FT infrared study of Brønsted acidity of H-mordenites: Heterogeneity and effect of dealumination

Pyridine adsorption on the parent mordenite (Si/Al= 10.7) showed that the 3,610 cm⁻¹ OH band presents two components: one at 3,612 cm⁻¹, corresponding to OH groups in the main channels; the other, at 3,585 cm⁻¹, inaccessible to pyridine, attributed to OH groups in the side pockets. CO adsorption showed that the high-frequency groups are more acidic (Δν_OH = 332 cm⁻¹; ν_CO = 2,177 cm⁻¹) than the latter (Δν_OH = 260 cm⁻¹; ν_CO = 2,169 cm⁻¹). Steaming at 930 K followed by acid leaching modified the structure, making the low-frequency OH groups accessible to pyridine. CO adsorption still evidenced the heterogeneity of the Brønsted acid sites whose origin is discussed. This study specifies the assignment of a band occasionally observed at 3,660 cm⁻¹. It corresponds to water adsorption on acidic OH groups.     

Coordination of Ni2+ to lattice oxygens of the zeolites X and Y

The coordination of Ni²⁺ to lattice oxygens of zeolites X and Y has been studied for a series of NiCaX, NiCaY, NiLaX and NiLaY zeolites. There are 3 types of coordination. Octahedral coordination for Ni²⁺ in hexagonal prisms occurs in all zeolites. The characteristic dd bands are located at 6100–6400 cm⁻¹, 10 300–10 650 cm⁻¹ and 19 000–20 000 cm⁻¹. The corresponding octahedral ligand field strength parameter 10 D_qo is 6100–6400 cm⁻¹ and Racah's electronic repulsion parameter B is 696–801 cm⁻¹. Ni²⁺ in tetrahedral coordination with 3 lattice oxygens and one extra-lattice oxygen has a characteristic dd band at 8200 cm⁻¹ and a doublet at 16 100 and 17 500 cm⁻¹. 10 D_qt is 4460 cm⁻¹ and B is 916 cm⁻¹. This tetrahedral Ni²⁺ is predominant in NiLaX zeolites, but occurs also to a lesser extent in NiLaY and in NiCa zeolites. It is formed at the expense of trigonal Ni²⁺ on site l' with a dd band at 4900 cm⁻¹, 9000–9500 cm⁻¹ and 21 500–23 500 cm⁻¹. This trigonal spectrum is the same as in A-type zeolites. This indicates that, from the viewpoint of coordination the six-rings of oxygen of A, X and Y zeolites are very similar.     

Evidence for the presence of superacid nonframework hydroxyl groups in dealuminated HY zeolites

The presence of a hydroxyl i.r. band at 3610 cm⁻¹ that interacts with pyridine at desorption temperatures up to 400°C is detected in dealuminated HY zeolite and tentatively assigned to an amorphous silica—alumina phase, formed upon dealumination.     

Infrared spectroscopy,thermoprogrammed desorption,and nuclear magnetic resonance study of the acidity,structure, and stability of zeolite MCM-22

Zeolite MCM-22 has been studied by infrared (i.r.) spectroscopy, thermoprogrammed desorption (t.p.d.) of NH₃, and²⁷Al n.m.r. with magic angle spinning (MAS). It has been found that zeolites MCM-22 and ZSM-5 both have framework i.r. bands at about 1,245 and 550 cm⁻¹, and zeolites MCM-22 and Y both have two pore opening i.r. bands at about 380 and 317 cm⁻¹. In MCM-22 there are two kinds of bridged hydroxyls (3,620 and 3,575 cm⁻¹) and two kinds of internal silanols (3,500 and 3,700 cm⁻¹). The latter two i.r. frequencies are similar to those in zeolites ZSM-5 and Y, respectively.²⁷Al n.m.r. reveals two kinds of framework tetrahedral Al. The spectroscopic similarities and the dual appearance of the relevant i.r. bands/n.m.r. peaks seem to indicate that MCM-22 probably has two distinct pore systems containing 10- and 12-member rings, which is in accordance with our recently published results of catalytic tests. Quantitative results on Brønsted and Lewis acidity are reported from the i.r. study of pyridine adsorption and from t.p.d. of NH₃. The Brønsted sites are strongly acidic and accessible for pyridine. MCM-22 is very sensitive to the calcination conditions, being more dealuminated on heating in air than in a vacuum or N₂. The dealumination occurs even during grinding in a mortar with a concomitant decrease in the acidity of the final sample.     

Superior Energy Storage Capability and Stability in Lead-Free Relaxors for Dielectric Capacitors Utilizing Nanoscale Polarization Heterogeneous Regions

The development of high-performance lead-free dielectric ceramic capacitors is essential in the field of advanced electronics and electrical power systems. A huge challenge, however, is how to simultaneously realize large recoverable energy density (W_rec), ultrahigh efficiency (η), and satisfactory temperature stability to effectuate next-generation high/pulsed power capacitors applications. Here, a strategy of utilizing nanoscale polarization heterogeneous regions is demonstrated for high-performance dielectric capacitors, showing comprehensive properties of large W_rec (≈6.39 J cm⁻³) and ultrahigh η (≈94.4%) at 700 kV cm⁻¹ accompanied by excellent thermal endurance (20–160 °C), frequency stability (5–200 Hz), cycling reliability (1–105 cycles) at 500 kV cm⁻¹, and superior charging-discharging performance (discharge rate t_0.9 ≈ 28.4 ns, power density PD ≈161.3 MW cm⁻³). The observations reveal that constructing the polarization heterogeneous regions in a linear dielectric to form novel relaxor ferroelectrics produces favorable microstructural characters, including extremely small polar nanoregions with high dynamics and multiphase coexistence and stable local structure symmetry, which enables large breakdown strength and ultralow polarization switching hysteresis, hence synergistically contributing to high-efficient capacitive energy storage. This study thus opens up a novel strategy to design lead-free dielectrics with comprehensive high-efficient energy storage performance for advanced pulsed power capacitors applications.     

Matching CP@NCOH/NF Cathode and GH/FNP/NF Anode for High-Performance Asymmetric Supercapacitor

It is extremely crucial to design and match high-quality cathode and anode for achieving high-performance asymmetric supercapacitors (ASCs). Herein, Co₃(PO₄)₂@NiCo-LDH/Ni foam (CP@NCOH/NF) cathode with hierarchical morphology and graphene hydrogel/Fe–Ni phosphide/Ni foam (GH/FNP/NF) anode with the robust and porous structure are elaborately designed and prepared, respectively. Owing to their unique and profitable structures, both CP@NCOH/NF and GH/FNP/NF electrodes yield the superior capacity (10760 and 2236 mC cm⁻² at 2 mA cm⁻², respectively), good rate capability (63% retention at 200 mA cm⁻² and 52% retention at 50 mA cm⁻², respectively), and excellent cycling stability (72% and 74% retention after 10 000 cycles, respectively). Benefiting from their matchable electrochemical performances, the configured solid-state CP@NCOH/NF//GH/FNP/NF ASC outputs both competitive energy density (80.2 Wh kg⁻¹/4.1 mWh cm⁻³) and power density (14563 W kg⁻¹/750 mW cm⁻³), companied by remarkable cyclability (71% retention after 10 000 cycles), manifesting its great promise for large-scale integrated energy-storage system.     

Electronic absorption spectrum of Mn2+ ions doped in ammonium perchlorate single crystal

The absorption spectrum of Mn²⁺ ions doped in ammonium perchlorate has been studied. The observed bands are assigned as transitions from the ⁶A_lg(S) ground state to various excited quartet states of Mn²⁺ ion in octahedral symmetry. The observed band positions are fitted with four parameters B, C, Dq and α and the best fit is obtained with B = 800 cm⁻¹, C = 3150 cm⁻¹, Dq = 800 cm⁻¹ and α = 76 cm⁻¹.     

Oxide impurity absorptions in Ge-Se-Te glass fibres

Oxide impurity absorptions in Ge-Se-Te glass fibres and the cause of the absorption loss around 943 cm^–1, the frequency of the CO² laser, have been investigated. The oxygen in the glass bounds preferentially to germanium and causes the absorptions due to Ge-O bond vibrations at 765 cm^–1 (band I) and 1230cm^–1 (band II). The excess absorptions due to these bands were determined as 0.228cm^–1/P.p.m. wt O₂ for band-I and 0.006cm^–1 /p.p.m. wt O₂ for band II. The loss of the fibre at 943cm^–1 increased with the oxygen content. It was, however, revealed from the deconvolution of the IR spectra into the independent absorption components that the absorption tails of band I and band II did not affect the loss at 943 cm^–1. The content of the impurities except oxygen analysed by a mass spectroscopy was too low to affect the loss at 943 cm^–1.     

Structural characterization of β-SiC nanowires synthesized by direct heating method

Crystal structure of β-SiC nanowires was investigated using Raman spectroscopy, FT-IR, XRD, transmission electron microscopy and selected area electron diffraction. Cubic β-SiC nanowires were synthesized by heating NiO catalyzed Si substrates with WO₃ and graphite mixed powders in the growth temperature of 1000–1100 °C. HRTEM image showed atomic arrangements of the grown SiC nanowires with a main growth direction of [111]. Raman spectra showed two characteristic peaks at 796 cm^− 1 and 968 cm^− 1, which are corresponding to transversal optic mode and longitudinal optic mode of β-SiC, respectively. Also, FT-IR absorption spectroscopy showed a SiC characteristic absorption band at ∼792 cm^− 1.     

Hydrogen-Doping-Induced Metal-Like Ultrahigh Free-Carrier Concentration in Metal-Oxide Material for Giant and Tunable Plasmon Resonance

The practical utilization of plasmon-based technology relies on the ability to find high-performance plasmonic materials other than noble metals. A key scientific challenge is to significantly increase the intrinsically low concentration of free carriers in metal-oxide materials. Here, a novel electron–proton co-doping strategy is developed to achieve uniform hydrogen doping in metal-oxide MoO₃ at mild conditions, which creates a metal-like ultrahigh free-carrier concentration approaching that of noble metals (10²¹ cm⁻³ in H_1.68MoO₃ versus 10²² cm⁻³ in Au/Ag). This bestows giant and tunable plasmonic resonances in the visible region to this originally semiconductive material. Using ultrafast spectroscopy characterizations and first-principle simulations, the formation of a quasi-metallic energy band structure that leads to long-lived and strong plasmonic field is revealed. As verified by the surface-enhanced Raman spectra (SERS) of rhodamine 6G molecules on H_xMoO₃, the SERS enhancement factor reaches as high as 1.1 × 10⁷ with a detection limit at concentration as low as 1 × 10⁻⁹ mol L⁻¹, representing the best among the hitherto reported non-metal systems. The findings not only provide a set of metal-like semiconductor materials with merits of low cost, tunable electronic structure, and plasmonic resonance, but also a general strategy to induce tunable ultrahigh free-carrier concentration in non-metal systems.     

Electronic-Grade High-Quality Perovskite Single Crystals by a Steady Self-Supply Solution Growth for High-Performance X-ray Detectors

High-quality perovskite single crystals with large size are highly desirable for the fundamental research and high energy detection application. Here, a simple and convenient solution method, featuring continuous-mass transport process (CMTP) by a steady self-supply way, is shown to keep the growth of semiconductor single crystals continuously stable at a constant growth rate until an expected crystal size is achieved. A significantly reduced full width at half-maximum (36 arcsec) of the (400) plane from the X-ray rocking curve indicates a low angular dislocation of 6.8 × 10⁶ cm⁻² and hence a higher crystalline quality for the CH₃NH₃PbI₃(MAPbI₃) single crystals grown by CMTP as compared to the conventional inverse temperature crystallization (ITC) method. Furthermore, the CMTP-based single crystals have lower trap density, reduced by nearly 200% to 4.5 × 10⁹ cm⁻³, higher mobility increased by 187% to 150.2 cm² V⁻¹ s⁻¹, and higher mobility–lifetime product increased by around 450% to 1.6 × 10⁻³ cm² V⁻¹, as compared with the ITC-grown reference sample. The high performance of the CMTP-based MAPbI₃ X-ray detector is comparable to that of a traditional high-quality CdZnTe device, indicating the CMTP method as being a cost-efficient strategy for high-quality electronic-grade semiconductor single crystals.     

Indium selenide film formation by the double-source evaporation of indium and selenium

Films of γ-In₂Se₃ are easily obtained by the evaporation of indium and selenium with the supply ratio R = [Se]/[In] above 1.7 and the substrate temperature T_s above 170°C. InSe films are obtained when R ≈ 1.2 and T_s > 100°C. The electrical conductivities of γ-In₂Se₃ and InSe films are about 10⁻¹⁰−10⁻⁷ and 10⁻⁶ S cm⁻¹ respectively. The band gap of γ-In₂Se₃ is estimated to be about 2 eV in this study.The mechanism of film formation is also discussed.     

Study on optical weak absorption of borate crystals

Borate crystal is an important type of nonlinear optical crystals used in frequency conversion in all-solid-state lasers. Especially, LiB₃O₅ (LBO), CsB₃O₅ (CBO) and CsLiB₆O₁₀ (CLBO) are the most advanced. Although these borate crystals are all constructed by the same anionic group-(B₃O₇)⁵⁻, they show different nonlinear optical properties. In this study, bulk weak absorption values of three borate crystals have been studied at 1064 nm by a photothermal common-path interferometer. The bulk weak absorption values of them along [1 0 0], [0 1 0] and [0 0 1] directions were obtained, respectively, to be approximately 17.5 ppm cm⁻¹, 15 ppm cm⁻¹ and 20 ppm cm⁻¹ (LBO); 80 ppm cm⁻¹, 100 ppm cm⁻¹ and 40 ppm cm⁻¹ (CBO); 600 ppm cm⁻¹, 600 ppm cm⁻¹ and 150 ppm cm⁻¹ (CLBO) at 1064 nm. The results showed an obvious discrepancy of the values of these crystals along three axis directions. A correlation between the bulk weak absorption property and crystal intrinsic structure was then discussed. It is found that the bulk weak absorption values strongly depend on the interstitial area surrounded by the B–O frames. The interstitial area is larger, the bulk weak absorption value is higher.     

Identification of thaumasite in concrete by Raman chemical imaging

Identification of thaumasite (CaSiO₃·CaO₃·CaSO₄·15H₂O) in concrete undergoing external sulfate attack by X-ray powder diffraction or by microscopic techniques is difficult due to its crystallographic and morphological similarity with ettringite. Widefield Raman chemical imaging via liquid crystal tunable filter (LCTF) technology has been used in a preliminary study to determine the presence of thaumasite in association with ettringite (3CaO·Al₂O₃·3CaSO₄·32H₂O) and gypsum (CaSO₄·2H₂O). Raman chemical imaging combines Raman spectroscopy with optical microscopy and digital imaging to provide images with molecular-based contrast. Thaumasite has three major peaks at 658, 990, 1076 cm⁻¹ and three minor peaks at 417, 453, 479 cm⁻¹. Ettringite has major peaks at 990, 1088 cm⁻¹. Gypsum has a major peak at 1009 cm⁻¹ and minor peaks at 417, 496, 621, 673, 1137 cm⁻¹. When these minerals are presented together, Raman chemical imaging provides an excellent way to determine their molecular composition and spatial distribution within the sample.     

Improving the Oxygen Evolution Activity of Layered Double-Hydroxide via Erbium-Induced Electronic Engineering

Layered double-hydroxide (LDH) has been considered an important class of electrocatalysts for the oxygen evolution reaction (OER), but the adsorption-desorption behaviors of oxygen intermediates on its surface still remain unsatisfactory. Apart from transition-metal doping to solve this electrocatalytic problem of LDH, rare-earth (RE) species have sprung up as emerging dopants owing to their unique 4f valence-electronic configurations. Herein, the Er is chosen as a RE model to improve OER activity of LDH via constructing nickel foam supported Er-doped NiFe-LDH catalyst (Er-NiFe-LDH@NF). The optimal Er-NiFe-LDH@NF exhibits a low overpotential (191 mV at 10 mA cm⁻²), high turnover frequency (0.588 s⁻¹), and low activation energy (36.03 kJ mol⁻¹), which are superior to Er-free sample. Electrochemical in situ Raman spectra reveal the facilitated transition of Ni-OH into Ni-OOH for promoted OER kinetics through the Er doping effect. Theoretical calculations demonstrate that the introduction of Er facilitates the spin crossover of valence electrons by optimizing the d band center of NiFe-LDH, which leads to the G_O-G_HO closer to the optimal activity of the kinetic OER volcano by balancing the bonding strength of *O and *OH. Moreover, the Er-NiFe-LDH@NF presents high practicability in electrochemical water-splitting devices with a low driving potential of and a well-extended driving period.     

Infrared signals correlated with self-interstitial clusters in neutron-irradiated silicon

Using infrared spectroscopy we have investigated the defect spectrum of neutron-irradiated Czochralski–silicon (Cz–Si). The study was focused on three weak signals, mainly on a band at 533 cm^?1, as well as on two other bands at 582 and 592 cm^?1. The band at 533 cm^?1 disappears from the spectra at ~170 °C exhibiting similar thermal stability with the Si-P₆ electron paramagnetic resonance spectrum, previously correlated with a di-interstitial defect. The suggested model for the latter defect, comprising two self-interstitials placed symmetrically a lattice site Si atom, is very similar with that of the allene molecule. This allowed the calculation of the vibrational frequency of the suggested di-interstitial structure giving a value close to the 533 cm^?1, in further support of the above assignment. The band at 582 cm^?1 is stable up to 550 °C. The possible correlation of its origin to large self-interstitial clusters is examined. Also, the origin of the 592 cm^?1 band, which is stable up to 200 °C is discussed, with indications tentatively pointing to a CV pair.     

FeP@C Nanotube Arrays Grown on Carbon Fabric as a Low Potential and Freestanding Anode for High‐Performance Li‐Ion Batteries

An anode of self‐supported FeP@C nanotube arrays on carbon fabric (CF) is successfully fabricated via a facile template‐based deposition and phosphorization route: first, well‐aligned FeOOH nanotube arrays are simply obtained via a solution deposition and in situ etching route with hydrothermally crystallized (Co,Ni)(CO₃)_0.5OH nanowire arrays as the template; subsequently, these uniform FeOOH nanotube arrays are transformed into robust carbon‐coated Fe₃O₄ (Fe₃O₄@C) nanotube arrays via glucose adsorption and annealing treatments; and finally FeP@C nanotube arrays on CF are achieved through the facile phosphorization of the oxide‐based arrays. As an anode for lithium‐ion batteries (LIBs), these FeP@C nanotube arrays exhibit superior rate capability (reversible capacities of 945, 871, 815, 762, 717, and 657 mA h g⁻¹ at 0.1, 0.2, 0.4, 0.8, 1.3, and 2.2 A g⁻¹, respectively, corresponding to area specific capacities of 1.73, 1.59, 1.49, 1.39, 1.31, 1.20 mA h cm⁻² at 0.18, 0.37, 0.732, 1.46, 2.38, and 4.03 mA cm⁻², respectively) and a stable long‐cycling performance (a high specific capacity of 718 mA h g⁻¹ after 670 cycles at 0.5 A g⁻¹, corresponding to an area capacity of 1.31 mA h cm⁻² at 0.92 mA cm⁻²).     

Synthesis and characterization of a chromium silicalite-1

Chromium silicalites have been synthesized and characterized using several spectroscopic techniques. I.r. measurements associated with e.p.r. and solid-state n.m.r. data tend to indicate an isomorphous substitution of Si⁴⁺ by chromium ions in the silicalite framework. An absorption band at 960 cm⁻¹ on the i.r. spectrum, characteristic of the incorporation in the case of titanosilicalites, is observed. Furthermore, i.r. of adsorbed pyridine reveals the existence of pyridinium ions in the material.     

A Cobalt-Free Multi-Phase Nanocomposite as Near-Ideal Cathode of Intermediate-Temperature Solid Oxide Fuel Cells Developed by Smart Self-Assembly

An ideal solid oxide fuel cell (SOFC) cathode should meet multiple requirements, i.e., high activity for oxygen reduction reaction (ORR), good conductivity, favorable stability, and sound thermo-mechanical/chemical compatibility with electrolyte, while it is very challenging to achieve all these requirements based on a single-phase material. Herein, a cost-effective multi-phase nanocomposite, facilely synthesized through smart self-assembly at high temperature, is developed as a near-ideal cathode of intermediate-temperature SOFCs, showing high ORR activity (an area-specific resistance of ≈0.028 Ω cm² and a power output of 1208 mW cm⁻² at 650 °C), affordable conductivity (21.5 S cm⁻¹ at 650 °C), favorable stability (560 h operation in single cell), excellent chemical compatibility with Sm_0.2Ce_0.8O_1.9 electrolyte, and reduced thermal expansion coefficient (≈16.8 × 10⁻⁶ K⁻¹). Such a nanocomposite (Sr_0.9Ce_0.1Fe_0.8Ni_0.2O_3–δ) is composed of a single perovskite main phase (77.2 wt%), a Ruddlesden–Popper (RP) second phase (13.3 wt%), and surface-decorated NiO (5.8 wt%) and CeO₂ (3.7 wt%) minor phases. The RP phase promotes the oxygen bulk diffusion while NiO and CeO₂ nanoparticles facilitate the oxygen surface process and O²⁻ migration from the surface to the main phase, respectively. The strong interaction between four phases in nanodomain creates a synergistic effect, leading to the superior ORR activity.