Processing of high-performance Co doped Y2O3 as a single-phase electrolyte for low temperature solid oxide fuel cell (LT-SOFC)

The high-performance single-phase semiconductor materials with higher ionic conductivity have drawn substantial attention in fuel cell applications. Semiconductor materials play a key role to enhance ionic conductivity subsequently promoting low temperature solid oxide fuel cell (LT-SOFC) research. Herein, we proposed a semiconductor Co doped Y₂O₃ (YCO) samples with different molar ratios, which may easily access the high ionic conductivity and electrochemical performances at low operating temperatures. The resulting fabricated fuel cell 10% Co doped Y₂O₃ (YCO-10) device exhibits high ionic conductivity of ∼0.16 S cm⁻¹ and a feasible peak power density of 856 mW cm⁻² along with 1.09 OCV at 530 °C under H₂/air conditions. The electrochemical impedance spectroscopy (EIS) reveals that YCO-10 electrolyte based SOFC device delivers the least ohmic resistance of 0.11–0.16 Ω cm² at 530-450 °C. Electrode polarization resistance of the constructed fuel cell device noticed from 0.59 Ω cm² to 0.28 Ω cm² in H₂/air environment at different elevated temperatures (450 °C to 530 °C). This work suggests that YCO-10 can be a promising alternative electrolyte, owing to its high fuel cell performance and enhanced ionic conductivity for LT-SOFC.     

Reactivity and stability of Zr–doped CeO2 for solar thermochemical H2O splitting in combination with partial oxidation of methane via isothermal cycles

Ceria-based oxides have attracted a lot of attention as an attractive redox material because of their large capacity for storing and releasing oxygen in the solar-driven thermochemical water splitting (STWS) process. Nevertheless, the extremely high temperatures and low oxygen partial pressure required to achieve deep degrees of reduction and large temperature swing in a redox cycle introduce challenges in the practical implementation. These above challenges can be addressed in a unique way by integrating partial oxidation of methane into the reduction step. The STWS can therefore operate isothermally at significantly lower temperatures. In this work, the CeO₂-ZrO₂ solid solutions (Ce_1-xZr_xO₂) are synthesized, characterized, and assessed for thermochemical water splitting in combination with partial oxidation of methane. Up to 160 consecutive redox cycles are also conducted in a bench-scale fixed bed. At an operating temperature of 900 °C, methane successfully promotes the reduction of Ce_1-xZr_xO₂ to produce the synthesis gas with a 2:1H₂/CO ratio and 87.86% selectivity. When compared to CeO₂, the thermodynamic fuel generation capability of CeO₂ with Zr⁴⁺ doping is three times greater in the partial oxidation of methane step and water splitting step. Ce_0.8Zr_0.2O₂ (C8Z2) demonstrates the best redox activity in terms of CO and H₂ production in a redox cycle among the various Zr⁴⁺ doping levels. After 160 consecutive redox cycles, C8Z2 is also very robust, maintaining its redox activity. The C8Z2 composite redox solid solution thus exhibits excellent redox activity and long-term redox stability, potentially making it appropriate for STWS in combination with partial oxidation of methane.     

Designing Gadolinium-doped ceria electrolyte for low temperature electrochemical energy conversion

Reducing the operational temperature of solid oxide fuel cells (SOFC) is vital to improving their durability and lifetime. However, a traditional SOFC suffers from high ohmic and polarization losses at low temperatures, leading to poor performance. Gadolinium-doped ceria is the best ionic conductor for SOFC at lower temperatures. The present work envisages the GDC as an electrolyte for applying low-temperature solid oxide fuel cells (LT-SOFCs). So, in this regard, herein, GDC is synthesized through a wet chemical co-precipitation technique as a functional electrolyte layer fixed between two symmetrical porous electrodes NCAL (Ni_0.8Co_0.15Al_0.05LiO₂). Due to the improved surface properties of the synthesized GDC, particles perform better than commercially available GDC. The synthesized GDC electrolyte shows an impressive fuel cell performance of 569 mW/cm² and a high ionic conductivity of 0.1 S/cm at a shallow temperature of 450 °C. Moreover, the fuel cell device utilizing the synthesized GDC remained stable for 150 h of operation at a high current density of 110 mA/cm² at 450 °C. The high conduction mechanism has been proposed in detail. The results show that excellent fuel cell performance, high ionic conductivity, and better stability can be achieved at exceptionally low enough temperatures. Also, the proposed work suggests that new electrolytes can be designed for developing advanced low-temperature fuel cell technology.     

基于有限元的基坑明挖施工中支护结构变形监测方法

针对变形监测结果精度较低,与实际值偏差较大的问题,提出基于有限元的基坑明挖施工中支护结构变形监测方法.以天河机场南北联通隧道基坑明挖工程为例,利用有限元法数值模拟复合土钉墙和下部锚拉桩墙组合体系,依据数值计算结果设计组合支护体系,并针对不同监测对象设置相应的监测方案,监测基坑明挖施工中支护结构水平位移、竖向位移、侧向位...     

Flower-like MOF-derived Co–N-doped carbon composite with remarkable activity and durability for electrochemical hydrogen evolution reaction

Electrochemical hydrogen evolution reaction (HER) is one of the most economical, sustainable, and attractive methods to produce hydrogen. Contemporarily, it is still a challenge to develop low-cost catalysts with high activity and durability for HER. Herein, we report a simple strategy to develop a Co–N-doped carbon electrocatalyst derived from a new cobalt metal-organic framework (MOF). The new flower-like 2D→3D MOF {[Co(BIPA)(5-OH-bdc)](DMF)}_n (1) was constructed based on bis(4-(1H-imidazol-1-yl)phenyl)amine (BIPA) and 5-hydroxyisophthalic acid (5-OH-H₂bdc). After that, the Co–N-doped carbon composite Co-MOF-800 was prepared via calcination of MOF 1. Interestingly, Co-MOF-800 exhibited excellent electrocatalytic activity and durability for HER. The onset potential (0.12 V) and E_j=10 value (0.193 V) of the Co-MOF-800 electrode were comparable to that of the most active non-precious metal HER electrocatalysts derived from other MOFs. The HER performance of Co-MOF-800 was stable without degradation even after long-term cycling.     

Boosting hydrogen evolution activity and durability of Pd–Ni–P nanocatalyst via crystalline degree and surface chemical state modulations

Developing efficient, durable, and economical electro-catalysts for large-scale commercialization of hydrogen evolution (HER) is still challenging. Herein, we report for the first time, to the best of our knowledge, a Pd-based ternary metal phosphide as an active and stable HER catalyst. The face-centered-cubic Pd–Ni–P nanoparticles (NPs) annealed at 400 °C show the best HER activity with a low overpotential of 32 mV to realize a current density of 10 mA cm⁻² and a high mass activity of 1.23 mA μg⁻¹_Pd, superior to Pd NPs, Pd–P NPs, Pd–Ni NPs, and Pd–Ni–P NPs annealed under different temperatures. Moreover, this catalyst is also highly stable during 20 h of continuous electrolysis. Notably, the easily fabricated Pd–Ni–P NPs are among the most active Pd-based HER catalysts. This work indicates that Pd-based metal phosphides could be potentially applied as a type of practical HER catalyst and might inform the fabrication of analogous materials for hydrogen-related applications.     

轨道角动量模传输的圆环形光子晶体光纤

设计了一种新型轨道角动量模传输的圆环形光子晶体光纤,包层为排列有序的矩形空气孔围绕纤芯呈圆形排列,纤芯为大的空气孔,中间环形高折射率区为光子轨道角动量传输区。利用基于有限元法的COMSOL Multiphysics软件进行仿真分析,对光子轨道角动量模式在光纤中的传输特性进行了详细讨论。结果表明,该结构可实现1.2~2.0 m波段50个轨道角动量模式的有效分离和稳定传输,简并模式的有效折射率差大于10-4,保证了每个模式的稳定传输;限制损耗仅为10-9 dBm-1,非线性系数低至0.833 km-1W-1。该光纤可以应用于模分复用系统,将大大提高通信系统容量和频谱效率。     

Structural,optical, and photocatalytic properties of the spray deposited nanoporous CdS thin films; influence of copper doping,annealing, and deposition parameters

Nanoporous thin films of Cd_1−xCu_xS (0≤x≤0.06) were grown on a heated glass substrate employing a home-made spray pyrolysis technique. The influences of [Cu]/[Cd] and the annealing in the range 300–500 °C on the structural and morphological properties of the films were investigated by X-ray diffraction (XRD), Fourier transformation infrared spectroscopy (FTIR), field emission scanning electron microscope (FE-SEM) and atomic force microscopy (AFM). The influences of Cu doping ratio, solution flow rate, and the deposition time on the optical properties and photocatalytic activity of these films are also reported. The films are of polycrystalline nature and hexagonal structure. Increasing the Cu doping ratio and annealing temperature improve the (1 0 1) preferential orientation. The crystallite size is ranged from 23.82 to 32.11 nm. XRD and FTIR reveal the formation of CdO in the 6% Cu-doped CdS film annealed at 400 °C and in all films annealed at 500 °C. The pure CdS film is of a porous structure and the close-packing and porosity of the films increase with increasing Cu%. Also, the pore diameter can be controlled from 50 to 15 nm with the increase of Cu content. The films showed transmittance below 70%. The optical band gap of the films is decreased from 2.43 to 1.82 eV with increasing Cu% and flow rate/deposition time. Additionally, the refractive indices and dispersion parameters of the films are also affected by the deposition conditions. Cu doping enhanced the films' photostability as well as the photocatalytic removal of methylene blue (MB).     

On the validity of the formation of crystalline carbon nitrides,C3N4

X-ray powder diffraction patterns were simulated for five structures proposed for C₃N₄ — i.e., β-, α-, defect zincblend-type and cubic C₃N₄ — with lattice constants and structure parameters reported in the literature. The comparison of experimental X-ray and electron diffraction patterns assigned to crystalline carbon nitrides with simulated ones has led us to conclude that no work has yet presented unambiguous evidence for the crystallization of carbon nitrides with the proposed structures. Disordered polytypic diamond has been proposed as the most probable candidate for part of the products which have hitherto been regarded as C₃N₄.