X射线光电子能谱对预硫化型催化剂活化过程的分析研究

在优选的离子枪刻蚀条件下,采用X射线光电子能谱深度剖析技术对不同活化时间的预硫化型催化剂进行深度剖析,分析不同活化时间对催化剂表面活化程度的影响。结果表明,预硫化型催化剂活化过程中伴随着表面氧化,且随着活化时间的延长,表面氧化程度加深;预硫化型催化剂活化3 h以后,表面基本硫化完全,随着活化时间的延长,硫化过程逐渐从表面向内部深入,同时表面氧化程度加深。     

Optimization of Activated Carbon Sulfurization to Reach Adsorbent with the Highest Capacity for Mercury Adsorption

This work deals with the use of elemental sulfur immobilized on the activated carbon surface, as an active phase to enhance the sorbent's mercury adsorption capacity. The sulfurization procedure was optimized, and the influence of two factors (temperature and initial ratio of sulfur to carbon), on the final properties and mercury adsorption capacities of the adsorbents was investigated. The sulfurized adsorbents were characterized using CHNS/O elemental analysis, surface area and porosimetry, FT-IR spectroscopy, SEM-EDS, and pH_pzc measurement. A series of batch studies were also conducted to delineate the effect of contact time, initial pH, solution temperature, and initial mercury concentration on the adsorption capacity of the adsorbents. Furthermore, attempts were made to desorb mercury from the metal loaded adsorbents using various concentrations of KCl, KBr and KI solutions.     

硼酸锂包覆改性尖晶石锰酸锂的研究

尖晶石型锰酸锂由于具有优异的安全性能且成本低廉,成为锂离子电池正极材料的研究热点。然而,由于锰溶解所导致的循环性能衰退是锰酸锂发展的主要障碍。随着温度的升高,锰溶解加剧,因而电池在高温条件下衰退更加严重。将硼酸锂包覆于锰酸锂表面,可以抑制锰的溶解。通过高能球磨的方法可将硼酸锂均匀地包覆于锰酸锂表面。X射线衍射与电化学阻抗表征结果表明,硼酸锂不会引起锰酸锂结构的变化和电池阻抗的增加。通过对界面转移电阻的研究发现,硼酸锂包覆量超过2%（质量分数）时电池的极化会增加,因此将硼酸锂的最佳包覆量控制在2%。相比于未经包覆的锰酸锂,经包覆的锰酸锂不论是对锂半电池还是对石墨全电池均表现出优异的循环性能,尤其是在60 ℃下的循环性能大大改善。软包全电池体积能量密度达到308 W·h/L,1C循环200次后容量保持率可达到94.7%。通过硼酸锂包覆可有效抑制锰酸锂的锰溶解,改善其循环性能。     

Sulfurization of carbon surface for vapor phase mercury removal - I: Effect of temperature and sulfurization protocol

The uptake of hydrogen sulfide by carbon materials (ACFs and BPL) under dry and anoxic conditions was tested using a fixed bed reactor system to determine the effects of sorbent properties, temperature (200-800 °C) and sulfurization protocols on the sulfur content, sulfur stability, sulfur distribution, and to elucidate possible reaction mechanisms for the formation of sulfur species. Sorbents with higher surface areas showed higher uptake capacity, indicating that active sites for sulfur bonding are formed during the formation of the pore structure. The sulfur content and stability generally increased with the increase in temperature due to a shift in the reaction mechanism. The sulfurization process is associated with the decomposition of surface functionalities, which creates active sites for sulfur bonding. The presence of H₂S during the cooling process increased the sulfur content by increasing the presence of less stable sulfur forms. Sulfurized sorbents produced at high temperatures have pore structure similar to that of the virgin carbons.     

A comparison of solid electrolyte interphase (SEI) on the artificial graphite anode of the aged and cycled commercial lithium ion cells

The commercial lithium ion cells with LiCoO₂ as cathode, artificial graphite as anode and 1 M LiPF₆/EC-DEC-EMC (ethylene carbonate-diethyl carbonate-dimethyl carbonate) (1:1:1, v/v/v) with additives (1 wt.% vinylene carbonate (VC) + 1 wt.% propylene sulfite (PS)) as electrolyte were aged at 60% and 100% state of charge (SOC) for 6 months at room temperature and the corresponding cycle performance was measured. Charge/discharge results showed that the capacity retentions after 100 cycles were in the order of fresh cell >60% SOC > 100% SOC. The composition of SEI on the anode was analyzed by X-ray photoelectron spectroscopy (XPS) and the sulfur atom in PS was used as a tagged atom in XPS analysis. The results suggested that the transformation of organic species to inorganic species and the species containing sulfur atom from the reduction of PS was dissolved for the cells aged at 60% and 100% SOC. The SEM and XPS surface and depth profile analysis showed that the increase of the thickness of SEI layer and the variation of compositions on storage or cycling, is one of the most important reasons that results in the deterioration of the cycle performance of commercial lithium ion cells aged at 60% and 100% SOC at room temperature for 6 months.     

水热法脱除碳酸锂中微量硫杂质的研究

以工业级碳酸锂为原料,采用水热法脱除其中的微量硫杂质制备电池级碳酸锂,探究了水热温度、水热时间对硫杂质脱除效果的影响。利用扫描电子显微镜（SEM）、X射线衍射（XRD）、X射线光电子能谱（XPS）等方法对产物形貌和结构做了表征。研究结果表明,硫杂质主要以Li2SO4形式存在,吸附在碳酸锂表面;水热过程改善了碳酸锂的结晶性,减少了晶体表面活性位点,降低了表面硫杂质的吸附量。在温度为140 ℃、水热反应4 h后碳酸锂质量分数提高至99.8%,SO42-的质量分数降至6.30×10-4,均符合电池级碳酸锂行业标准（YST 582—2013）。     

器外预硫化耐硫变换催化剂的研制

探讨了器外预硫化耐硫变换催化剂的制备方法,研究了不同硫化剂以及硫化剂的加入方式、浸渍方法、硫化温度和时间对催化剂活性的影响,同时考察了该催化剂的储存性能。结果表明,以本实验采用的单质硫、有机多硫化物A和助剂K2溶于溶剂D1作为硫化剂,并在120℃时以共浸法浸渍4h制备的器外预硫化耐硫变换催化剂,在密闭条件下储存性能较为稳定,活性优于传统的固定床硫化的催化剂。     

Effect of periodic precursor on sulfurization process of Cu2ZnSnS4 thin film

In this study, Cu₂ZnSnS₄ (CZTS) thin films were fabricated by periodically sequential depositions of metallic precursors by magnetron sputtering followed by sulfurization. The element compositions, crystal structures, and surface morphologies of the single-period precursor (Zn/Sn/Cu) and four-period precursor (Zn/Sn/Cu/Zn/Sn/Cu/Zn/Sn/Cu/Zn/Sn/Cu) during the sulfurization process were investigated. The experimental results showed that in the initial stage of sulfurization, the single-period precursor had a more efficient reaction with sulfur vapor below 300?°C because of its thicker metal layers. During the process of sulfurization, the CZTS phase first formed in the four-period film at 400?°C, owing to the wide distribution of the internal layer in the periodic thin film. With a further increase in temperature, the crystallinity of CZTS was enhanced and the secondary phases were reduced. A CZTS phase with Cu-poor and Zn-rich composition was confirmed in both thin films after complete sulfurization. The CZTS thin film with a four-period precursor showed a better degree of crystallization, and a single phase of CZTS was obtained more easily than in the single-period thin film. Therefore, using a periodic structure can promote the sulfurization reaction of Cu-Zn-Sn precursors and enhance the properties of CZTS thin films.     

The electrochemical performance of lithium–sulfur batteries with LiClO4 DOL/DME electrolyte

The electrochemical performance of lithium–sulfur batteries with LiClO₄ DOL/DME as electrolyte was investigated. Impedance and SEM analysis indicated that too high content of DME(Dimethoxy ethane) in electrolyte could raise the interfacial resistance of battery due to the impermeable layer formed on the surface of the sulfur cathode, which led to bad cycle performance, while the increase of DOL(1,3-dioxolane) could change those phenomena. The optimal composition of electrolyte was DME:DOL = 2:1 (v/v). With this electrolyte, the lithium–sulfur battery obtained a high initial discharge capacity of 1,200 mA h g^?1 and still remained 800 mA h g^?1 after 20 cycles.     

微波固相法制备铁酸锌脱硫剂的硫化动力学

通过微波与常规固相法制备了铁酸锌高温煤气脱硫剂,使用X射线衍射（XRD）、氮吸附、扫描电子显微镜（SEM）以及X射线光电子能谱（XPS）对两种不同焙烧方式制备的脱硫剂的物相组成、织构形貌和表面元素进行了表征。数据显示微波焙烧制备的脱硫剂具有孔隙结构丰富、表面金属元素含量高、结合能低等优点。使用热天平对铁酸锌脱硫剂硫化行为进行了研究,根据等效粒子模型计算了两种脱硫剂与硫化氢气体反应的动力学参数,得到了硫化反应动力学方程,并在固定床上对其煤气脱硫性能进行了考察。结果表明硫化过程分为化学反应控制区和颗粒内扩散控制区。微波焙烧制备脱硫剂的化学反应活化能和颗粒内扩散活化能较低,说明其在硫化氢气体脱除上具有更高的活性。在模拟煤气气氛下,相比常规焙烧方法制备的脱硫剂,微波制备的脱硫剂的脱硫性能显著提高,具有更高的硫容和更长的精脱硫时间。     

Kinetic investigation of sulfurized polyacrylonitrile cathode material by electrochemical impedance spectroscopy

To understand more about the sulfur composite prepared by sulfurized polyacrylonitrile at 300 °C, electrochemical impedance spectroscopy (EIS) is employed to investigate the electrochemical properties of the sulfur composite cathode during discharge process. The impact of discharge depth on the performance of sulfur composite materials is investigated. The electrolyte solution resistance, the charge transfer resistance and the interface impedance are evaluated from the EIS analysis. The charge transfer resistance and the interface impedance increase during delithiation and decrease during lithiation, while the concentration of Li⁺ in the composite decreases and increases, respectively. Meanwhile the electrolyte solution resistance is likely to keep stable. The interface resistance and charge transfer resistance of the sulfur composite cathode decrease rapidly after initial lithiation, while Li⁺ diffusion coefficient and exchange current density increase rapidly. After the initial lithiation, they are likely to keep stable. This study reveals more characteristics of the sulfur composite, which is considered to be a promising candidate for large capacity cathode material.     

Band gap tailoring of hydrothermally synthesized WS2 nanoparticles by the sulfurization time duration

In current study, WS₂ nanoparticles were systematically synthesized by hydrothermal method. After successful growth, the effect of sulfurization time duration on various optical parameters such as band gap, absorbance, admittance and refractive index was investigated by sulfurization the grown samples for different time durations (0–1 h). XRD patterns have confirmed the pure phase formation of WS₂ nanoparticles having crystallite size in the range of 24.4–29.26 nm. SEM images showed the flakes like structures which becomes more visible in combination with rectangular shapes when sulfurization time duration was increased. Synthesized WS₂ nanoparticles have been further studied to see their optical properties as a function of sulfurization time duration. All the synthesized samples showed high absorption and low transmission in UV/near visible region at wavelength of 550 nm. By increasing the sulfurization time duration, crystallinity of sulfurized nanoparticles increased which resulted in the decreases of transmission. Optical parameters such as refractive index and the extinction coefficient were also found to be greatly affected by sulfurization. Optical band gap of synthesized nanomaterials have been found to decreases from 2.98 to 2.19eV with increasing sulfurization time duration.     

氧对不同硫化状态钴钼耐硫变换催化剂性能的影响

对硫化态钴钼耐硫变换催化剂和采用特殊钝化技术制备的预硫化耐硫变换催化剂在大气中的变化进行研究。考察了与空气接触时间和温度对其催化性能的影响以及模拟工业装填条件下床层温升。结果表明,硫化态钴钼耐硫变换催化剂必须进行氮气条件下包装、运输和装填,而采用特殊钝化技术制备的预硫化耐硫变换催化剂无需氮气保护。     

Electrochemical improvement of low-temperature petroleum cokes by chemical oxidation with H2O2 for their use as anodes in lithium ion batteries

The electrochemical performance of non-graphitized petroleum cokes has been improved by mild oxidation using hydrogen peroxide, a procedure used for the first time in these materials. For this purpose, various carbonisation temperatures and H₂O₂ treatments were tested. For low sulfur content cokes, the aqueous oxidative treatment significantly increases the capacity values above 372 mAh/g during the first cycles. In contrast, cokes with a sulfur content of ca. 5%, did not shown a real improvement. The former results have been interpreted in terms of an effective oxidation of the particles surface, which removes unorganized carbon, where lithium can be irreversibly trapped. Moreover, a stable and less resistive passivating layer grows during the first discharge of lithium, as revealed by impedance spectroscopy. Therefore, chemical procedures, as mild oxidation, open an interesting field of research for the improvement of disordered carbons as anode materials in lithium ion batteries.     

二氯二甲基硅烷对锂硫电池性能的影响

采用二氯二甲基硅烷对锂片表面进行预处理,以提高电极的界面稳定性。将预处理的锂片与硫电极组装成锂硫电池,并对其进行充放电测试。结果表明,与以未经预处理锂片作负极的锂硫电池相比,经二氯二甲基硅烷预处理5 min的锂片作负极的锂硫电池的循环性能、倍率性能及库伦效率均得到较大的改善,且预处理时间对电池的性能有一定的影响。     

碱木素硫化反应以及木素酚醛树脂固化性能的研究

在碱性条件下对麦草碱木素进行硫化处理 ,降低其平均相对分子质量 ,脱除部分甲氧基 ,并增加芳香环上可反应官能团含量 ,以达到增加其反应活性的目的。实验表明 ,在硫用量 4%、加碱量 1 %、反应温度1 90℃、保温时间 1 5min条件下 ,获得的改性碱木素与苯酚、甲醛在酸性条件下反应制得的树脂具有较好的固化强度。     

器外预硫化催化剂加氢脱酸性能研究

为探索器内硫化与器外预硫化催化剂的催化活性,采用等体积浸渍法制备同一批次镍-钨氧化态催化剂,分别采用器内硫化与器外预硫化得到3种不同的催化剂,考察3种新鲜催化剂的物化性质、催化活性和使用后催化剂的物化性质。结果表明：随着催化剂上硫化物负载量增加,预硫化催化剂的表观密度增加,比表面积、孔容、平均孔径均降低,同时预硫化催化剂在各个孔径范围内的分布均降低;3种催化剂中高负载硫的器外预硫化催化剂上W ⁴⁺态金属和NiWS活性相原子分数最高,器内硫化催化剂次之,低负载硫的器外预硫化催化剂最低;在反应压力为3.0 MPa、空速为1.0 h ^-1、氢油体积比为400∶1条件下,以绥中常二线、减三线馏分油为原料在不同反应温度下评价催化剂的活性,高负载硫的器外预硫化催化剂的脱酸、脱硫、脱氮活性最高,器内硫化催化剂次之,低负载硫的器外预硫化催化剂的催化活性最差。     

Effect of sulfur annealing on the morphological,structural, optical and electrical properties of iron pyrite thin films formed from FeS<Subscript>2</Subscript> nano-powder

Iron pyrite (FeS₂) thin films were fabricated by spin coating the solution of FeS₂ nanocrystals of ～40 nm in size on glass substrates, followed by annealing in a sulfur environment at different temperatures. The effect of sulfurization temperature on the morphology, structural, optical and electrical properties was investigated. With increase of the sulfurization temperature, the grain size and crystallinity of the films was improved, although some cracks and voids were observed on the surface of thin films. The band gap of the FeS₂ films was decreased at higher sulfurization temperature. The electrical properties were also changed, including the increasing in resistivity and the decrease in Hall mobility, with increase of sulfurization temperature. The change in the optical and electrical properties of the FeS2 thin films was explained based on the changes of phase, morphology, surface, and grain boundary property.     

Li_(1.02)Mn_(1.92)Al_(0.02)Cr_(0.02)Mg_(0.02)O_(4-x)F_x尖晶石正极材料的研究

采用溶胶-凝胶法合成了复合离子掺杂的尖晶石型锰酸锂Li1.02Mn1.92Al0.02Cr0.02Mg0.02O4-xFx(x=0,0.06)正极材料,并用XRD、CV、EIS和充放电测试等研究了其结构和电化学性能。结果表明,F与金属离子(Li、Al、Cr、Mg)的复合掺杂不仅提高了材料的比容量,还增加了尖晶石结构的稳定性,改善了材料的循环性能和可逆性能;充放电测试结果表明,Li1.02Mn1.92Al0.02Cr0.02Mg0.02O3.94F0.06具有优越的循环性能,常温下,以1/3C充放电的首次放电容量及50个循环后的容量保持率分别为117.9 mAh/g,96.9%。     

Anode materials for lithium ion batteries from mild oxidation of natural graphite

Mild oxidation of a natural graphite in an ammonium peroxydisulfate solution yields promising anode materials. X-ray photoelectron spectroscopy, FTIR spectroscopy, electron paramagnetic resonance, thermogravimmetry, differential thermal analysis, high resolution electron microscopy and surface area measurements provided results suggesting that oxidation eliminates some reactive structural defects in this graphite. In addition, the surface of natural graphite is recoated with a dense layer of oxides forming an effective passivating film to prevent the decomposition of electrolyte and the movement of graphene molecules along its a-axis. Consequently, its thermostability and the EPR signal increase. In addition, the numbers of nanosized pores and channels increases, which provide more inlets and outlets for lithium intercalation and deintercalation and more sites for lithium storage. As a result, the reversible lithium capacity and the coulombic efficiency in the first cycle increase significantly and the cycling behaviour improves markedly. The reproducibility of product properties can be well controlled, and this method is promising for industry.