氢氧化钾活化制备可再生多孔碳及其电催化氧还原性能研究

氧还原反应缓慢的动力学过程严重限制了燃料电池的能量转换效率, 而商用Pt/C催化剂成本太高、资源稀缺、稳定性差, 需要寻找合适的材料来取代商用的Pt/C催化剂。近年来, 氮掺杂多孔碳材料因其独特的物理和化学特性吸引了大量的关注。本文使用富含氮元素的可再生土豆作为生物质前驱体, 通过简单的一步热解过程和KOH活化方法相结合制备出了一系列氮掺杂多孔碳电催化剂; 并系统研究了KOH用量和活化温度对碳基体孔结构和电催化性能的影响。结果表明, 当活化温度为750 ℃、KOH与碳的质量比为3/1时, 所制备的催化剂(NPC-750)的氧还原活性最高, 起始电位和半波电位分别达到0.89和0.79 V (vs. RHE), 极限电流密度达到5.53 mA?cm ^-2。NPC-750优异的氧还原催化活性主要归因于其发达的孔结构、高的比表面积(1134.2 m ²?g ^-1)和合适的氮含量(1.57at%)。同时, 优异的循环稳定性和抗甲醇中毒性能进一步说明这些生物多孔碳材料是潜在的低成本氧还原电催化剂。此外, 这些高比表面积多孔碳在超级电容、吸附/分离、催化以及电池等领域也具有潜在的应用前景。     

NaCl-template assisted preparation of porous carbon nanosheets started from lignin for efficient removal of tetracycline

We report here the preparation of lignin-based porous carbon nanosheets (LPCNS) using renewable lignin as a precursor and NaCl as a green template via a KOH activation for removing tetracycline (TC). Different techniques were employed to analyze the physicochemical properties of LPCNS. The LPCNS possessed high specific surface area of 3505?m² g^?1 and large pore volume of 2.0?cm³ g^?1. Moreover, the batch adsorption tests using LPCNS showed that the equilibrium adsorption amount was 1613?mg?g^?1 for TC at 298?K. Additionally, the LPCNS exhibited fast kinetics performance and good regeneration performance. This advanced carbon adsorbent with nanosheet structure showed enhanced adsorption performance compared to bulk carbon. This environment-friendly and low-cost salt-template strategy for the fabrication of carbon nanosheets hold promise to design biomass-based carbon nanosheets or even other sheet materials.     

提高硝基复合肥pH方法的研究

pH值是硝基复合肥的一项非常重要的指标。为满足生产需求,以高塔生产的硝氯基复合肥(16-16-16)和硝硫基复合肥(16-6-23)为实验对象,分别加入一定量的NH_2HCO_3、K_2CO_3、Na_2CO_3或KOH,测定其对肥料pH的提升效果。模拟正常生产过程,将NH_2HCO_3、K_2CO_3、Na_2CO或KOH加入到处于熔融状态下的样品中,检测其pH、总N含量。结果表明,添加NH_2HCO_3,成本低,对肥料的pH提升效果最明显,还能提高肥料总N含量。     

Nb2O5在KOH亚熔盐体系中的溶解行为

对Nb2O5在KOH亚熔盐体系中的溶解行为进行了研究,通过正交实验和因素实验分析了KOH浓度、反应温度、反应时间、搅拌速率和碱矿比等因素对Nb2O5在KOH亚熔盐体系中溶解行为的影响.结果表明:反应温度和KOH浓度是最重要的影响因素; 在一定温度下,KOH浓度越高越有利于得到可溶性的六铌酸钾; 而在一定KOH浓度下,温度越高越容易得到不溶性的铌酸盐沉淀.不溶性沉淀经ICP-AES和XRD分析证明为偏铌酸钾(KNbO3).     

KOH活化法制备废旧棉织物活性炭及表征

以废旧棉织物为原料,KOH为活化剂,利用化学活化法制备活性炭。采用XRD、SEM、元素分析仪、比表面积及孔径分析仪、FTIR等对所制备活性炭的结构与性能进行了分析与表征。结果表明:先炭化废旧棉织物,在m(炭化料)∶m(KOH)=1∶1,浸渍时间16 h,活化温度850℃,活化时间50 min的活化条件下,制备的活性炭比表面积为1 368.67 m~2/g,其中,微孔比表面积占BET比表面积的72.05%,总孔容为0.620 8 cm3/g,微孔孔容占总孔容的71.63%,微孔孔径主要分布在0.84~1.30 nm之间;活性炭呈中空纤维状,具有丰富的孔隙结构;碳质量分数高达90.43%;表面官能团主要为羧基、羰基、羟基等亲水性基团。废旧棉织物可作为制备活性炭的原料,所制活性炭性能优良。     

赤泥中浸出铌工艺条件的研究

对拜耳法生产氧化铝的富铌赤泥进行铌的碱浸工艺条件研究,考察赤泥粒度、氢氧化钾浓度、浸出温度、液固比对铌浸出率的影响。结果表明,当赤泥粒度-80μm,氢氧化钾浓度6mol/L,温度260℃,液固比61时,铌的浸出率可达到85%以上。铌的碱浸过程符合收缩未反应芯模型,浸出反应的控制步骤是固膜扩散控制。     

A novel method to tailor the porous structure of KOH-activated biochar and its application in capacitive deionization and energy storage

This study reveals a novel method to tailor the micro- and meso-porous structures of activated biochar by exploiting the interaction between pre-carbonization drying conditions and carbonization temperature in KOH activation. Biochar samples were mixed with concentrated KOH and then dried under air or nitrogen for various periods of time (0–280 h) followed by carbonization at 475, 675 or 875 °C. It is confirmed that by manipulating drying conditions and carbonization temperatures, the KOH activated biochar can have a predominantly microporous, mesoporous or a combined (micro/meso) porous structure. The surface area, micropore and mesopore volumes tailored between: 488–2670 m² g⁻¹, 0.04–0.72 cm³ g⁻¹, and 0.05–1.70 cm³ g⁻¹, respectively. The mechanism of porosity development was investigated by FTIR analysis suggesting conversion of KOH to K₂CO₃ due to different drying conditions as a major role in tailoring the structure. The application of activated biochar with tailored porosity was investigated for Electric Double Layer adsorption of NaCl/NaOH to be employed in water treatment (capacitive deionization) or energy storage (supercapacitor) processes. The majorly microporous activated biochar (N₂-dried activated at 675 °C) showed promising capacitances between 220 and 245 F g⁻¹. Addition of mesoporous structure resulted in capacitances between 182 and 240 F g⁻¹ with significantly reduced electrode resistance and improved capacitive behavior as evidenced by Impedance Spectroscopy and Galvanostatic Charge/Discharge tests.     

Extremely Strong and Transparent Chitin Films: A High‐Efficiency,Energy‐Saving,and “Green” Route Using an Aqueous KOH/Urea Solution

Crystalline polysaccharides are useful for important and rapidly growing applications ranging from advanced energy storage, green electronics, and catalyst or enzyme supports to tissue engineering and biological devices. However, the potential value of chitin in such applications is currently neglected because of its poor swellability, reactivity, and solubility in most commonly used solvents. Here, a high‐efficiency, energy‐saving, and “green” route for the fabrication of extremely strong and transparent chitin films is described in which chitin is dissolved in an aqueous KOH/urea solution and neutralized in aqueous ethanol solution. The neutralization temperature, ethanol concentration, and chitin solution deacetylation time are critical parameters for the self‐assembly of chitin chains and for tuning the morphology and aggregate structures of the resulting chitin hydrogels and films. Moreover, the drawing orientation can produce extremely strong and tough chitin films with a tensile strength, Young's modulus, and work of fracture of 226 MPa, 7.2 GPa, and 20.3 MJ m^?3, respectively. The method developed here should contribute to the utilization of seafood waste and, thereby, to the sustainable use of marine resources.     

Promoting highly dispersed Co3O4 nanoparticles onto polyethyne unraveling the catalytic mechanism with stable catalytic activity for oxygen evolution reaction: From fundamentals to applications

The solution to overcome the energy crisis in the globe with saving the environment from pollution and the community health, along with other applications of electrochemical for water splitting to get hydrogen and oxygen as a clean fuel. Likewise, the conducting polymers experience as stability over long time, or some time the breaking of conducting polymer chain is unavoidable with addition of polymer. For many reasons, we use noble metal co-catalysts in conjunction with semiconductors for improved hydrogen and oxygen gas production by the water splitting. The morphological characterization, & chemical composition of pristine & composite material studies with the help of different analytical techniques as like SEM, EDX, XRD, XPS & HRTEM. An outperform and active non-noble electrocatalyst for the oxygen evolution reaction which is a hotspot in the current research activities for oxygen & hydrogen production with zero carbon dioxide emission. Herein, we present an advanced material Co₃O₄/polyethyne for the first time to produce oxygen at a reasonable overpotential. The best oxygen evolution performance of Co₃O₄/polyethyne (20) providing the best performance at low overpotential 260 mV at 10 mAcm⁻² the Tafel slope 64 mVdec⁻¹, further strongly acceptable durability approximately for the 30 h & finally obtained charge transfer resistance value of 82.58 Ohms & greater capacitance 1.56 mF value for Co₃O₄. The key element in the success of newly developed catalyst is the greater amount of Co₃O₄ nanoparticles due to selective growth on polyethyne which has played a dominant role in oxygen production. It is because of the worth mentioning properties of polyethyne as a good electrical conductor, as efficient catalyst Co₃O₄ with more surface roughness and high surface area, which is strongly boosting the production of oxygen. The developed material can be applied in other competing fields such as lithium-ion batteries, solar cells, energy storage devices, and photochemical water splitting.     

Fabrication of microporous and mesoporous carbon spheres for high‐performance supercapacitor electrode materials

Microporous and mesoporous carbon spheres (CSs) were fabricated using resorcinol and formaldehyde as precursors in the presence of Pluronic F127 as porogen and KOH as the active agent. The textural characteristic and morphology were characterized by scanning electron microscopy, transmission electron microscopy, and N₂ adsorption/desorption techniques. Pluronic F127 played an important role for generating mesopores, while KOH activation brought abundant micropores and resulted in a combined microporous and mesoporous structure of the CSs. The results showed that a typical sample (denoted as CS‐F‐K) possessed a spherical shape, with a high specific surface area of 735.4 m²/g, large pore volume of 0.622 cm³/g, and combined microporous and mesoporous structure, which endowed CS‐F‐K good electrochemical performance with a specific capacitance of 182 F/g under a current density of 0.5 A/g, remarkable rate performance, and long‐term cycling stability. After 1000 cycles at 3 A/g, CS‐F‐K electrode can still remain the specific capacitance of 154.8 F/g with a retention of 98.9%. The excellent electrochemical performance of CS‐F‐K was mainly attributed to the micro‐mesoporous structure, which promoted the ion accumulation on the electrode surface and facilitated fast ion transportation. Copyright © 2015 John Wiley & Sons, Ltd.