Integrating coral-like morphology into cyano-containing carbon nitride towards efficient photocatalytic H2 evolution and Cr(Ⅵ) reduction

The incomplete polymerization of graphite carbon nitride (g-C₃N₄) due to the kinetic problems resulted in its high recombination rate of photo-generated electron-hole pairs. Hence, cyano-containing carbon nitride with coral-like morphology (CCCN) was prepared by the molten salt method with heptazine-based melem as precursor, which presented excellent separation rate of photo-generated electron-hole pairs. SEM exhibited that CCCN owned coral-like morphology which exposed ample active sites and enhanced the capture ability of visible light while FT-IR and XPS demonstrated that cyano groups appearing in coral-like carbon nitride enhanced the separation rate of photo-induced charge carriers. The synergistic effect of coral-like morphology and cyano groups endowed CCCN-15% with superior performance of both the photocatalytic H₂ evolution (4207 μmol h^?1 g^?1) and Cr (Ⅵ) reduction (k = 0.059 min^?1), approximately 16.8 and 6.0 times that of g-C₃N₄, which was comparable among the similar materials. Density functional theory calculation (DFT) revealed that cyano groups decreased the bandgap and strengthened the activation degree of reaction substrate, which enhanced the thermodynamic driving force and the interaction between catalyst and substrate. This work provided a potential strategy for both the renewable energy generation and environmental restoration.     

Rapid preparation of Palygorskite/Al2O3 composite aerogels with superhydrophobicity,high-temperature thermal insulation and improved mechanical properties

Al₂O₃ aerogels are widely employed in heat insulation and flame retardancy because of their unique combination of low thermal conductivity and exceptional high-temperature stability. However, the mechanical properties of Al₂O₃ aerogel are poor, and the preparation time is considerably long. In this study, we present a simple and scalable approach to construct monolithic Pal/Al₂O₃ composite aerogels using solvothermal treatment instead of traditional solvent replacement, which remarkably shortened the preparation time. Subsequently, to obtain stable superhydrophobicity (θ > 152°), the Pal/Al₂O₃ aerogel was modified by gas-phase modification method. The obtained Pal/Al₂O₃ composite aerogels demonstrate the integrated properties of low density (0.078–0.106 g/cm³), low thermal conductivity (1000 °C, 0.143 W/(m·K)), good mechanical properties (Young's modulus, 1.6 MPa), and good heat resistance. The monolithic Pal/Al₂O₃ composite aerogels with improved mechanical performance and improved thermal stability can show great potential in the field of thermal insulation.     

Facile synthesis of black phosphorus directly grown on carbon paper as an efficient OER Electrocatalyst: Role of Interfacial charge transfer and induced local charge distribution

Black phosphorus (BP), as a new 2D material, is normally synthesized by a high-pressure and high-temperature (HPHT) method from white and red phosphorus, which severely hinders the further development of BP for any potential applications and leads to search for other potential applications of BP with big challenge. Herein, we develop a facile and efficient Thermal-Vaporization-Transformation (TVT) approach to prepare a highly active BP directly grown on carbon paper as the electrode for Oxygen evolution reaction (OER), showing a low onset potential of 1.45 V versus RHE. Simultaneously, the current density of BP-CP illustrates the excellent electro-catalysis stability only decreases by 3.4% after continuous operation for 10000 s. Meanwhile, the density functional theory (DFT) calculations further illustrates the P-doped carbon layer in the upper side of BP layer is actually responsible for its enhanced OER property, and the adjacent carbon atoms of the embedded P atoms are actually the active sites due to the induced local change distribution by intramolecular change transfer. Considering the facile, but efficient and scalable, TVT approach can directly synthesize BP-CP with excellent OER performance, which is promising for BP electrocatalysts used for OER in metal-air batteries, fuel cells, water-splitting devices, even other key renewable energy.     

High performance asymmetric supercapacitor based on 3D microsphere-like 1T-MoS2 with high 1T phase content

1T phase molybdenum disulfide (1T-MoS₂) has aroused extensive concern in energy storage devices such as supercapacitors due to its large interlayer spacing, high conductivity and good hydrophilicity. However, it is struggle to synthesize 1T-MoS₂ with stable 1T phase with high content. Herein, Ammonium ion intercalation molybdenum disulfide (A-MoS₂) with high 1T content and stable 3D microsphere structure was successfully synthesized using a facile hydrothermal method. We explained the feasibility of ammonium ion (NH₄⁺) intercalation through density functional theory (DFT) calculations and proved the successful intercalation of NH₄⁺ by XRD and XPS. Through XPS fitting, the 1T phase content is calculated as high as 83.1%. The as-prepared A-MoS₂ presents a stable 3D microsphere structure with the interlayer spacing expanded to 0.93 nm, which provides a wide ion diffusion channel that allows ions to pass through quickly. Moreover, the high 1T content increases the hydrophilicity of MoS₂, thereby improving the wettability of the electrode, which contributes to the interaction between the electrolyte and electrode. In 1 M Na₂SO₄, A-MoS₂ electrode material displays high specific capacitance of 228 F g^?1 at 5 mV s^?1 and retains 127 F g^?1 at 80 mV s^?1, which proves the good rate capability. Furthermore, the assembled α-MnO₂//A-MoS₂ asymmetric supercapacitor (ASC) displayed a wide operating voltage of 2.1 V. The assembled ASC displays a high energy density of 35.8 Wh?kg^?1 at a power density of 525.0 W kg^?1, which indicates excellent energy storage performance.     

In Situ Anchoring Ultra Small Au Nanoparticles by Conformal Coating of Carbon Layer within the Micro-Environments of Mesoporous Silica for Highly Efficient Catalytic Reduction of 4-nitrophenol

Catalysis Letters - For the noble-metal based catalysts, the metal dispersion and sinter resistance of the metal nanoparticles (NPs) are the most vital factors for their application in series...     

基于钴改性的钙基吸附剂污泥富氢气化

基于钙基吸附剂的污泥蒸汽气化制取富氢合成气是一种高效环保的污泥处理方式。本文采用溶胶-凝胶法制备了Co改性、Al₂O₃为载体的钙基吸附剂。借助热重分析仪测定不同钙基吸附剂在多个碳酸化和煅烧循环中的CO₂吸附能力和循环稳定性，并在固定床上进行污泥蒸汽气化实验。结果显示：煅烧过程中，以Al₂O₃为载体的钙基吸附剂中的Al₂O₃与CaO生成七铝酸十二钙(Ca₁₂Al₁₄O₃₃)，并表现出优异的孔隙结构的和CO₂吸附能力，其中，Co质量分数为10%的吸附剂在30次循环（700℃碳酸化35min，850℃煅烧5min）中碳酸化率稳定在70%左右；提高气化温度及Co的添加量可促进焦油裂解和甲烷重整反应，显著提高了合成气中H₂的浓度和产量及污泥气化的冷煤气效率，有利于富氢气体的制取；在650℃下，相比于纯CaO，添加Co质量分数为15%的吸附剂时，H₂产量提高了102%，H₂体积分数提高到85%。     

Enhanced temperature stable dielectric properties and energy-storage density of BaSnO3-modified (Bi0.5Na0.5)0.94Ba0.06TiO3 lead-free ceramics

A series of (1-x)(Bi_0.5Na_0.5)_0.94Ba_0.06TiO₃-xBaSnO₃ (BNBT-100xBSN, x = 0–20) lead-free ceramics were synthesized using a conventional high-temperature solid-state reaction route. The effects of BaSnO₃ on the dielectric, ferroelectric and energy-storage performance of BNBT-BSN were systematically investigated. Temperature dependent permittivity curves indicated the obviously enhanced relaxor ferroelectric property. The introduction of BaSnO₃ reduced the temperature corresponding to the first dielectric anomaly, which facilitated the dielectric temperature stability. △ε'/ε'_150°C varied no more than 15% within the temperature range of up to 338 °C (45–383 °C) for BNBT-15BSN. A slimed P-E loop was obtained with the remnant polarization of 0.4 μC/cm² for BNBT-15BSN. Moreover, the breakdown field intensity of BNBT-BSN increased effectively from 80 kV/cm to 115 kV/cm. Therefore, an optimum energy-storage performance was obtained in BNBT-15BSN with the energy-storage density of 1.2 J/cm³ whose energy-storage efficiency reached 86.7%. Furthermore, the possible contributions of defect and vacancy to relaxation and conductance mechanism were discussed by studying the impedance and electric modulus. The results above indicated the BNBT-100xBSN be a promising lead-free candidate for energy-storage capacitors.     

Experimental study of hydrogen explosion in repeated pipe congestion – Part 1: Effects of increase in congestion

Experimental studies were conducted with the objective of gaining a better understanding of the potential explosion hazard consequences that could be associated with a high-pressure leak from a hydrogen vehicle refuelling system. The first part of the study, described in this paper, was a series of experiments designed to establish hydrogen–air explosion overpressures in a well-defined and well understood 3 m × 3 m x 2 m (high) repeated pipe congestion. The results of the experiments are discussed in terms of the conditions leading to the greatest overpressures. It is concluded from the study that stoichiometric ratio in the range of 1.2–1.3 gives highest overpressure. Moreover, it was observed that increasing the congestion from 4-gate to 9-gate congestion leads to significant increase in the overpressure. In addition, it was concluded that, explosion in a hydrogen-air mixture is significantly more severe than the explosion in an ethane-air, methane-air or propane-air mixtures. This is attributed to higher laminar flame speed of hydrogen-air mixtures.     

分级加载电压下考虑有效电势变化的软黏土电渗固结理论

分级加载电压技术能够有效延长电渗处理的时间,改善地基的处理效果并能有效降低能耗。在利用分级加载电压技术开展电渗试验时,随着土体的排水固结,土体各点的电势会发生明显的变化,这与现有的电渗固结理论假设土体各点电势保持不变有所差异。利用自主设计的电渗试验仪器开展了分级加载电压下的电渗室内试验,分析了电渗过程中土体有效电势变化的规律。基于该规律并结合Esrig固结理论建立了在阳极处不排水、阴极处排水条件下考虑土体有效电势变化的电渗固结理论,得到了分级加载电压条件下考虑土体有效电势变化的超静孔隙水压力和平均固结度的解析表达式。研究表明,在电压分级加载过程中,土体有效电势变化规律表现为随时间先基本保持不变,后呈抛物线状先增后减。通过试验案例验证了考虑土体有效电势变化所求得解析解的合理性,且该数值计算结果相较于Esrig数值计算结果,前者更加接近实测值,该固结方程的建立为后续分级加载电压技术的推广应用提供了理论依据,也为实际工程提供了参考。     

Strain properties of (1-x)Bi0.5Na0.4K0.1TiO3-xBi(Mg2/3Ta1/3)O3 electroceramics

A ternary solid solution of Bi_0.5Na_0.5TiO₃–Bi_0.5K_0.5TiO₃–Bi(Mg_2/3Ta_1/3)O₃ (BNKT-xBMT) lead-free electroceramics was synthesized by a solid-state reactive sintering technique. The electrostrain, dielectric, and ferroelectric properties as well as the impedance characteristics and the microstructure were systematically assessed. With the increase of BMT, the BNKT-xBMT ceramics gradually transformed from non-ergodic relaxor phase to ergodic relaxor phase, manifested as the ferroelectric-to-relaxor temperature (T_F-R) shifts towards below room temperature. Additionally, the ferroelectric hysteresis curves became pinched, and the strain curve changed from butterfly-shaped into sprout-shaped. At the ergodic relaxor composition of x = 0.04, a large electrostrain value (S = 0.4%; under an electric field of 60 kV/cm, d₃₃* = 632 pm/V) was achieved, which is mainly attributed to the electric-field-induced transition from the ergodic relaxor phase to the ferroelectric phase.