碳载体空位工程助力原位合成的Pt纳米枝晶促进电催化氧气还原

质子交换膜燃料电池(PEMFCs)因其高能量密度、低操作温度和环保等特性,被视为极具潜力的能量转换系统.目前,碳载铂颗粒(Pt/C)是PEMFCs阴极氧还原反应(ORR)中使用最广泛的催化剂.然而,Pt与碳载体间的电子结构差异导致Pt纳米颗粒(Pt NPs)易从碳载体上脱落,严重降低了ORR的催化活性.此外,Pt的高成本和稀缺性也限制了其广泛应用.相比之下,Pt纳米枝晶(NDs)因具有高利用率的表面活性位点而备受关注.然而,Pt NDs的合成通常需要严格控制反应条件,且其与碳基底间的弱相互作用易导致活性位点损失和性能下降.因此,开发具有强金属载体相互作用的Pt复合碳催化剂对PEMFCs的实际应用至关重要.本文通过原位Cl-介导的生长策略,结合碳本征空位工程,成功制备了分散在富含碳本征空位的中空氮掺杂碳基底上的Pt NDs催化剂(Pt@HNC-V-800).拉曼光谱和电子顺磁共振光谱结果表明,碳本征空位的形成机制源于碳基底结构中氮原子的耗散,该过程引起碳原子的重新排列,进而产生了丰富的本征缺陷位点.X射线吸收光谱和X射线光电子能谱结果表明,与无碳空位的Pt@HNC催化剂相比,富含本征碳空位的样品(Pt@HNC-V-800)表现出较低的Pt-Pt键配位数(8.64)和更强的给电子效应.得益于Pt NDs丰富的活性位点及其与本征碳空位基底之间的强电子效应,Pt@HNC-V-800的ORR半波电位高达0.947 V,质量活性和比表面活性分别为1.55 A mg^(-1) Pt和1.85 mA cm^(-2),是商用Pt/C的8.2和6.8倍(0.191 A mg^(-1)Pt和0.27 mA cm^(-2)).加速耐久性测试结果表明,经20000次电势循环后,Pt@HNC-V-800的活性无明显变化,其活性损失远低于无碳本征空位的Pt@HNC材料和商业Pt/C催化剂.因此,与无碳本征空位的Pt@HNC材料相比,Pt@HNC-V-800的ORR活性和稳定性都有较大提升,进一步证实了碳本征空位工程协同Pt NDs策略的优越性.此外,密度泛函理论计算结果表明,Pt@HNC-V的丰富空位降低了氧中间体过电势,优化了ORR中间体在Pt NDs上的吸附能,进而提高了催化剂的ORR本征活性.同时,富碳本征空位的存在增强了Pt NDs在碳载体上的结合能,使Pt NDs不易在电势循环过程中脱离碳载体,从而增强了稳定性.综上所述,本文通过Pt NDs与碳本征空位工程协同效应策略,精准调控碳负载Pt基催化剂的结构,大幅提升其在酸性条件下的ORR性能,为进一步设计高性能的ORR电催化剂提供了新思路.

Deep decalcification of factory-provided freezing acidolysis solution to achieveα-high-strength gypsum

The freezing acidolysis solution of the nitric acid-phosphate fertilizer process has a high calcium content,which makes it difficult to produce fine phosphate and high water-soluble phosphate fertilizer products.Here,based on the potential crystallization principle of calcium sulfate in NH_(4)NO_(3)-H_(3)PO_(4)-H_(2)O,the deep decalcification(i.e.calcium removal)technology to achieveα-high-strength gypsum originated from freezing acidolysis-solutions has been firstly proposed and investigated.Typically,calcium can be removed from the factory-provided freezing acidolysis-solution by neutralizing it with ammonia,followed by the addition of ammonium sulfate solution.As a result,the formation of calcium sulfate in the reaction system undergoes the nucleation and growth of CaSO_(4)·2H_(2)O(DH),as well as its dissolution and crystallization into short columnarα-CaSO_(4)·0.5H_(2)O(α-HH).Remarkably,with the molar ratio of SO_(4)^(2-)/Ca^(2+)at 1.8,the degree of neutralization(NH_(3)/HNO_(3) molar ratio)at 1.7,the reaction temperature of 94℃,and the reaction time of 300 min,the decalcification rate can reach 86.89%,of which the high-strengthα-CaSO_(4)·0.5H_(2)O(α-HH)will be obtained.Noteworthy,the deep decalcification product meets the standards for the production of fine phosphates and highly water-soluble phosphate fertilizers.Consequently,the 2 h flexural strength ofα-HH is 5.3 MPa and the dry compressive strength is 36.8 MPa,which is up to the standard of commercialα-HH.

H_(2)O_(2)/Se改性钒催化剂制备及催化氧化SO_(2)性能研究

提出了一种H_(2)O_(2)/Se改性钒催化剂制备的新方法。采用XRF、XRD、SEM、MIP和TG/DSC对催化剂进行表征分析,测定了催化剂催化氧化SO_(2)转化率,并与国产钒催化剂CHP-75和进口VK-38对比分析。结果表明,H_(2)O_(2)/Se改性钒催化剂V@10%H_(2)O_(2)-Se/SiO;具有清晰的表面孔道、较大的孔容、较小的活性组分晶体尺寸和较低熔融相变温度,使其具有较高的催化氧化SO_(2)活性。该催化剂催化活性高于国产CHP-75,与进口VK-38媲美。高效钒催化剂的设计为国产钒催化剂替代国外进口催化剂提供了一种可能。

磷石膏对黄壤磷吸附性能及吸附动力学分析

研究了磷石膏(PG)对黄壤磷吸附能力的影响,并探讨其影响机制。以贵州省黄壤为研究对象,探索不同掺量的PG在不同培养时间等条件下对黄壤磷吸附性质的影响,并通过吸附动力学实验和数据模型拟合分析了PG对黄壤磷吸附动力学行为的影响。结果表明:PG掺量对黄壤磷吸附量影响显著(P<0.05)。磷吸附量随PG掺量增加呈先增加后降低趋势,掺量为0.5 g/100 g土时达最高值,与原土相比,磷吸附量提高2.80%,pH由3.77升至4.00,无定型氧化铁(Feo)含量上升2.33%;PG掺量分别为0.5 g/100 g土和1.0 g/100 g土的混合土样磷吸附动力学过程符合准一级方程,之后,随掺量增加混合土样磷吸附动力学过程符合准二级方程;磷石膏对黄壤磷吸附能力的影响在前7天最为显著,且磷石膏中Na2SO4、NaH2PO4和CaSO4对黄壤磷吸附能力起促进作用,NaF对黄壤磷吸附能力起抑制作用。

改性高岭土对工业氯化钙中Cu^(2+)和Pb^(2+)的吸附去除研究

采用煅烧结合氢氧化钠处理的方式对高岭土进行改性,在通过FT-IR、XRD、XRF等表征手段分析高岭土改性前后理化性质变化基础上,对改性高岭土吸附去除氯化钙溶液中Cu^(2+)和Pb^(2+)进行研究。讨论了吸附时间、氯化钙溶液pH和吸附剂用量对高岭土和改性高岭土吸附去除氯化钙溶液中Cu^(2+)和Pb^(2+)的影响,研究了改性高岭土在氯化钙溶液中吸附去除Cu^(2+)和Pb^(2+)的吸附动力学和等温吸附过程行为。研究发现,改性使高岭土发生非晶化转变,负电性、比表面积和孔容增大;在吸附时间40~120 min区间内,改性高岭土对氯化钙溶液中Cu^(2+)和Pb^(2+)的平均吸附容量比高岭土高了3.57和3.17 mg/g,且吸附容量随吸附时间增加而提高并渐趋平衡;对氯化钙溶液中Cu^(2+)的吸附容量随溶液pH增大先提高后降低,对Pb^(2+)的吸附容量随溶液pH增大逐渐增大;随着吸附剂用量增加,氯化钙溶液中Cu^(2+)和Pb^(2+)的吸附容量逐渐降低;改性高岭土对Cu^(2+)和Pb^(2+)的吸附过程符合拟二级动力学方程和Langmuir等温吸附模型。

Enhancing the hydration reactivity of hemi-hydrate phosphogypsum through a morphology-controlled preparation technology

The distribution of water channels in the crystal morphology of type-α hemi-hydrated gypsum(α-HH) was theoretically detected to investigate the effect of water channels on the hydration reactivity of hemi-hydrate phosphogypsum(HPG). Results showed that water channels were mainly distributed in the cylinders of α-HH crystal,whereas no water channel existed in the conical surfaces parallel to the z-axis. Increasing the number of water channels was critical to enhance the hydration activity of HPG compared with the hydration reactivity of industrial HPG and type-α high-strength gypsum. Controlling the technological parameters of crystallization by concentration of liquid-phase SO_4^(2-) made it possible to obtain HPG which had the stumpy crystals of α-HH and high hydration reactivity.

Distribution Characteristics of Air Anions in Beidaihe in Different Ecological Environments

Qinhuangdao is a provincial municipality under the jurisdiction of Hebei Province and a coastal city in China. Beidaihe is a district under the jurisdiction of Qinhuangdao and is a famous seaside scenic area. Alliance Peak, located in Beidaihe seashore scenic West. Jinshan mouth is the peak of the Union Peak, located in the easternmost Beidaihe waterfront. In this paper, we use the observed data of air negative ions in the Beidaihe, Qinhuangdao, Jinshanzui and Lianfeng Mountains for seven years to study the distribution characteristics of negative air ions in different ecological environments through meteorological observation. Research shows that the annual mean of air anion concentration fluctuates less. The annual mean is 1730 ind·cm-3, and the difference between the highest and lowest concentrations is 535 ind·cm-3. The average air anion concentration was the highest in August at 7785 ind·cm-3 and the lowest in January at 365 ind·cm-3. Negative air ions have obvious spatial characteristics, and negative ion concentrations of the sea and forest air are significantly high. The average annual mean of the sea is 3902 ind·cm-3, and that of the forest is 5403 ind·cm-3. The concentration of air anion changes daily, and daytime concentration is significantly lower than nighttime concentration. The highest peak appears at night or in the morning, while the lowest value appears between noon and afternoon. Inter-annual features and concentration of negative air ions, as well as annual rain days, total rainfall, thunderstorm days, and average relative humidity, are negatively related to the annual average temperature and sunshine hours. However, in the average concentration of negative air ions, the average correlation test of meteorological elements was insignificant. The air anion concentration is negatively correlated with the PM2.5 concentration of fine particulate matter. The concentrations of nitrogen dioxide, sulfur dioxide, and carbon monoxide in the fine particulate matter are negatively correlated with the ozone concentration, which is positively correlated with ozone concentration and is tested by significance. Atmospheric discharge (thunderstorm) can produce a considerable amount of air anion. Air negative ions are an important indicator of air quality, which is of great significance to the living environment. The distribution of negative ions in the study space and its influencing factors in order to provide a basis for air quality assessment in the region and provide references for the long-term research on air anion in different urban areas.

Evolution and significance of the psychosomatic model in gastroenterology

The biomedical model,which limits itself to finding the attributions of organic disease,is challenged by gastrointestinal(GI)symptoms.Simultaneously,physicians'attribution of GI symptoms to underlying psychological issues is not readily accepted by patients and can negatively affect the clinical rapport between doctor and patient.In reality,psychosocial aspects are involved in many functional disorders and organic diseases,not just in mental disorders.Time is overdue for gastroenterologists to recognise the inadequacy and limitations of conventional gastroenterology and consider the role of psychological,social and biological variables throughout the entire clinical course of the illness,as is shown in George Engel’s model.This review discusses the following:(1)the current challenges of using the conventional clinical model for both functional and organic GI illness,(2)the inadequacy and limitations of explaining GI symptoms simply as psychological disorders,(3)the exploration of the symptom-centred,stepped reattribution clinical model,(4)the clarification of psychosomatic medical concepts for use in gastroenterology,and(5)the significance of a systematic and interdisciplinary framework for a comprehensive psychosomatic model in gastroenterology.

Acute and Sub-Acute Toxicological Evaluations of Bioactive Alkaloidal Extract from Melodinus henryi and Their Main Chemical Constituents

Melodinus henryi is a good source of terpenoid indole alkaloids,and traditionally used as a folk medicine in the treatment of meningitis and fracture.In order to further exploit their potential uses,its anti-inflammatory and immunosuppressive activi-ties,safety evaluations and chemical profiles have been illustrated.Compared to the crude methanol extract from M.henryi and its non-alkaloidal fraction,the total alkaloidal fraction(MHTA)had the strongest anti-inflammatory and immunosup-pressive activities.In the acute oral toxicity assay,the half lethal dose(LD50)of MHTA was more than 2000 mg/kg.The sub-acute toxicity assay for consecutive 28 days exhibited MHTA at a lower concentrations of less than 500 mg/kg might be regarded as safe,and might damage spleen,liver,kidney,and heart when the dose is higher than 1000 mg/kg.In addition,a phytochemical investigation on MHTA led to the isolation of 15 monoterpenoid indole alkaloids.Thus,in regard with the potent side effects of MHTA,it should be used with caution in the development of phytomedicine.

Analysis of Farmers' Needs for Forestry Information and Technology in Yunnan's Hot Zone: Based on Empirical Survey in Menglian County

Lack of public forestry information and techniques has restricted the development of forestry management and the income increase of rural farmers in hot region of Yunnan province. Therefore it is necessary to provide forestry information and techniques to rural areas so as to compensate for the information gap between urban and rural areas. Based on the survey about farmer demand for information and technique in Menglian County,the paper analyzed the supply methods and demand characteristics of forestry information and techniques. The results showed that the farmers had very strong demands for forestry information and techniques with diversified trend. But the farmers got the information with backward method and single service supply approach,and it lacked effective expression mechanism for their demands.

Separation and recovery of associated rare earths from the Zhijin phosphorite using hydrochloric acid

The separation and extraction of associated rare earths from the Zhijin phosphorite mine is of great interest. Based on previous studies, the hydrolysis of phosphate ore using hydrochloric acid was systematically studied through extensive testing. Experiments were conducted to separate and recover the rare earths from the hydrolysis solution. Kinetic studies on the acidolysis of phosphorite using hydrochloric acid show that the use of hydrochloric acid in the acidolysis of phosphorite is mainly controlled by a chemical reaction and is also a diffusion-controlled reaction. When 210 L of HCL per 100 kg of phosphorite was used at 30 ℃ for 360 min, 96.1% of the P_2 O_5 and 95.0% of the rare earths are leached from the phosphorite. After defluorination and purification, the pH of the phosphate-acid solution is adjusted to 2.1 using sodium hydroxide, and a rare earth concentrate with rare earth content of 1.76 wt%is obtained; i.e., 90.1% of the rare earths are recovered. The rare earth content is increased to more than5 wt% through multiple enrichment processes, with a total yield of 59.5%.

Migration behavior, separation and recycling of rare earth during thermal decomposition of Zhijin phosphorus ore

Zhijin phosphorus ore is a moderate and low-grade phosphorus rare-earth ore contained in mines. The separation and extraction of associated rare earth are important research topics. In this study, the migration behavior of rare earth during the thermal decomposition of Zhijin phosphorus ore and the separation and extraction of rare earth in phosphorus slag are discussed systematically. During the thermal decomposition process of phosphorus ore, almost all of the associated rare earth enters into the phosphorus slag phase but does not enter into the ferrophosphorus or gas phases. Amorphous calcium metasilicate and calcium fluosilicate are major components of phosphorus slag, and rare earth mainly exists as a calsil solid solution. Hydrochloric acid was used for acidolysis of the phosphorous slag. Under the following conditions, 96% of the rare earth in the phosphorous slag can be dissolved in the acidolysis solution： acid excess coefficient of 1.5, reaction time of 50 min and reaction temperature of 50℃. The rare earth in the acidolysis solution was separated and recycled using oxalic acid as a precipitator and NaOH as a pH modifier. At pH of 1.7, rare-earth-enriched matter with rare-earth content of 2.1 wt% was obtained, and the recovery of the rare earth was 88%.