Table of Content

15 April 2024, Volume 53 Issue 4

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Research Letter

Growth and Device Fabrication of Mid to Far-Infrared Cr²⁺/Fe²⁺∶CdSe Crystals

HUANG Changbao, HU Qianqian, ZHU Zhicheng, LI Ya, MAO Changyu, XU Junjie, WU Haixin, NI Youbao

2024, 53(4):  551-553. 

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In this study, the Cr²⁺∶CdSe and Fe²⁺∶CdSe crystals were successfully grown by the Mo-crucible sealed Bridgman method using a vacuum single-crystal furnace with two zones developed by ourselves, and the crystal size reaches ϕ51 mm×110 mm. Cr²⁺∶CdSe and Fe²⁺∶CdSe crystals demonstrate obvious absorption in the bands of 1 400~2 400 nm and 2 500~5 200 nm, respectively. The transmittances of Cr²⁺/Fe²⁺doped CdSe crystals are close to the transmittance limit of CdSe crystal (~70%) in the 7~15 μm band, and the converted absorption coefficient is about 0.005 cm^-1. The Cr²⁺/Fe²⁺∶CdSe crystals grown by the Mo-crucible sealed Bridgman method have the advantages of the controllable doping concentration of transition metal ions, uniform doping and high crystal quality. The Cr²⁺/Fe²⁺∶CdSe crystals could be used as both mid-infrared laser crystal and far-infrared nonlinear optical crystal material.

Reviews

Research Progress for Lead Halide Perovskite Direct Radiation Detector Based on the Solution Method

QIN Feng, WU Jinjie, DENG Ningqin, JIAO Zhiwei, ZHU Weifeng, TANG Xianqiang, ZHAO Rui

2024, 53(4):  554-571. 

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X-ray and γ-ray detection have been extensively studied and applied in medical imaging, security inspection, homeland security, non-destructive testing and other various fields. Perovskite materials have become excellent candidats for radiation detector devices due to their high radiation absorption coefficient, high carrier mobility-lifetime product and defect tolerance. The solution method offers significant advantages in the preparation of perovskite materials. It is a cost-effective approach that can be carried out at low temperatures or under ambient conditions. Additionally, it is also easier to implement for industrial production. This method plays a crucial role in optimizing the material system and achieving the preparation of high quality and large area crystal materials in the future. This paper analyzes the effects of crystal growth and material composition on radiation detection performance, focusing on the solution preparation of perovskite materials. The study aims to improve radiation detection performance by optimizing crystal growth quality and device structure design. Additionally, it also summarises the challenges faced by perovskite materials in the field of radiation detection and suggests future research directions. The results of this study are expected to serve as a reference for the industrialization of perovskite materials in the field of radiation detection.

Research Progress on Preparation of Organic-Inorganic Hybrid Lead Halide Perovskite Single-Crystalline Thin-Films by Solution-Processed Space-Confined Method and Their Device Applications

ZHANG Qingwen, SHAN Dongming, ZHANG Hu, DING Ran

2024, 53(4):  572-584. 

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In recent years, organic-inorganic hybrid lead halide perovskite materials have attracted much attention in the world because of their excellent photoelectric properties, and have been successfully applied in many fields such as solar photovoltaic, photoelectric detection, electroluminescence and so on. At present, most of the device research focuses on perovskite polycrystalline materials, but perovskite single crystal materials have excellent properties such as lower defect state density, higher carrier mobility, longer carrier recombination lifetime, wider light absorption range and higher stability, which can effectively reduce the scattering loss during carrier transport and non-radiative recombination at the grain boundary, and inhibit the hysteresis effect caused by ion migration. Using perovskite single crystal thin film as the active layer of the device is expected to produce more efficient and stable perovskite photoelectric devices. At present, many preparation methods of perovskite single crystal films have been reported, mainly including solution-processed space-confined method, chemical vapor deposition method, top-down processing method, etc. Among them, solution-processed space-confined method is the most widely developed and applied. This paper focuses on the preparation of high-quality perovskite single crystal thin films by solution-processed space-confined method, and the research progress of perovskite single crystal thin films in photodetectors, solar cells, field effect transistors, light-emitting diodes and other related devices, and prospects the future development trend of perovskite single crystal thin films and photoelectric devices.

Research Progress on Material Removal Non-Uniformity in Silicon Carbide Chemical Mechanical Polishing

SUN Xinghan, LI Jihu, ZHANG Wei, ZENG Qunfeng, ZHANG Junfeng

2024, 53(4):  585-599. 

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Chemical mechanical polishing (CMP) has become a critical process step in semiconductor manufacturing. This technique is a commonly used and effective method for achieving ultra-precision processing of silicon carbide wafers, playing a key role in the fabrication of semiconductor devices. CMP is employed to process the wafer surface, resulting in high material removal rates, excellent surface quality, and superior surface planarity of the chips. However, in the CMP of silicon carbide (SiC) wafers, the non-uniformity of material removal on the chip surface has been a challenging issue. Reducing the non-uniformity of material removal is essential for ensuring the high performance and stability of semiconductor devices. This article introduces the properties and applications of silicon carbide, along with the CMP process. It investigates the material removal mechanisms of different CMP techniques for silicon carbide, explores the development status of various CMP technologies, and evaluates the performance and pros and cons of different CMP techniques. The article provides an overview of the factors influencing material removal non-uniformity in CMP of silicon carbide wafers, including factors such as polishing pressure, polishing slurry (abrasives), and rotation speed. Finally, the article provides prospects for future research on material removal non-uniformity in silicon carbide CMP.

Research Progress on the Preparation Method and Application of Molybdenum Disulfide Nanomaterials

ZHANG Jiahao, WANG Dexiu, LI Yuqi, XU Ying, LIANG Shiming, SONG Xuesheng

2024, 53(4):  600-619. 

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This paper delves into the synthesis strategies of molybdenum disulfide (MoS₂) nanomaterials and their prospective applications in the fields of energy conversion and storage. Through a comprehensive analysis of various synthesis methods, including solvothermal and sol-gel processes, the specific impacts of these methods on the morphology and properties of MoS₂ nanostructures are revealed. The study indicates that MoS₂ nanomaterials with optimized electronic properties and surface activity can be fabricated by precisely controlling the synthesis conditions. These materials demonstrate exceptional performance in applications such as lithium-ion batteries and photodetectors, especially in enhancing battery charge-discharge cycle stability and improving photoelectric conversion efficiency. The paper further discusses the challenges faced in the development of MoS₂ applications, particularly in terms of the scalability of material synthesis and consistency of performance. Lastly, the article presents a vision for future research directions, emphasizing the potential to broaden the application of MoS₂ in high-performance energy devices through innovative synthesis strategies and material structure optimization.

Research Articles

Growth and Optical Properties of Yb∶Ca₃(NbGa)₅O₁₂ Crystals by Bridgman Method

ZHAO Tao, AI Lei, LIANG Tuanjie, QIAN Huiyu, SUN Zhigang, PAN Jianguo

2024, 53(4):  620-626. 

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Ytterbium ion doped calcium niobium gallium garnet crystal (Yb∶Ca₃(NbGa)₅O₁₂) was successfully grown by Bridgman method. The structure of the crystal was analyzed by XRD. The crystal is cubic crystal system, and the unit cell parameter a=b=c=12.471 Å. The crystal was tested by Raman spectroscopy, transmission spectroscopy, absorption and emission spectroscopy, and fluorescence lifetime. The absorption cross section, emission cross section, and gain cross section of the crystal were calculated. The effects of annealing in air on the absorption spectrum, emission spectrum and fluorescence lifetime of the crystal were studied. The absorption cross section at 935 nm before annealing is 1.82×10^-20 cm², and it decreases to 1.40×10^-20 cm² after annealing. The emission cross section at 1 031 nm before annealing is 0.56×10^-20 cm², and it decreases to 0.40×10^-20 cm² after annealing. The fluorescence decay time before annealing is 1.42 ms, and it is 1.32 ms after annealing. The results demonstrate that the annealing of Yb∶Ca₃(NbGa)₅O₁₂ single crystal in air will adversely affect the laser performance of the crystal.

Growth and Luminescence Properties of Cs₄EuI₆∶Sm Near-Infrared Scintillation Crystals

YANG Jianghao, HUANG Xinshuai, LAN Chenhui, WEI Qinhua, QIN Laishun

2024, 53(4):  627-633. 

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With the rapid development of silicon-based light detectors with high detection efficiency and long-wavelength sensitivity, the development of near-infrared scintillation crystals has become a hotspot. Especially, the Sm²⁺ doped europium-based halide crystals exhibit excellent near-infrared luminescence properties. In this paper, Cs₄EuI₆∶Sm near-infrared scintillation crystals with a size of cm-level were successfully prepared by Bridgman method. The composition and structure were discussed by XRD, XPS and ICP-OES methods, indicating that the Sm²⁺ was introduced and has no obvious effect on the crystal structure of the matrix. Under ultraviolet and X-ray excitation, the crystal has two luminescence centers (Eu²⁺ and Sm²⁺), and the emission peaks are located at 450 and 840 nm, respectively, corresponding to the 5d→4f luminescence of Eu²⁺ and Sm²⁺. The decay time of Eu²⁺ and Sm²⁺ is at the level of microsecond under ultraviolet excitation. The results show that the emission wavelength gradually varies from blue to near infrared as Sm²⁺ doping concentration increased. The effects of Sm²⁺ concentration on the luminescence properties, Eu²⁺-Sm²⁺ energy transfer and decay time of the crystals were also studied, which means that the luminescence properties can be tuned by adjusting the Sm²⁺ doping concenstration.

Study on Bonding Technology of Silicon-Based Lithium Tantalate Heterogeneous Wafers

CHEN Zheming, DING Yuchong, ZOU Shaohong, LONG Yong, SHI Zibin, MA Jinyi

2024, 53(4):  634-640. 

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The development of 5G mobile communication imposes requirements of high frequency, miniaturization, and integration on surface acoustic wave devices. Compared with traditional piezoelectric bulk single crystal material, surface acoustic wave filters fabricated with silicon-based piezoelectric single crystal film materials exhibit advantages such as high frequency, low insertion loss, high temperature stability and so on, making silicon-based piezoelectric single crystal film material prime foundation material. Smart-Cut^TM is the universal method for preparing silicon-based piezoelectric single crystal film materials, and bonding process is one of the most essential procedures. Bonding quality determines the quality of piezoelectric single crystal film and ultimately affects the performance of the devices. In this work, high-quality heterogeneous silicon-based LiTaO₃ wafers with the bonding strength up to 1.84 J/m²and bonding area over 99.9% were achieved through optimizing low-temperature direct bonding process, which includes plasma activation, megasonic cleaning, pre-bonding, and thermal treatment.

Relationship Between Temperature Gradient and Interfacial Shape Stability of CZT Crystal Growth

CAO Cong, LIU Jianggao, FAN Yexia, LI Zhenxing, ZHOU Zhenqi, MA Qisi, NIU Jiajia

2024, 53(4):  641-648. 

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CdZnTe crystals are widely used as epitaxial substrates for HgCdTe thin films for infrared detectors and in the fabrication of room temperature nuclear radiation detectors. During crystal growth, the interface shape is closely related to the heat state. Combined with the numerical simulation technique to control the temperature field distribution during CdZnTe crystal growth, the crystal growth procedure of micro-convex solidification interface by vertical Bridgman method and vertical gradient freeze method were designed, and the single crystal rate of CdZnTe crystals was analyzed according to the actual crystal growth experiments. The distribution spectrum of Zn components in the longitudinal section of CdZnTe crystals with equal diameters was obtained by photoluminescence spectroscopy for compositional testing in order to investigate the relationship between the temperature field distribution at the solid-liquid interface and the macroscopic segregation behavior of Zn components. It is found that the temperature gradient distribution on both sides of the solid-liquid interface significantly influences the shape selection and stability of the solidification interface during the crystal growth process, and a larger temperature gradient on the solid-phase side contributes helps to achieve stable crystal growth at the convex interface, thereby increasing the likelihood of growing single crystals.

Upconversion Luminescence and Temperature Sensing Properties of High Thermal Stabilized CaGdAlO₄∶Er³⁺/Yb³⁺ Phosphors

LI Yuqiang, YANG Jian, WANG Shuai, ZHENG Jiyuan, ZHAO Yan, ZHOU Hengwei, LIU Yuxue

2024, 53(4):  649-655. 

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Obtaining non-contact optical temperature sensing materials with good thermal stability and luminescent properties is one of the current research hotspots. In this work, Er³⁺/Yb³⁺ co doped CaGdAlO₄∶Er_x,Yb_0.10(x=0.006, 0.008, 0.010, 0.012, 0.014) single-phase phosphors were prepared by high-temperature solid-state method. For CaGdAlO₄∶Er_x,Yb_0.10 powders with different Er³⁺ doping concentrations, the particle sizes range from 0.6 μm to 4.2 μm. When the samples are under 980 nm laser excitation, there exists two emission bands in the 500~575 nm range and one emission band in the 630~690 nm. The two stronger green emission bands located at 528 and 550 nm, and they could be attributed to ²H_11/2→⁴I_15/2 and ⁴S_3/2→⁴I_15/2 transitions, while the weaker red emission band at 663 nm could be attributed to ⁴F_9/2→⁴I_15/2 transition of Er³⁺. The optimal upconversion luminescence intensity was obtained from CaGdAlO₄∶Er_0.010,Yb_0.10. In the temperature range of 300~573 K, based on fluorescence intensity ratio FIR_528/550 parameters, the absolute sensitivity S_A increases from 44.4×10^-4 K^-1(@300 K) to 52.0×10^-4 K^-1(@445 K), and then decreases to 49.0×10^-4 K^-1(@573 K). The relative sensitivity S_R decreases monotonically from 0.95×10^-2 K^-1(@300 K) to 0.27×10^-2 K^-1(@573 K). Furthermore, the heating-cooling cycling experiment shows that the thermal repeatability of temperature sensing for the phosphor is better than 98%. The results demonstrate that CaGdAlO₄∶Er_0.010,Yb_0.10 phosphors have potential applications in the field of optical temperature sensing.

First Principles Study on the Structure, Mechanics, Electronic and Optical Properties of Ternary Layered Nitride M₂AlN (M=Ti, Zr) under High Pressure

WU Lihai, YU Puliang, ZHONG Min

2024, 53(4):  656-668. 

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This article employed a first-principles calculation method based on density functional theory to optimize the geometric structure of the ternary layered nitride M₂AlN (M=Ti, Zr). The structural, mechanical, electronic and optical properties of the ternary layered nitride M₂AlN (M=Ti, Zr) under high pressure were investigated. The study of structural and mechanical properties reveal that Ti₂AlN exhibits superior compressibility compared to Zr₂AlN. The elastic constants further validate its mechanical stability under high pressure. Ductility and elastic anisotropy enhance under increasing pressure, with Zr₂AlN demonstrating heightened sensitivity to these pressure conditions. Research on electronic properties reveals that both ternary layered nitrides exhibit metallic behavior, and their covalent character strengthen with increasing pressure. Investigations into the optical properties reveal that the polycrystalline nature and static dielectric functions ε₁(0), along with the static refractive index n(0) of Ti₂AlN and Zr₂AlN along various axes, demonstrate relatively low anisotropy in their optical characteristics. Both ternary nitrides exhibit pronounced capabilities for light absorption and reflectivity. Theoretical inquiries in this study clarified the relevant characteristics of the ternary layered nitrides Ti₂AlN and Zr₂AlN under the elevated pressure, establishing a robust theoretical framework for subsequent experimental investigations.

First Principles Study on the Structure and Interface Properties of GaSe/ZnS Heterostructure

BAO Aida, MA Yongqiang, GUO Xin

2024, 53(4):  669-675. 

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In this paper, a new GaSe/ZnS van der Waals heterostructure (vdWH) is devised and subjected to systematic analysis through first principles calculations in terms of its geometric, electronic and transport properties. The stability of GaSe/ZnS vdWH is verified through binding energy, phonon spectrum, and ab initio molecular dynamics (AIMD) simulation. Additionally, detailed calculations of plane average electron density difference and average electrostatic potential in the features of GaSe/ZnS vdWH interface are provided. The results show that GaSe/ZnS vdWH comprises a heterostructure with a direct band gap of 2.19 eV and high carrier mobility. Among them, the electron mobility along the x direction reaches 1 394.63 cm²·V^-1·s^-1, while the electron mobility along the y direction reaches 1 913.18 cm²·V^-1·s^-1, demonstrating excellent performance and potential applications in electronic nano devices.

First-Principles Study on Photogalvanic Effect and Strain Engineering of Monolayer SnS

XU Zhonghui, XU Shengyuan, LIU Chuanchuan, LIU Guogang

2024, 53(4):  676-683. 

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Photodetectors are widely used in various fields, such as industrial manufacturing and military defense. Researchers have recently sought a photodetector that combines high polarization sensitivity and a robust optical response. As an anisotropic semiconductor material, SnS holds potential for photodetection across the visible light spectrum. This study employs first-principles density functional theory (DFT) along with the non-equilibrium Green's function (NEGF) method to theoretically investigate the optoelectronic properties of the SnS monolayer in two device orientations: Armchair and Zigzag. It is found that the maximum photocurrent values between the two orientations are small at zero bias voltage, and stable photocurrent can be obtained by adding bias voltage. We examine the maximum photocurrent variation under linearly polarized light irradiation within a small bias voltage range (0.1 to 1.0 V), found for the maximum photoresponse of monolayer SnS to be large and stable at photon energy of 2.4 and 3.2 eV, and analyze the underlying mechanism of photoresponse, employing energy band and density of state diagrams. Additionally, we have calculated the extinction ratio of the SnS monolayer, confirming its strong polarization sensitivity. Finally, by subjecting the device to biaxial strain, we significantly speculate to enhance its asymmetry, leading to a substantial increase in photocurrent at zero bias. A compressive strain of -6% notably increases the photocurrent. These findings offer valuable theoretical insights for the design of SnS monolayers as photodetectors.

Particle Size Regulation of SiC Quantum Dots Prepared by Corrosion Method and Effect of Size on Optical Properties

KANG Jie, DING Ziyang, WANG Xiaoyan, LI Lianrong, SUN Weiyun, JIAO Can, SONG Yuepeng

2024, 53(4):  684-691. 

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Silicon carbide quantum dots (QDs) were prepared by simple chemical etching method using a mixture of hydrofluoric acid, nitric acid, and analytically pure sulfuric acid as etchants. Ultrasonic cavitation fragmentation was performed on the corrosive mixture, and then it was subjected to high-speed tomographic cutting in a concentration gradient solvent to obtain silicon carbide QDs with excellent optical properties and controllable particle size. The evolution process of microstructure of SiC QDs during corrosion process, the microstructure and emission spectra of SiC QDs were detected and analyzed, and then correlation mechanism at quantum dots size, spectrum, and color was established by emission spectra as a link. The results show that under the conditions of a=1 000 hypergravity coefficient and a centrifugation time of 120 min, the average diameter of QDs at 0, 30, and 60 mm displacement from the liquid surface is about 2, 5, and 7 nm. Under single wavelength excitation, as the diameter of SiC QDs changes from 2→5→7 nm, the relative intensity peak of photoluminescence shows a red shift from 417→435→445 nm, and the luminescence color also show a corresponding change pattern of blue green→green→yellow green; further research had found that the full width at half maximum of the emission spectra of QDs of three sizes show an increase of 81→97→106 nm with increasing liquid depth. Preliminary analysis suggests that it was due to the higher uniformity of particle size distribution of quantum dots near the upper liquid surface compared to those far away from the upper liquid surface after high-speed centrifugal chromatography cutting.

Synthesis, Crystal Structures and Fluorescent Properties of Zn(II) Complexes Based on 4-Hydroxyisophthalic Acid and Nitrogen-Containing Heterocyclic Ligands

LI Bo, WANG Feiyu, SHEN Hong, MAO Fengyin, LI Yonghui

2024, 53(4):  692-700. 

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Under hydrothermal method condition, 4-hydroxyisophthalic acid (H₂HPHA) and Zn(II) ions reacted with 1,2-di(pyridin-4-yl) ethene (dpee) and 4,4-bipyridine (4,4′-bpy) to obtain two coordination polymers [[Zn(HPHA)(dpee)·(DMA)₂]_n (complex 1) and [Zn(HPHA)₂(4,4′-bpy)₂·DMA]_n (complex 2). The crystal structures were determined by single crystal X-ray diffraction method. The results show that complex 1 crystallizes in the monoclinic space group C2 with each asymmetric unit consisting of one Zn(II) ion, one 4-hydroxyisophthalic acid ligand and one 1,2-di(pyridin-4-yl)ethene ligand. Complex 2 crystallizes in the monoclinic space group P12/c1 with each asymmetric unit consisting of two Zn(II) ions, two 4-hydroxyisophthalic acid ligands and two 4,4′-bipyridine ligands. Fluorescence spectrum analysis show that the excitation peak of complex 1 is 251 nm, emission peak is 397 nm. The complex 2 is 415 nm, emission peak is 513 nm. The thermal stability study shows that the complexes are stable at room temperature.

Process of Preparing Aurichalcite by Ammonia Distillation Method

QIU Shiming, YAN Guanjie, LI Chunliu, WANG Shengjie

2024, 53(4):  701-706. 

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In this paper, aurichalcite was synthesized by ammonia distillation method, using basic copper carbonate, basic zinc carbonate and concentrated ammonia as raw materials. The effects of process conditions on the crystal structure of aurichalcite were studied by XRD, TGA, SEM-Mapping and FT-IR. It is demonstrated that when the copper concentration is fixed at 120 g/L, and the molar ratios of copper to zinc are set at 3∶2, 1∶1 and 2∶3, respectively, the crystals in the precipitation product consist of aurichalcite and malachite. As the molar ratio of copper to zinc decrease, the number of malachite crystals decrease. When the molar ratio of copper to zinc is 2∶3, a further reduction in the number of malachite crystals is observed when the copper concentration reduce from 120 g/L to 80 g/L. Finally, under the condition that the molar ratio of copper to zinc is 2∶3 and the copper concentration is 80 g/L, single-phase aurichalcite crystals are precipitated. This provides basic data for controlling the synthesis of aurichalcite by ammonia distillation method.

Preparation and Photoelectrochemical Cathodic Protection Properties of F-Doped SrTiO₃

WANG Jiansheng, KONG Cunhui, ZENG Xiongfeng, ZHAO Yingna

2024, 53(4):  707-713. 

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SrTiO₃ has great potential for applications in the photoelectrochemical cathodic protection field due to its suitable band structure and stable recombination characteristics, but the low utilization of sunlight and high recombination rate of photogenerated electron-hole pairs limit its further development. Based on this, SrTiO₃ was modification by doping anion (F) in order to obtain a new kind of SrTiO₃ photoanode material with efficient and stable photoconversion performance. F-doped SrTiO₃ photoanodes with different F doping concentrations were prepared by solvent thermal method. UV-Vis DRS and fluorescence spectrometer test results show that F doping improves utilization of sunlight and separation ability of photogenerated electron-hole pairs. The photoelectrochemical cathodic protection results are as follows: when F doping concentration is 2.0% (atomic fraction), the photocurrent density of F-2.0%-SrTiO₃ coupled with 304 stainless steel reaches 3.7 μA/cm², and the open-circuit potential of 304 stainless steel negatively moves to -0.42 V under light conditions, showing an effective protection for 304 stainless steel in simulated seawater.

Synthesis of Novel Aluminum Gallium Dihydrogen Phosphate Metal-Inorganic Framework and Its Catalytic Preparation of Butanolal from Acetaldehyde

CAO Yupeng, ZHANG Hanjie, HUANG Jiqing, GUO Wei, GONG Xubin, FANG Tao

2024, 53(4):  714-720. 

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Here, a novel aluminum-gallium-phosphate (GAHPO) metal-inorganic framework structure was prepared by hydrothermal method, and it was fully characterized by single crystal X-ray diffraction, powder X-ray diffraction, IR spectroscopy, and gravimetric analysis-differential scanning calorimeter (TG-DSC). Single crystal X-ray diffraction results show that GAHPO is attributed to the trigonal system and Rc3 space group. Al(Ga)O₆ octahedra and PO₄ tetrahedral structures is distorted to form one-dimensional chains, and then is stacked into three-dimensional metal-inorganic frameworks through hydrogen bonding. TG-DSC shows that GAHPO is of high thermal stability, with the initial decomposition temperature of 240 ℃. Compared with aluminum phosphate, the introduction of Ga³⁺ distorted the AlPO₄ lattice, thus weakening and elongating the Al—O bond, which makes more acid catalytic sites exposed and enhanced the catalytic activity. The experiment shows that when the reaction temperature is 60 ℃, and the catalyst dosage is 10% of acetaldehyde, GAHPO could catalyze the condensation of acetaldehyde to produce butanolal with good conversion rate (47%) and excellent selectivity (>99%). The reaction mechanism of acetaldehyde condensation catalyzed by GAHPO was investigated using scavengers, NH₃-TPD and specially designed derivatives to confirm the reactive sites of the catalyst and the substrate. This work provides a feasible way for novel aluminum inorganic framework structures and the catalytic applications.

Effect of Carbonization Temperature on Electrocatalytic Oxidation Methanol Performance of CF/Pd Catalysts

WANG Chenxing, LIU Yusong, HU Yongchi, HU Jiajun, ZHAO Yuchun, SONG Xuhui, SONG Yanyan

2024, 53(4):  721-729. 

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In order to investigate the effect of carbonization temperature on the electrocatalytic performance of CF/Pd catalysts for methanol oxidation, a series of CF/Pd catalysts were prepared by electrospinning heat treatment carbonization impregnation method. The carbonization temperatures were set at 800, 1 000, and 1 200 ℃, respectively. The obtained CF/Pd catalyst samples were characterized by microscopic morphology, composition analysis, and electrochemical testing. Research has found that at 800 ℃, PAN/CA fibers have completely carbonized, but as the carbonization temperature increases, the degree of fibrosis of CF/Pd catalysts gradually decreases, and the bonding phenomenon becomes more obvious. The electrocatalytic performance of methanol oxidation shows a trend of first increasing and then decreasing. When the carbonization temperature is 1 000 ℃, the CF/Pd catalyst has the best electrocatalytic performance for methanol oxidation, with a catalytic activity 5.4 times that of commercial Pd/C catalysts and a stability 16.2 times that of commercial Pd/C catalysts.

Theoretical Study on Design and Hydrogen Storage Properties of High-Valence Boron-Phosphorous Based COFs

WANG Yaodong, LI Xiaodong, YANG Penghui, ZHANG Huidong, LIU Xiuying, YU Jingxin

2024, 53(4):  730-738. 

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At present, the valence state (connectivity) of most covalent organic frameworks (COFs) building units is low, mostly trivalent and tetravalent, making only 18 types of topological structures of COFs materials. On the contrary, the valence states of MOFs building blocks vary from 3 to 24, making them have more than 2 000 topological structure types. If a higher valence COFs building block can be designed, it will greatly enrich its topological structure type and material number. To this end, a hexahedral boron-phosphorus unit (-B₄P₄O₁₂-) and five linear organic linkers (phenyl, fluorophenyl, toluene, naphthalene, biphenyl) were selected, and five high-valent boron-phosphorus covalent organic frameworks (BP-COFs) with lta topology were theoretically designed by molecular mechanics methods. The results show that the five materials have structural characteristics that are conducive to hydrogen storage applications, such as low density (0.52~1.17 g·cm^-3), large specific surface area (1 274.12~4 033.95 m²·g^-1) and high porosity (0.55%~0.78%). The Grand Canonical Monte Carlo (GCMC) method was used to predict the physical adsorption properties of hydrogen molecules on five materials at 298 and 77 K, and the structure-activity relationship between material structure and hydrogen adsorption properties was analyzed. The results show that the five BP-COFs materials have strong hydrogen adsorption capacity. Especially at 77 K, BP-COF-10 and BP-COF-11 have the best performance in hydrogen storage performance. BP-COF-10 has the highest volumetric hydrogen storage capacity at 77 K, reaching 52.86 g·L^-1. BP-COF-11 has a large accessible specific surface area and high porosity. It has a good hydrogen storage capacity at 77 K and a gravimetric hydrogen storage capacity of 9.90% at 5 000 kPa. With the increase of pressure, the hydrogen storage capacity of BP-COF-11 still maintains a good upward trend. BP-COF-7 has the largest hydrogen storage capacity at 298 K, and the hydrogen storage capacity reaches 4.83 g·L^-1 at 5 000 kPa. This indicates that the designed material has good hydrogen storage potential. This study will provide a theoretical reference for the experimental development of new high-performance hydrogen storage materials.