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Conversion-reaction induced charge storage mechanisms of transition metal sulphides have received considerable interest in designing high-capacity electrodes for electrochemical energy storage devices. However, their low conductivity and structural degradation during cycling limit their applications as energy storage devices. A combination of different nickel sulphide phases tailored with carbon nanostructures is suggested to address these limitations. Herein, a facile, two-step approach is demonstrated for fabricating a hybrid electrode, consisting of trinickel disulphide (Ni3S2) formed on a metallic Ni nanoparticle supported by vertical carbon nanotubes (VCN) backbone in the form Ni3S2/Ni@VCN. Ni3S2/Ni@VCN electrodes were tested as anode for lithium-ion batteries, and the electrode featured outstanding lithium-storage capabilities with a high reversible capacity (1113 mAh g−1 after 100 cycles at 100 mA g−1), excellent long-term cycling stability (770 mAh g−1 after 500 cycles at 200 mA g−1), and good rate capability. The resulting electrode performance is one of the best Li-ion storage capabilities in the Ni3S2-type anode materials described. A unique “broccoli-like” structure of polycrystalline Ni3S2 capped on conductive VCN backbone helps the interface storage process and boosts lithium storage performance.

Although structural stability, non-toxicity, and low cost have attracted industrial attention, Li2ZnTi3O8 (LZTO) is difficult to utilize as an anode material for LIB due to its poor ionic and electronic conductivity. In this research, forming a composite with TiO2 and coating nitrogen-doped carbon on the composite have been carried out to enhance the performance of LZTO. Since the 100 cycles at 200 mA g-1, the nitrogen-doped carbon coated LZTO/TiO2 composite anode material exhibits 80% higher specific discharge capacity than specific discharge capacity of bare LZTO. Furthermore, excellent rate capability and increased specific discharge capacity at high current density are achieved, thus demonstrating the improvements on the electrochemical performance of LZTO stemming from the synergistic effects of composite formation with TiO2 and nitrogen-doped carbon coating.

The epitaxial growth of high-quality thin films provides a powerful method for the rapid preparation of new materials and discovery of materials with promising properties. Here, we report the effect of substrate temperature on the epitaxial growth of high-quality and large-area epitaxial CdTe films on GaAs(100) by molecular beam epitaxy. RHEED patterns as a function of the substrate temperature showed sharp streaky lines. A CdTe epilayer grown at 320 °C showed the narrowest full-width at half-maximum (FWHM) of 180 arcsec from (004) reflection in X-ray rocking curve measurements. The smooth and flat surface observed in the AFM image showed the excellent uniformity of the thin film, and the surface roughness decreased monotonically with the substrate temperature. From the substrate temperature dependence of the (A0, X) emission line, the luminescence intensity was found to increase with increasing substrate temperature, while the FWHM decreased with substrate temperature. Our experimental data suggest that the substrate temperature plays an important role in establishing hetero-epitaxial film growth for semiconductor devices.

Flexible batteries have gained significant attention in recent years, owing to their huge demand for portable wearable electronics and smart fabrics. However, conventional Li-ion batteries (LIBs) have limited device adaptability because of their planar architecture. To address this issue, the LIBs are shrunk to a one-dimensional fiber shape, which provides the freedom and flexibility needed for their integration with wearable electronics and smart fabrics. Herein, we demonstrate a method to fabricate twisted yarn-type (TYT) LIBs by a direct ink writing-based three-dimensional printing technology, using natural graphite and LiNi0.6Co0.2Mn0.2O2 as anode and cathode active materials, respectively, along with vapor-grown carbon fibers as an integrated conductive matrix. The printed electrode fibers are twisted together to create anode and cathode yarns, which are then assembled together to obtain a prototype TYT LIB device. The fabricated device performs significantly better in terms of both electrochemical performance and flexibility. The proposed method thus enables the direct integration of batteries into commercial fabrics either in the form of individual electrodes or full devices, which opens up a new route for developing next-generation energy storage devices for smart fabrics.

We demonstrate the structural evolution of polymorphic phases in Al2O3-inserted SrMnO3 ceramics synthesized by solid state reaction. While the 4H-hexagonal phase is predominant in pure SrMnO3 ceramics, a small amount of 6H-hexagonal polymorph is identified in addition to the primary 4H-hexagonal SrMnO3 and the secondary hexagonal SrAl2O4 phases in the as-sintered ceramics, evidenced by x-ray diffraction and subsequent Rietveld refinement analyses. The existence of the 6H-hexagonal SrMnO3 phase is corroborated using Raman spectroscopy. The chemical compositions and electronic structures of the Al2O3-inserted SrMnO3 compounds are also examined using energy dispersive spectroscopy and x-ray photoelectron spectroscopy, respectively. The first-principles calculations reveal that there is no clear difference between the total energies of 4H- and 6H-hexagonal polymorphs regardless of the presence/absence of Sr and oxygen vacancies. Possible origins are discussed with the estimation of actual strain based on the refined lattice parameter of 6H SrMnO3.

In this study, lead-free zirconium (Zr)-modified Bi1/2(Na0.78K0.22)1/2TiO3 (BNKT) ceramics were synthesized by the conventional solid-state reaction method. The co-existence of two phases (tetragonal; P4mm and cubic phases; Pm 3 ‾ m) with definite phase fractions were observed for all samples. The lattice parameters were gradually enhanced by the addition of Zr-content in the BNKT ceramics, which strongly support the relaxor-ferroelectric response. All of the samples are well-dense with no noticeable pores detected. Definite grains with clear grain boundaries were observed through SEM analysis. The temperature-dependent (25–200 °C) ferroelectric polarization response of all specimens were studied in detail under the constant applied electric field (60 kV cm-1). Thermally-stable high energy-storage properties (Wrec ≈ 0.72 J cm-3, and η ≈ 98%) with an extended operating temperature range (25–200 °C) within ±15% variation was observed for the Zr-modified BNKT composition. The enhancement of energy-storage properties can be attributed to the Zr addition, which increased the phase fraction of cubic crystal structure and assisted the ferroelectric to relaxor-ferroelectric phase transition. This study provides a comprehensive analysis of the energy-storage response of the lead-free ceramics for energy-storage devices.

It is demonstrated experimentally and confirmed theoretically that highly defective boron nitride showed outstanding performance for oxidative dehydrogenation of ethylbenzene. The catalyst is derived from carbon-doped hexagonal boron nitride nanosheets synthesized via a two-step reaction when participating the oxidative dehydrogenation reaction. The first step yields a polymeric precursor with the atomic positions of B, C, N relatively constrained, which is conducive for the formation of carbon atomic clusters uniformly dispersed throughout the BN framework. During the oxidative dehydrogenation of ethylbenzene to styrene, the nanoscale carbon clusters are removed and highly defective boron nitride (D-BN) is obtained, exposing boron-rich zigzag edges of BN that act as the catalytic sites. The catalytic performance of D-BN is therefore remarkably better than un-doped h-BN. Our results indicate that dispersed C-doping in h-BN is highly effective in terms of defect formation and resultant enhanced activity in oxidative dehydrogenation reactions.

Metal (M) contact with a semiconductor (S) introduces metal-induced gap states (MIGS), which makes it difficult to study the intrinsic electrical properties of S. A bilayer of metal with graphene (Gr), i.e., a M/Gr bilayer, may form a contact with S to minimize MIGS. However, it has been challenging to realize the pristine M/Gr/S junctions without interfacial contaminants, which result in additional interfacial states. Here, we successfully demonstrate the atomically clean M/Gr/n-type silicon (Si) junctions via all-dry transfer of M/Gr bilayers onto Si. The fabricated M/Gr/Si junctions significantly increase the current density J at reverse bias, compared to those of M/Si junctions without a Gr interlayer (e.g., by 105 times for M = Au in Si(111)). The increase of the reverse J by a Gr interlayer is more prominent in Si(111) than in Si(100), whereas in M/Si junctions, J is independent of the type of Si surface. The different transport data between M/Gr/Si(111) and M/Gr/Si(100) are consistent with Fermi-level pinning by different surface states of Si(111) and Si(100). Our findings suggest the effective way to suppress MIGS by an introduction of the clean Gr interlayer, which paves the way to study intrinsic electrical properties of various materials.

The energy storage performance of lithium-ion batteries (LIBs) depends on the electrode capacity and electrode/cell design parameters, which have previously been addressed separately, leading to a failure in practical implementation. Here, we show how conformal graphene (Gr) coating on Ni-rich oxides enables the fabrication of highly packed cathodes containing a high content of active material (~99 wt%) without conventional conducting agents. With 99 wt% LiNi0.8Co0.15Al0.05O2 (NCA) and electrode density of ~4.3 g cm-3, the Gr-coated NCA cathode delivers a high areal capacity, ~5.4 mAh cm−2 (~38% increase) and high volumetric capacity, ~863 mAh cm-3 (~34% increase) at a current rate of 0.2 C (~1.1 mA cm-2); this surpasses the bare electrode approaching a commercial level of electrode setting (96 wt% NCA; ~3.3 g cm-3). Our findings offer a combinatorial avenue for materials engineering and electrode design toward advanced LIB cathodes., Li-ion battery electrodes contain inactive materials, such as conducting agents and polymeric binders, which limit the energy density. Here, the authors demonstrate highly dense Ni-rich cathodes with improved volumetric capacities by coating graphene and minimizing the inactive components.

The effects of CaTiO3 (CT) and BaZrO3 (BZ) modification upon the crystal structure and electromechanical properties of lead‐free Bi0.5Na0.5TiO3–SrTiO3 piezoelectric ceramics were compared within a doping range of 0–4 mol%. The different effects of CT and BZ modification upon the phase transition are clearly observed in the polarization and strain hysteresis loops. The CT‐modified specimens maintain strong ferroelectricity without any abnormal enhancement in the electric field‐induced strain. However, the addition of as little as 1 mol% BZ induces a transition from a nonergodic relaxor phase to an ergodic relaxor phase, thus resulting in disruption of the ferroelectric order and the generation of a high field‐induced strain. The present authors believe that the substitution of large ions (such as Zr4+) into the B‐sites, rather than the A‐sites, of the Bi0.5Na0.5TiO3‐based ceramics plays a significant role in the phase transition behavior.

This study investigated the phase transition behavior and electrical properties of (K0.5Na0.5)(Nb1-xZrx)O3 (KNN‒100xZ) and (K0.5Na0.5)NbO3–yBaZrO3 (KNN–100yBZ) lead–free piezoelectric ceramics. The phase transitions in crystal structures were compared in KNN ceramics between single Zr4+ doping and Ba2+Zr4+ co−doping. Piezoelectric properties such as the piezoelectric constant (d33) and electromechanical coupling factor (kp) are optimized for KNN‒6BZ ceramics and were clarified via the polymorphic phase transition from the orthorhombic to pseudocubic phase. The fitted degree of diffuseness (γ) for a phase transition from the modified Curie–Weiss law indicated that KNN ceramics as ferroelectrics are gradually transformed through BaZrO3 modification. Accordingly, the enhanced strain properties at y = 0.08 consist of coexisting ferroelectric domains and polar nanoregions that are supported by ferroelectric–to–relaxor crossover in KNN‒100BZ ceramics.

In this article, a feasibility study on an optically transparent planar dipole antenna using liquid salt water at wide ultra-high frequency (UHF) band (470–771 MHz) for application in external antenna of ultra-high-definition television (UHD TV) is presented. The most significant reason behind using liquid salt water for transparent antenna applications is its excellent average optical transparency (OTav) (>95% at salinity of 40 ppt) compared with other typical solid transparent thin-film electrodes such as indium tin oxide (>73%) or multilayer films (>78%). Each conductive arm of the proposed dipole is constructed from a salt-water layer held between two clear planar acrylic layers ( $\varepsilon _{r} = 2.61$ , tan $\delta = 0.01$ , OTav > 90%) (acrylic/salt water/acrylic; ASA) due to surface tension. To investigate the electrical and optical properties of the ASA structure, we analyze the surface tension to determine the thickness of the salt-water layer that finalizes its sheet resistance and OTav. The average gain and efficiency of the antenna are 1.72 dBi and 74%, respectively, in the operating UHF band. This makes the proposed antenna a good candidate for application as a transparent external antenna in UHD TVs and proves that it is possible to use salt water for high-frequency devices.

Ni-rich LiNi0.8Co0.1Mn0.1O2 (NCM811) is regarded as a potential cathode material due to its higher capacity. However, the severe capacity fading which occurs above 4.2 V vs. Li/Li+ needs to be addressed to enhance the electrochemical performance. Herein, we report the surface modification of NCM811 cathodes with a perovskite material, i.e., lanthanum iron oxide (LaFeO3), which has drawn attention for various research areas due to its non-toxicity, electric conductivity, chemical stability, and low cost and systematically investigate the influence of the LaFeO3 coating on NCM811. The LaFeO3 coating layer significantly protects the cathode material from corrosion due to the HF formation and restrains the dissolution of other ions into liquid electrolyte during high voltage charge–discharge processes. Even after 80 cycles, 0.5 wt% LaFeO3-coated NCM811 cathode material shows about 13% higher cycling stability when compared to the bare NCM811 and other ratios of coated materials. Furthermore, the 0.5 wt% LaFeO3-coated NCM811 delivers excellent rate capability and demonstrates improved structural stability at 4.6 V vs. Li/Li+ under high voltage conditions with Ni-rich cathode active materials.

Lead-free (Bi0.5Na0.5)(Ti1-xMnx)O3 (BNTMn-x; x = 0, 0.0025, 0.0050, 0.0100) thin films were fabricated using a chemical solution deposition method on Pt/TiO2/SiO2/Si substrate. The effect of Mn substitution on crystal structures, surface morphologies, and ferroelectric and transverse piezoelectric properties of BNTMn-x thin films was investigated. The 0.5 mol% Mn-doped (Bi0.5Na0.5)(Ti0.995Mn0.005)O3 thin film exhibited a well-saturated ferroelectric P-E hysteresis loop at room temperature. A remnant polarization (Pr) of 16 μC/cm2 was obtained for the BNTMn-0.0050 film at an applied electric field of 400 kV/cm. In addition, a 1.12-μm-thick BNTMn-0.0050 film was applied as a cantilever. The Pt/BNTMn-0.0050/Pt/TiO2/SiO2/Si unimorph cantilever exhibited a high transverse piezoelectric coefficient ( e 31 ∗ ) of 2.43 C/m2.

The formation of a morphotropic phase boundary (MPB) in piezoelectric ceramics is one of the most important techniques to enhance their dielectric and piezoelectric properties. In this work, a rhombohedral (R) and tetragonal (T) phase boundary has been designed and clarified using the lead‒free 0.92(Na0.5K0.5)NbO3–(0.08–x)(Bi0.5Li0.5)TiO3–xBaZrO3 ternary system. The R-T phase coexistence region is identified in the ceramics with 0.06 ≤ x ≤ 0.07. We successfully demonstrated that the crystal’s relatively enhanced d33 and its excellent temperature stability are originated from phase transition behaviors that were confirmed by the temperature‒dependent dielectric properties and X−ray diffraction (XRD) patterns.

Bismuth-based lead-free ceramics are some of the most promising candidates for actuator applications due to their large strain response. Despite the large strains in bismuth-based piezoelectric ceramics, there still remain challenges regarding their utilization in practical applications. For instance, a relatively high operating field is required to obtain the large strain properties. In this work, lead-free Bi1/2Na1/2TiO3-SrTiO3-BiAlO3 (BNT-ST-BA) ternary piezoelectric ceramics are proposed as materials that could enhance the electromechanical strain performance under low driving field. We found that the highest normalized strain d33* value of 707 pm/V was achieved at a relatively low electric field of 3 kV/mm from 2 mol.% BA-modified BNT-ST ceramics. We suggest that the naturally induced nonergodicities in the ergodic relaxor generate internal stress. This induced internal stress is responsible for the excellent strain properties of this material. We believe that the materials synthesized in this study are promising candidates for actuator applications.

Carbon nanotubes (CNT) have been widely used as catalyst supports, and the confinement of metal nanoparticles inside the CNT cavity have received much attention. In this study, graphitic carbon nitride were used to introduce nitrogen to CNT and form ruthenium nanoparticles inside the CNT channel. The XPS evidenced that the ruthenium nanoparticles in the CNT cavity are present in more reduced state, and the nitrogen species are in a pyridinic and a pyrrolic form. The prepared catalysts exhibited excellent hydrogen and carbon monoxide selectivity. The hydrogen-to-carbon monoxide ratio was close to the stoichiometric ratio of methanol decomposition. In contrast, the ruthenium nanoparticles outside the CNT showed lower carbon monoxide selectivity at high methanol conversion. The alteration of electrical properties of ruthenium nanoparticles by the CNT channel and N-doping might hamper side reactions, such as water gas shift, methanation, dimethyl ether formation upon methanol decomposition.

Hydrogen energy is a potential next-generation energy source for fossil fuel replacement. The development of high-efficiency materials and catalysts for storage and transportation of hydrogen energy must be achieved to realize hydrogen economy. Recently, catalyst systems such as Pd nanoclusters (Pd NCs) supported on nickel hydroxide (Ni(OH)2) have been reported to have advantages, including effective suppression of CO production and efficiency enhancement of HCOOH dehydrogenation. However, the reaction mechanism and multi-metallic interface system design of such systems have not been elucidated. Therefore, various Ni(OH)2 surfaces supported on a graphene system were designed through density functional theory calculations, and the support material was combined with Pd38NC (Pd38NC/Ni(OH)2-G). Subsequently, the adsorption behavior of HCOOH dehydrogenation intermediates was analyzed. We found a new adsorption configuration in which HCOOH* (where * and a single underline indicates the adsorbed species and adsorbed atom, respectively) was adsorbed in a more stable manner (adsorption energy, Eads= −1.22eV) on the system than HCOOH* (Eads=−1.10eV) owing to the presence of Ni(OH)2-G. This affected the next step in HCOOH dehydrogenation, i.e., formation of HCOO* species, and showed a positive effect on the HCOOH dehydrogenation. To fundamentally understand this phenomenon, electronic structure (d-band center and density of states) and stability (vacancy formation energy) analyses were performed.

A typical microwave oven generates an electromagnetic wave in an ISM band of 2.45 GHz. To prevent this unwanted microwave leakage through its front door, a circular perforated metal sheet is typically used with low shielding effectiveness ( RS ) and optical transparency (OT) for electrical and optical performance of two transparent electrodes (TEs) including metal mesh film (MMF) and indium tin oxide (ITO) and compare those to the currently used perforated copper sheet (PCS) in commercial microwave oven. The measured RS and average OT in visible spectrum of MMF is 0.11 Ω/sq and 68.4%, and its figure of merit (FoM) is 203.8 which is the highest among them. The measured shielding effectiveness of MMF, ITO, and PCS at 2.45 GHz are 31.4, 21.0, and 25.5 dB, respectively. The results indicate that MMF has highest FoM and the best EMC performance among the TEs and PCS, which makes it the most suitable candidate for microwave ovens.

Micron-sized Ni–Al alloy powders (Ni–x wt.%Al, x = 40, 50, 60) were synthesized using the low-temperature chemical alloying (LTCA) at 500 °C. The three different as-prepared Ni–Al alloy powders were composed of Ni2Al3 and/or NiAl3 phases while achieving thermodynamic equilibrium compositions (Ni–40 wt%Al, Ni2Al3; Ni–50 wt%Al, the coexistence of Ni2Al3 and NiAl3; Ni–60 wt%Al, NiAl3). The LTCA method demonstrates that it is capable of producing Al-rich Ni–Al alloy powders while maintaining a particle size similar to that of the starting Ni particles. The three Ni–Al alloy powders were used as precursor materials to fabricate porous nickel catalysts through a selective aluminum leaching process, followed by the enlargement of the surface area. Alteration of the material characteristics with respect to the leaching time was investigated using XRD, FESEM-EDS, TEM, XPS, TPR, BET, and particle size analysis. The nickel skeletal catalysts with the increased BET-surface areas (50–111 m2/g) displayed high reactivity toward ammonia decomposition.

Formate received a significant attention as storing H2 in chemical bonds to the concept of H2 carriers. In this report, hydrogen generation from formate was optimized systematically by varying reac...

Despite intensive studies on van der Waals heterostructures based on two-dimensional layered materials, isotype vdW heterojunctions, which consist of two different semiconductors with the same majority carrier, have received little attention. We demonstrate an n–n isotype field-effect heterojunction device composed of multilayer moly ditelluride (MoTe2) and tin disulfide (SnS2). The carrier transport flowing through the n-MoTe2/n-SnS2 heterojunction exhibits a clear rectifying behavior exceeding 103, even at a moderate source–drain voltage of 1 V in ambient environment. Owing to the large band offsets between the two materials, a potential barrier exceeding ~1 eV is formed, which is verified by comparing a numerical solution of Poisson’s equation and experimental data. In contrast to the conventional p–n heterostructure operating by diffusion of the minority carrier, we identify the carrier transport is governed by the majority carrier via the thermionic emission and tunneling-mediated process through the potential barrier. Furthermore, the gate voltage can completely turn off the device and even enhance the rectification. A ternary inverter based on the isotype MoTe2/SnS2 heterojunction and a SnS2 channel transistor is demonstrated for potential multivalued logic applications. Our results suggest that the isotype vdW heterojunction will become an able candidate for electronic or optoelectronic devices after suitable band engineering and design optimization.

This study investigated the structures, dielectric, ferroelectric and piezoeletric properties of lead-free (0.99‒x) Bi0.5Na0.5TiO3‒0.01CaTiO3‒xSrTiO3 (BNT‒CT‒100xST, x = 0.22–0.30) piezoelectric ceramics. These piezoceramics were successfully prepared using the conventional solid-state reaction method sintered at 1175 °C for 2 h. It was found that a phase transition from nonergodic relaxor to ergodic relaxor was induced by ST modification in BNT‒CT ceramics. Consequently, a large electromechanical strain of 0.20% corresponding to high normalized strain $$d_{33}^{*}$$ of 667 pm/V was obtained even under 3 kV/mm for BNT‒CT‒28ST ceramics. Therefore, it is noted that lead-free BNT‒CT‒100xST ceramics can be promising candidates for actuator applications.

In this study, aqueous phase reforming (APR) of xylose was conducted over highly dispersed Pt nanoparticles supported on a γ-Al2O3 support (Pt-SNP). Formation of small Pt nanoparticles was confirmed by X-ray diffraction and transmission electron microscopy, which revealed that most of the particles ranged between 0.8 and 1.6 nm in size and the average particle size was 1.3 nm. Temperature-programmed reduction analysis indicated that these small Pt nanoparticles were highly reducible under the reducing environment compared to the commercial Pt/γ-Al2O3 catalysts (Pt-commercial). The catalytic activities of both Pt-SNP and Pt-commercial catalysts were examined in a semi-batch autoclave reactor system for the APR of xylose. It was found that Pt-SNP showed higher carbon to gas conversion with high hydrogen selectivity than Pt-commercial. This was likely due to the increased density of edge sites in the Pt-SNP catalyst that facilitated the cleavage of the C–C bonds rather than the C–O bonds, leading to greater hydrogen production. Furthermore, the Pt-SNP catalyst showed better carbon deposit resistance as compared to Pt-commercial. The amount of carbon deposition on the Pt-SNP catalyst surface and the organic carbon species dissolved in the post-reaction xylose solution were significantly lower compared to that of Pt-commercial. Finally, high purity hydrogen production was achieved using a continuous fixed-bed hybrid reactor including an aqueous phase reformer and a home-made Pd/Ta dense metallic composite membrane. A stable hydrogen gas production (99.999%) was obtained over the Pt-SNP catalyst, which demonstrated the success of a potentially commercial APR reactor system that continuously converted the aqueous xylose solution to hydrogen with high purity.

Hydrogen storage in Liquid Organic Hydrogen Carrier (LOHC) systems is appealing for the safe storage and distribution of excess renewable energy via existing gasoline infrastructures to end-users. We present the eutectic mixture of biphenyl and diphenyl ether of its first use as a LOHC material. The material is hydrogenated with 99% selectivity without the cleavage of C O bond, with commercial heterogeneous catalysts, which is confirmed by nuclear magnetic spectroscopy and gas chromatography-mass spectrometry. Equilibrium concentration, dehydrogenation enthalpy, and thermo-neutral temperature are calculated using a density functional theory. The results indicate that O-atom-containing material exhibits more favorable dehydrogenation thermodynamics than that of the hydrocarbon analogue. The H2-rich material contains 6.8 wt% of gravimetric hydrogen storage capacity. A preliminary study of catalytic dehydrogenation on a continuous reactor is presented to demonstrate a reversibility of this material.

Carbon-based electrocatalysts for oxygen reduction reaction (ORR), especially in anion exchange membrane fuel cells (AEMFCs), have received a lot of attention because they exhibit excellent stability and are comparable to commercial Pt/C catalysts. Currently, to maximize the catalytic activity of carbon-based electrocatalysts, there are two major strategies: heteroatom doping or exposing active edge sites. However, the approach of increasing heteroatomic dopants of active edge sites has been rarely addressed. In this study, we present a simple strategy to prepare edge-enriched graphene catalysts with an increased ratio of heteroatomic dopants suitable for ORR of AEMFCs. The catalysts were prepared under harsh oxidation conditions, followed by a simple co-doping process with boron and nitrogen. The ORR activity of the catalysts was observed to be related to an increase of edge sites with heteroatomic dopants. We believe that the edge-enriched structure leads to accelerated electron transfer with enhanced oxygen adsorption.

In this perspective article, the synthesis and thermodynamic properties of aqueous solutions of formate salts (FS, HCO2−) are described in relationship to the concept of H2 carriers. The physiochemical properties of solid FS, aqueous formate solutions, and aqueous bicarbonate solutions set the limitations for storage capacity, deliverable capacity, and usable H2 capacity of these H2 carriers, respectively. These parameters will help in the design of systems that use H2 carriers for storage and transport of H2 for fuel cell power applications. FS, as well as admixtures with formic acid (FA, H2CO2), have potential to address the goals outlined in the U.S. Department of Energy's H2@scale initiative to store in chemical bonds a significant quantity of energy (hundreds of megawatts) obtained from large scale renewable resources.

We demonstrate a practical way to identify the presence of a perovskite phase in rare-earth nickelates (RNiO3) using X-ray photoelectron spectroscopy (XPS). By varying the calcination temperature, we prepared RNiO3 powders with different degrees of chemical reaction. We found that perovskite RNiO3 becomes predominant after high-temperature calcination (≥1,000 °C) in X-ray diffraction and XPS (at Ni 3p and O 1s edges) measurements. While the observed spectra at the Ni 3p edge are similar for all powders, a sizable difference was observed in the O 1s-edge spectra depending on the calcination temperature. With the formation of a perovskite phase with a trivalent Ni3+ state, an XPS peak corresponding to oxygen ions in the perovskite lattice distinctly emerges. Our work shows that the Ni3+ state cannot be determined by analyzing the Ni 3p edge solely and rather, the O 1s edge should be simultaneously monitored for explicit identification.

We use a strategy to reduce the driving electric field of the relaxor 0.72Bi1/2Na1/2TiO3–0.28SrTiO3 (BNT–28ST) by introducing ferroelectric plate–type Bi1/2(Na0.78K0.22)1/2TiO3 (BNKT) particles. Consequently, 10 vol.% BNKT added BNT–28ST/BNKT (relaxor/ferroelectric) composite has delivered large normalized strain (Smax/Emax = 650 pm/V) under relatively low applied field of 2.5 kV/mm with the reduction in the poling field value to 36% compared to that of pure BNT–28ST ceramics. We demonstrated that such behavior comes from the stress induced effect at the boundary of the ferroelectric and relaxor materials due to their different nature (relaxor/ferroelectric). The generation of stress is expected from the ferroelectric (BNKT) to the relaxor (BNT–28ST) at the boundary. Thereby, field–dependent stress at relaxor/ferroelectric phase boundary is monitored proposing the reduction of the poling field due to the strain coupling mechanism. Our findings provide a pathway for reducing the poling field in BNT–based incipient piezoelectric ceramics.

This paper presents a highly optical transparent and tunable liquid antenna for applications on the UHF band. The antenna has high transparency (> 91%), which is achieved through its use of salty water as a conductive medium held within a clear and hollow acrylic rectangular prism, allowing its use as an optical window. To achieve frequency- and beam-tunable characteristics, two advanced configurations of the antenna using dual-port feeding are proposed. The antenna’s performance is simulated and then verified through experiments. Measurement results show that for a basic configuration using single-port feeding, the antenna has a −6 dB bandwidth ranging from 350 to 675 MHz and efficient radiation efficiency (> 60%) over the band. For advanced configurations, a tunable frequency and directional radiation pattern can be achieved with enhancing gain compared to the basic configuration. These results demonstrate the proposed antenna can be used as a bi-functional device, i.e., as atunable antenna and optical window.

We have demonstrated both interference and diffraction of a pseudo-double slit using two glass plates with a width and a length of about 5 cm and a thickness of about 5 mm. The plates are attached at the upper and lower ends with Scotch tape of about 0.1 to 0.3 mm between the plates. By adjusting the angle between the two plates, we are able to demonstrate a single-slit diffraction pattern or a double-slit interference pattern. Also we can simulate a changing separation between slits by changing the angle between the plates.

Connexin family proteins assemble into hexameric hemichannels in a cell membrane, which dock together between two adjacent membranes to form gap junction intercellular channels (GJIChs). The most ubiquitously expressed connexin Cx43 plays important roles in numerous biological processes. Here we report cryo-EM structures of Cx43 GJIChs at 3.1–3.6 Å resolutions, which show dynamic conformational changes of N-terminal helices (NTHs) caused by pH change or C-terminal truncation. Cx43 GJIChs in a channel-closing condition contain 12 protomers in gate-covering NTH (GCN) conformation, while those in opening conditions have varying compositions of GCNs and pore-lining NTHs (PLNs) resulting in various pore dimensions and electrostatic surface potentials. GCN-to-PLN transition accompanies π-helix formation in the first transmembrane helix (TM1), movement of TM2-4 that creates a side opening to the membrane, and structural stabilization of the cytoplasmic loop. Our study provides structural insights into the intercellular ion/metabolite transfer and the lateral lipid transport through Cx43 GJICh.

Great potential for improvements in engineering photonic applications is seen in topological photonic systems due to facilitated single mode operation and since the inherent topological protection might make them more robust to imperfections in design and fabrication [1] . There have been recent demonstrations of lasing in suspended 1D nanobeam structures based on a topological cavity, where the suspension leads to a high-Q cavity enabling efficient lasing [2] . In an actual integrated system, however, structures would ideally be embedded in oxide, which will inevitably reduce the refractive index contrast (n>1) and therefore lead to a lower Q.

Topological photonics have emerged as a framework to manipulate light for low-loss and compact photonic applications, such as waveguides, beam splitters, isolators, and lasers, due to their immunity to imperfections or structural disorder in bulk [1] . One-dimensional topological photonic crystals (1D-PhCs), particularly, have received great attention due to their simple architecture, convenient fabrication process, and relatively easy prediction of their optical characteristics using standard simulation methods. Recently, a topological nanocavity laser with high Q factors of over 10,000 was demonstrated at the interface between two topologically distinct 1D photonic crystals (PhC) [2] .

Pd-based bimetallic nanoparticles have superior electrochemical activity and stability for formic acid oxidation (FAO) than pure Pd. Previous DFT-based calculations show that the catalytic properties of the Pd surface could be altered by modifying its electronic properties. However, only a few experimental studies investigate how the electronic properties of Pd are modified by introducing various metals and how the resulting electronic perturbation affects its electrochemical activity and stability for FAO. Here, we demonstrate a correlation between electrochemistry and electronic properties for Pd-M bimetallic nanoparticles (M = Ru, Pt, Cu, Au, and Ag). The volcano shape relationship obtained between activity and d-band center values suggests that the electronic effects play a major role in modifying the surface electrochemical properties of Pd-M bimetallic nanoparticles for FAO. Among all the bimetallic catalysts investigated in this study, Pd-Pt/C and Pd-Cu/C with d-band center values of 2.58 eV and 2.85 eV, respectively, demonstrate the highest activities and Pd-Cu/C exhibits the highest stability for FAO.

We demonstrate a phase transition between BaTiO3 polymorphs induced by Ni substitution experimentally. The structural evolution of tetragonal-to-hexagonal polymorph in Ni-doped BaTiO3 ceramics is observed macroscopically and then, visualized in an atomic scale. Under this structural transition, the long-range ferroelectric ordering in the undoped BaTiO3 with tetragonal symmetry is suppressed and eventually, vanishes in the heavily Ni-doped BaTiO3 with hexagonal symmetry and dielectricity. An oxygen vacancy defect can be created at a local Ni doping site with a decrease in the charge valence state from Ti4+ (3d0) to Ti3+ (3d1). With the reduction of the Ti4+ oxidation state, the polar Ti–O ionic displacement is degenerated in the tetragonal BaTiO3 and thereby, the short-range Coulomb repulsion may be restored in the hexagonal BaTiO3 resulting in a polymorphic phase transition. Our work is of potential interest for artificial realization of an exotic phase in complex oxide materials by doping.

We demonstrate the effect of the crystallinity of ceramic targets on the electronic properties of LaNiO3 (001) thin films epitaxially grown by pulsed laser deposition (PLD). We prepared two kinds of LaNiO3 targets with different crystallinity by manipulating calcination temperature (i.e., 300 and 1000 °C) in the solid state reaction for ceramic synthesis. X-ray diffraction (XRD), field emission-scanning electron microscopy (FE-SEM), and X-ray photoelectron spectroscopy (XPS) experiments of the as-sintered LaNiO3 ceramic targets clearly show that the LaNiO3 target sintered after high-temperature (1000 °C, high crystallinity) calcination is more oxidized to Ni3+ with better crystallinity than the LaNiO3 target sintered after low-temperature (300 °C, poor crystallinity) calcination. Using these two LaNiO3 ceramics as PLD targets, we fabricated epitaxial LaNiO3/LaAlO3 (001) thin-film heterostructures to examine how target crystallinity affects the physical properties of LaNiO3 films. Intriguingly, the electri...

This study investigated the structures, dielectric, ferroelectric and piezoelectric properties of (0.99‒x)Bi1/2Na1/2TiO3‒0.01KTaO3‒xSrTiO3 (BNT‒KT‒100xST, x = 0.20 ˜ 0.235) lead‒free piezoelectric ceramics. These piezoceramics were synthesized by conventional solid‒state reaction method. As a consequence, a large electrical strain and normalized strain (d33* ≈ 793 pm/V) can be obtained even under 3 kV/mm as low electric field for BNT‒KT−22.5ST ceramics. The phase transition between nonergodic relaxor (NER) and ergodic relaxor (ER) under electric field might be responsible for its large strain. It means that BNT‒KT‒100xST lead‒free ceramics can be a promising candidate for actuator applications.

To realize giant electrostriction in BNT-based piezoelectrics, the tuning of thermotropic phase boundary (TF-R) towards ambient temperature is necessary. For the regulation of such TF-R, compositional modification approach either in the form of elemental doping or the substitution of higher tolerance factor ABO3 perovskite is usually preferred. In this study, we used a feasible approach to tune the TF-R of BNT-based system by introducing low tolerance factor ABO3 perovskite to achieve large strain response. To assess our synthetic approach, herein, a novel low tolerance factor perovskite Bi(Zn1/2Ce1/2)O3 is introduced as a chemical modifier and a ternary (0.935-x)Bi1/2Na1/2TiO3-0.065BaTiO3-xBi(Zn1/2,Ce1/2)O3 (BNT-BT-BZC) system is designed and prepared by solid state reaction method. By monitoring the temperature-dependent permittivity and tangent loss, a critical composition is detected for x = 0.015, at which the TF-R tuned down to room temperature (RT). By establishing the relationship between TF-R and electromechanical strain, the composition (x = 0.015) where TF-R situated below RT showed highest strain response (S = 0.43%) accompanied by a giant electrostrictive coefficient Q33 ˜0.036 m4/C2. The derived Q33 value is comparable to the prominent Pb-based counterparts and much higher than the reported lead-free BNT-based electrostrictors. Furthermore, favorable temperature stability in strain and electrostrictive performances is also demonstrated for the BNT-BT-BZC compound. We expect that our current work may provide a highly attractive way for the future development of lead-free electrostrictive materials.

In this study, hexagonal boron nitride nanosheets (h-BNNS) have been grown on polycrystalline silver substrates via chemical vapor deposition (CVD) using ammonia borane as a precursor. The h-BNNS are of few-atomic-layer thickness and form continuous coverage over the whole Ag substrate. The atomically thin coating poses negligible interference to the reflectivity in the UV–visible range. The nanosheet coating also proves very effective in protecting Ag foil chemically. In contrast to bare Ag foil, the coated foil displayed only minor decolorization under high concentration of H2S. The study indicates that h-BNNS can be a promising protective coating for Ag based items such as jewelry or mirrors used in astronomical telescopes.

Reversible formate (HCOO–) dehydrogenation and bicarbonate (HCO3–) hydrogenation would be desirable for the utilization and storage of hydrogen (H2) as an effective energy carrier. Carbon-supported Pd-based nanoparticles demonstrated enormous competitive advantages for these reactions. However, the fundamental mechanisms underlying these reversible reactions have not yet been elucidated. Herein, we report the reaction pathways for reversible reactions on a Pd-based catalyst using density functional theory (DFT) calculations and propose key factors for improving the reaction efficiency. As the first essential step, the difficulty in the conventional DFT modeling, that is simulation of an anion environment caused by HCOO–, was overcome by designing two-sided Pd12 nanoclusters supported on graphene (Pd12NC-G) with extra electrons. Using Pd12NC-G, we demonstrated that the key factor determining the potential limiting steps for the reversible reaction was desorption of hydrogen in HCOO– dehydrogenation (1.24 e...