diffraction structural refinements and high angle annular dark field scanning transmission electron microscopy images, but is absent in single-B-site ZnSnO3. Theoretical calculations are in good agreement with experimental results and suggest that this kind of A-site splitting also exists in the B-site mixed Mn-analogues, Mn2FeMO6 (M = Nb, Ta) and anion-mixed MnTaO2N, where the smaller A-site splitting (∼0.2 A atomic displacement) is attributed to magnetic interactions and bonding between A and B cations. These findings reveal universal A-site splitting in LiNbO3-type structures with mixed multivalent B/B', or anionic sites, and the splitting-atomic displacement can be strongly suppressed by magnetic interactions and/or hybridization of valence bands between d electrons of the A- and B-site cations.

LiNbO3 (LN)-type polar magnets are technologically important but require stringent and costly high-pressure synthesis with very limited sample yields. We develop a chemical strategy to reduce the physical synthesis pressure. LN-type polar magnets require 7 GPa to stabilize in the high-pressure Mn2FeNbO6 (MFNO) phase. Here, MFNO was successfully stabilized in the isostructural LN matrix at intermediate physical pressure (below 5 GPa) at gram levels for each run by dilution with LN according to (Li1–xMnx)(Fex/2Nb1–x/2)O3 (x = 0.18, 0.33, 0.46, 0.57). LN-diluted MFNO demonstrates ferromagnetism above room-temperature (magnetic ordering temperature TC ≈ 516–554 K) and has large estimated spontaneous polarization (PS ≈ 18–63 μC/cm2). Irreversible c-axis near-zero thermal expansion stemming from magnetostriction was observed around the magnetic transition temperature region upon heating at ambient pressure, which irreversibly elongates the distance between the face-sharing (Li/Mn) and (Fe/Nb) octahedral centroi...

Exotic perovskites significantly enrich materials for multiferroic and magnetoelectric applications. However, their design and synthesis is a challenge due to the mostly required recipe conditions at extremely high pressure. Herein, we presented the Ca2−xMnxMnTaO6 (0 ≤ x ≤ 1.0) solid solutions stabilized by chemical pressure assisted with intermediate physical pressure up to 7 GPa. The incorporation of Mn2+ into the A-site neither drives any cationic ordering nor modifies the orthorhombic Pbnm structure, namely written as (Ca1−x/2Mnx/2)(Mn1/2Ta1/2)O3 with disordered A and B site cationic arrangements. The increment of x is accompanied by a ferromagnetic to antiferromagnetic transition around x = 0.2, which is attributed to the double-exchange interactions between A-site Mn2+ and B-site Mn3+. Partial charge disproportionation of the B-site Mn3+ into Mn2+ and Mn4+ occurs for x above 0.8 samples as manifested by X-ray spectrum and magnetic behaviors. The coexistence of B-site Mn3+ (Jahn–Teller distortion ion) and B′-site Ta5+ (second-order Jahn–Teller distortion ion) could be energetically responsible for the absence of A-site columnar ordering as observed in other quadruple perovskites with half of the A-sites occupied by small transition-metal cations. These exceptional findings indicate that exotic perovskites can be successfully stabilized at chemical and intermediate physical pressure, and the presence of Jahn–Teller distortion cations at the same lattice should be avoided to enable cationic ordering.

The rational design of multifunctional inorganic pigments relies on the manipulation of ionic valence and local surroundings of a chromophore in structurally and chemically habitable hosts. To date, the development of environmentally benign and intense violet/purple pigments is still a challenge. Here we report a family of A3-xMnxTeO6 and A3-2xMnxLixTeO6 (A = Zn, Mg; x = 0.01-0.15) pigments colored by site-selective Mn2+O4 yellow and Mn3+O5-6 violet chromophores. Zn2.9Mn0.1TeO6 is intense bright yellow, comparable with commercial BiVO4, and has better near-infrared reflectivity (∼89%) in comparison to commercial TiO2. The codoped Li+ "activator" generates holes and charge-balanced Mn3+ (Mn3+O5-6), realizing a color transformation from yellow to the bright violet pigments of A3-2xMnxLixTeO6. The most vivid Mg2.8Mn0.1Li0.1TeO6 is probably the best violet pigment known to date, exhibits excellent chemical and thermodynamic stability, and demonstrates pressure-dependent stability up to 5-7 GPa, before a (reversible) phase transition to pink. Theoretical calculations revealed the correlation between site-preference occupancy and chromophore motifs and predicted a wide color gamut of pigments in Zn3TeO6-hosted 3d transition-metal ions other than manganese.

As an unusual mechanical response, the ferroelastic phenomenon in two-dimensional materials has been reported both experimentally and theoretically in recent years. Here, we present the theoretical findings of ferroelastic switching in monolayer PdS2. We demonstrate four types of PdS2 allotropes, showing excellent ferroelasticity with low ferroelastic barriers and strong switching signals. The ferroelastic transitions in monolayer PdS2 include the lattice rotation in penta-α PdS2, the transformation between penta-α PdS2 and penta-β PdS2, the transformation between penta-α PdS2 and penta-γ PdS2, the transformation between penta-β PdS2 and penta-γ PdS2, the transformation between penta-α PdS2 and δ PdS2, and the lattice rotation in δ PdS2. The ferroelastic transitions between these four allotropes have revealed the flexible ferroelasticity in monolayer PdS2. Specifically, the flexible switching in PdS2 allotropes may efficiently control the anisotropic transport of electrons. Thus, the presence of these outstanding mechanical properties endows PdS2 with great potential for applications in next-generation shape memory devices.

With the development of the economy, the continuation of the energy crisis and the environmental pollution, the development and utilization of new energy sources become particularly important, especially solar energy, but the current heat collection efficiency of solar collectors cannot meet the requirements. In this paper, a Novel Phase Change Thermal Storage Solar Collector (PCMSC) was designed. The air was used as the heat exchange medium. The Spiral Double-pass Direct-current (SDDC) Structure was applied to the vacuum tube of air-type solar energy collector. An energy storage core was provided inside the heat collecting tube, and the inside of the energy storage core was filled with Composite phase-change heat-storage material (PCHM). Due to the addition of the energy storage core, the energy storage core occupies most of the space of the vacuum tube, which narrows the flow channel in the vacuum tube, which has a certain impact on the internal flow field of the collector. The influence of the energy storage core on the air flow inside the collector tube was analyzed. The results show that the increase of the energy storage core increases the airflow speed in the vacuum tube, and also improves the airflow uniformity inside the collector.

Molybdenum sulfide (MoS2) has attracted great interest as a promising non-precious-metal catalyst candidate to replace the precious-metal Pt catalysts for the hydrogen evolution reaction (HER). Nevertheless, the catalytic efficiency of MoS2 is significantly restricted by its density of catalytic active sites and inert basal plane. In this work, we have designed a facile one-pot solvothermal method to synthesize porous 1T-MoS2 that is integrated with atomic doping of Cu atoms. The as-prepared Cu@MoS2 sample exhibits enhanced HER performance with a low overpotential of 131 mV at the current density of 10 mA/cm2, a small Tafel slope of 51 mV/dec and as well as a good long-term stability. Enhanced HER performance can be ascribed to the synergistic effect of 1T-MoS2 metallic phase, single atom Cu doping and numerous sulfur vacancies. Theoretical calculations indicates that the adsorption energy of Cu atom on 1T-MoS2 surface (−3.68 eV) is much higher than that on 2H-MoS2 surface (−1.94 eV), moreover, the Cu atom adsorbed on the surface of the 1T-MoS2 has larger charge transfer (−0.38e), which can be contributed to further enhance HER performance of 1T-MoS2.

Exploring a simple model system to realize the intrinsic guidelines of activity for oxide electrocatalysts is urgent and important. Here, we introduce delafossite oxides A 2IrO3 (A = Li, Na, Cu) as a family of oxygen evolution reaction electrocatalysts in alkaline media. We show that, in Cu2IrO3, the intrinsic intersite charge transfer between Cu and Ir improves the electrocatalytic activity by simultaneously increasing the conductivity and reducing the Tafel slope down to 51 mV dec−1 with an overpotential η 10 = 361 mV. Through a comparative study, the improved activity of Cu2IrO3 is attributed to the increase of Ir 5d projected electronic density of states with extended Ir–O bond length. This study provides insights into advanced catalyst design through tailoring the active site of oxides by the modulation of electronic states in a given structural motif.

Understanding the electric dipole switching in multiferroic materials requires deep insight of the atomic-scale local structure evolution to reveal the ferroelectric mechanism, which remains unclear and lacks a solid experimental indicator in high-pressure prepared LiNbO

Rational design of technologically important exotic perovskites is hampered by the insufficient geometrical descriptors and costly and extremely high-pressure synthesis, while the big-data driven compositional identification and precise prediction entangles full understanding of the possible polymorphs and complicated multidimensional calculations of the chemical and thermodynamic parameter space. Here we present a rapid systematic data-mining-driven approach to design exotic perovskites in a high-throughput and discovery speed of the A(2)BB'O-6 family as exemplified in A(3)TeO(6). The magnetoelectric polar magnet Co3TeO6, which is theoretically recognized and experimentally realized at 5 GPa from the six possible polymorphs, undergoes two magnetic transitions at 24 and 58 K and exhibits helical spin structure accompanied by magnetoelastic and magnetoelectric coupling. We expect the applied approach will accelerate the systematic and rapid discovery of new exotic perovskites in a high-throughput manner and can be extended to arbitrary applications in other families., National Science Foundation of ChinaNational Natural Science Foundation of China (NSFC) [NSFC-21875287, 21801253, 11804404]; Program for Guangdong Introducing Innovative and Entrepreneurial Teams [2017ZT07C069]; Institutional Strategy of the University of Cologne within the German Excellence Initiative; Deutsche Forschungsgemeinschaft (DFG, German Research Foundation)German Research Foundation (DFG) [277146847 -SFB 1238]; DOEBESUnited States Department of Energy (DOE) [DE-SC0012704], We gratefully acknowledge the discussion of the piezoresponse behavior with Professor X. S. Gao at South China Normal University. This work was financially supported by the National Science Foundation of China (NSFC-21875287, 21801253, and 11804404), the Program for Guangdong Introducing Innovative and Entrepreneurial Teams (2017ZT07C069), and The Institutional Strategy of the University of Cologne within the German Excellence Initiative and the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) - Projektnummer 277146847 -SFB 1238 (B02). The XANES work at the Brookhaven National Laboratory, NSLS-II was supported by the DOEBES (DE-SC0012704).

Amorphous MoO3-x with enhanced LSPR has been fabricated successfully by introducing Mo atoms into the interlayers of MoO3 nanosheets via a hydrothermal method. The inserted Mo atom could bond with inherent Mo atoms and further form a distorted atomic configuration structure. Thus, the amorphous MoO3-x possesses a relatively excellent photothermal conversion efficiency of 61.79%.

A prototypical family of Ruddlesden−Popper (R-P) iridate oxides Srn+1IrnO3n+1 (n = 1, 2, and ∞) was investigated to intensify systematic understanding of the intrinsic activity of the bulk crystal structure on oxygen evolution reaction (OER). Compared with IrO2, these oxides contain less iridium and show higher catalytic activity. Especially, Sr3Ir2O7 (n = 2) displays enhanced activity of the optimum that is programmed by the dimensionality of the bulk crystal structure. As n decreased, a distinct d-band center downshift leads to weakened adsorption of oxygen intermediates, which accelerates the kinetics. Calculations also reveal an elevated conductivity in overall values from n = 1, 2 to ∞. Both the increased conductivity and optimized binding energy contribute the exceptional OER activity of Sr3Ir2O7. This work suggests a significant advance in understanding the relationship between intrinsic activity and the bulk crystal structure of R-P oxides.

Combining the peculiar properties of different ingredients in one ultimate material is an efficient route to achieve the desired functional materials. Compared to 2H-MoS 2 , 1T-MoS 2 nanosheets display the perfect performance of hydrogen evolution reaction (HER) because of the excellent electronic conductivity. However, how to further realize HER in the visual and near-infrared (NIR) region is a great challenge. Herein, we develop an efficient method to locally pattern h-MoO 3 on the ultrathin metallic 1T-MoS 2 nanosheets and obtain the novel heterostructures of h-MoO 3 /1T-MoS 2 . The enhanced photoelectrochemical performance of the as-prepared heterostructures has been demonstrated. Our study indicates it is originated from the synergistic effect between h-MoO 3 and 1T-MoS 2 , i.e., the strong optical absorption of h-MoO 3 in the visible and NIR region, the excellent electronic conductivity of 1T-MoS 2 and as well as the efficient separation of the photo-induced carriers from the heterostructures.

Based on an evacuated tube collector, we designed an air–type double–pass solar collector with a PCM–rod embedded in a vacuum tube. In this study, the basic parameters of the proposed collector are discussed comprehensively and the spatial layout of each component is illustrated. Simultaneously, a thermal model of the collector has been established to predict the outlet temperature of the collector. The equivalent thermal efficiency of the phase change material is also proposed to explain the change in the thermal efficiency of the collector caused by the PCM. Finally, the thermal performance of the proposed collector was tested and compared with its theoretical value. The results show that the comparison between the simulated and experimentally measured outlet temperatures is in good agreement; the root mean square error and mean bias difference on the outlet temperature are 1.56 K and 1.33 K, respectively. Additionally, even if the irradiation intensity reduces by 39% within 30 min, the outlet temperature decreases by only 7.5 K. The thermal model is also used to analyze the influence of airflow, radiation intensity, ambient temperature and surrounding air speed on the outlet temperature. It was observed that the first three have a greater impact, but the temperature fluctuation is only 0.36% when ambient wind speed is 0.2–2 m/s. In contrast, the heat loss of the collector was evaluated and it was found that the heat loss of the vacuum tube accounted for 0.4%–2.8% of the heat energy of the collector, while the heat loss of the manifold to the ambient accounted for only 0.04%. The phase change material stored 0.247 MJ of heat, of which 0.245 MJ was provided to air, and the conversion rate of heat absorption and release was 99.2%, and the working time of the collector is extended by 8 h. In terms of thermal efficiency, the instantaneous thermal efficiency continued to increase from 13% to 397%, and the equivalent thermal efficiency of the phase change material reached a maximum of 484%.

As a remarkable class of plasmonic materials, two dimensional (2D) semiconductor compounds have attracted attention owing to their controlled manipulation of plasmon resonances in the visible light spectrum, which outperforms conventional noble metals. However, tuning of plasmonic resonances for 2D semiconductors remains challenging. Herein, we design a novel method to obtain amorphous molybdenum oxide (MoO3 ) nanosheets, in which it combines the oxidation of MoS2 and subsequent supercritical CO2 -treatment, which is a crucial step for the achievement of amorphous structure of MoO3 . Upon illumination, hydrogen-doped MoO3 exhibits tuned surface plasmon resonances in the visible and near-IR regions. Moreover, a unique behavior of the amorphous MoO3 nanosheets has been found in an optical biosensing system; there is an optimum plasmon resonance after incubation with different BSA concentrations, suggesting a tunable plasmonic device in the near future.

With increase in global temperature, worsening of environmental conditions and a shortage of energy resources, countries around the world are actively developing the use of renewable energy sources. The technology of combining solar energy and heat pumps is an important direction for the development of new energy utilization technologies. In this paper, a solar phase change heat storage evaporative heat pump system (SPHP) is designed. The system uses a phase change heat storage tank as the connection center, and is coupled with a solar system and a heat pump system. The phase change heat storage tank is filled with ammonium aluminum sulfate dodecahydrate /stearic acid composite phase change heat storage material. The system was experimentally studied, and the analysis of a system simulation was performed using TRNSYS. The results show that the heating electricity consumption of the system is about 72.8% of that of a single heat pump, the daily operating cost is only 41.2% of that for a single heat pump heating system, the average system coefficient of performance (COP) reaches 3.79, the average heat collection efficiency of the solar collector can reach 59.8%, and the system solar energy proportion of heat supply is 27.2%. There was good agreement between the experimental and simulation results for the system COP and temperature of the heating end equipment.