Trace sulfur promoted Fe,N-codoped carbon black as electrocatalyst for oxygen reduction reaction

Doping carbon materials with Fe and N attracts great attention due to its promising application in preparing ORR electrode with high performance and low cost. Previously, Fe, N-codoped catalyst (Fe/N/C) had been synthesized via a simple one-pot method using carbon materials, dopamine and FeCl₃ by our group. However, the unstable activity and low selectivity (electron transfer number of ∼3.5) are key problems that should be solved. Herein, trace sulfur has been introduced into Fe, N-codoped carbon black by using 2-mercaptoethanol as an adhesive sulfur precursor. By the doping of trace S atoms (∼0.25 at%) into Fe, N-codoped carbon frameworks, the ORR performance has been obviously improved simply without any re-treatment process, such as acid-etching or nitrogen supplement. The mechanism of this process has been systematically investigated by changing the amount of initial sulfur precursor. A moderate amount of trace sulfur can effectively enhance the ORR performance of Fe, N-codoped carbon black due to suitable interactions among Fe, N, S and C elements. Both the content and the state of Fe and N species on the surface of carbon black can be changed and controlled by trace sulfur. The as-synthesized 1.0 SFe/N/C catalyst exhibits a good ORR activity (E_1/2 = 0.749 V, J_k = 54.56 mA cm⁻²) and a total 4-electron selectivity. 1.0 SFe/N/C also shows better catalytic stability and methanol tolerance than 20 wt% Pt/C.     

Highly selective electrocatalytic hydrogenation of cinnamaldehyde over tin dioxide-supported palladium nanocatalysts

Selective hydrogenation of α, β-unsaturated aldehydes has always been a hot research topic owing to favorable thermodynamics in CC hydrogenation. In this work, a series of Pd/SnO₂ nanocatalysts were facilely synthesized under mild conditions, via the reduction of Na₂PdCl₄ by dimethylaminoborane. Under galvanostatic electrolysis at 3.33 mA cm^?2 for 8 h, the selective conversion of cinnamaldehyde (CAL) was achieved over Pd/SnO₂-coated carbon fiber in neutral phosphate buffer, giving the cinnamyl alcohol (COL) selectivity of 78.85% at the conversion of 84.88%. The Pd/SnO₂ nanocatalysts outperform commercial Pd/C catalysts, showing high COL selectivity and faradaic efficiency. The cathodic reduction potential of CAL over Pd_4·3/SnO₂ occurs at ?0.92 V. The SnO₂ support is beneficial to promote the CO adsorption of CAL and lower the HER activity of Pd nanocatalysts, thereby contributing to superior activity of Pd_4·3/SnO₂ for selective hydrogenation of CAL.     

Pedestrian injury analysis with consideration of the selectivity bias in linked police-hospital data

Evaluation of crash-related injuries by medical specialists in hospitals is believed to be more exact than rather a cursory evaluation made at the crash scene. Safety analysts sometimes reach for hospital data and use them in combination with the police crash data. One issue that needs to be addressed is the, so-called, selectivity (or selection) bias possible when data used in analysis are not coming from random sampling. If not properly addressed, this issue can lead to a considerable bias in both the model coefficient estimates and the model predictions. This paper investigates pedestrian injury severity factors using linked police-hospital data.A bivariate ordered probit model with sample selection is used to check for the presence of the selectivity bias and to account for it in the MAIS estimates on the Maximum Abbreviated Injury Scale (MAIS). The presence of the sample selection issue has been confirmed. The selectivity bias is considerable in predictions of low injury levels.The pedestrian injury analysis identified and estimated several severity factors, including pedestrian, road, and vehicle characteristics. Male and older pedestrians were found to be particularly exposed to severe injuries. Rural roads and high-speed urban roads appear to be more dangerous for pedestrians, particularly when crossing such roads. Crossing a road between intersections was found to be particularly dangerous behavior. The size and weight of the vehicle involved in a pedestrian crash were also found to have an effect on the pedestrian injury level. The relevant safety countermeasures that may improve pedestrian safety have been proposed.     

Recovery of manganese from iron containing sulfate solutions by precipitation

Worldwide consumption of manganese is increasing, nevertheless huge amounts of manganese from hydrometallurgical processes still end up as waste since the recovery of manganese from multi-metal solutions at low concentrations is not considered feasible. Poor iron control typically prevents the production of high purity manganese. This work studies a number of precipitants in manganese recovery and iron separation from sulfate solutions. The precipitation reagents were compared from the point of view of selectivity and economy. Carbonate precipitation is a fast and effective method for the recovery of manganese from bulk solutions. Subsequent leaching of metal carbonate is also easier and consumes less acid than, for example, hydroxide or sulfide precipitates. In order to avoid gypsum formation, soda ash should be used instead of limestone. It was found that efficient selective iron removal from MnSO₄ solutions is achieved with combined O₂ or air oxidation and CaCO₃ precipitation at pH >5.8 and at a redox potential of >200 mV. Effective mixing and sufficient retention time are essential to make the method technically efficient and economically feasible.     

Gemini型捕收剂对石英和磁铁矿的浮选性能

通过单矿物浮选试验,考察了Gemini型捕收剂Gemini-31503和十二胺对石英和磁铁矿的浮选特性,结果表明,Gemini-31503在较宽的pH范围里对石英具有很强的捕收能力,并且对石英具有良好的选择性,其性能明显优于十二胺。用Gemini-31503对石英和磁铁矿的人工混合矿进行反浮选,在不需再添加其他任何药剂的情况下取得了良好的分选指标。动电位测定和红外光谱分析结果显示,Gemini-31503在两种矿物表面的吸附主要为静电吸附,且在相同条件下,Gemini-31503在石英表面的吸附量比在磁铁矿表面的吸附量大。     

SiW12杂多酸盐在C4烷基化反应中应用的研究

用浸渍法制备了Cs ,K ,NH 4的SiW12杂多酸盐类和SiO2负载的SiW12杂多酸(SiW12/50%SiO2),在超临界(145℃,50kg/cm2)条件下评价了它们对异丁烷和丁烯烷基化的催化作用。结果表明,它们的活性和选择性大小顺序是:当阳离子数相同时,Cs 盐>K 盐>NH 4盐;在Cs 盐中,当Cs 离子数为2 5个时最好;总体比较SiW12/50%SiO2最优。但即使在超临界条件下,它们仍不能长周期运转。     

碳二加氢催化剂选择性快速评价法及其应用

从理论推导得出碳二加氢催化剂选择性快速评价法,并用此方法对三种碳二加氢催化剂选择性进行评价,并指出此快速评价法的独特应用。     

用于130nm/90nm新工艺开发的铜CMP阻挡层磨料系统(英文)

通过与实验室的CMP和集成工程师合作,采用测试系统观察两种或两种以上混合配方磨料的选择比。实验数据表明,通过改变单个化学试剂组分的浓度改变磨料的选择比效果突出,磨料配方师可以简便地修改磨料配方。这种方法的优点是,如果改变集成方法或特殊膜层,可以很快地重新优化磨料。如SiN膜取代TEOW淀积氧化物膜,对新系统可以容易地重新优化磨料。介绍了几种磨料组分浓度的去除速率和选择比。     

Liquid‐Phase Aerobic Oxidation of Benzyl Alcohol Catalyzed by Pt/ZrO2

The oxidation of benzyl alcohol by molecular oxygen in the liquid phase and catalyzed by Pt/ZrO2 using n‐heptane as the solvent was studied. Pt/ZrO₂ was very active and 100 % selective for benzyl alcohol conversion to benzaldehyde. The catalyst can be separated by filtration and reused. No leaching of Pt or Zr into the solution was observed. Typical batch reactor kinetic data were obtained and fitted to the Langmuir‐Hinshelwood, Eley‐Rideal and Mars‐van Krevelen models of heterogeneously catalyzed reactions. The Langmuir‐Hinshelwood model was found to give a better fit. The rate‐determining step was proposed to involve direct interaction of an adsorbed oxidizing species with the adsorbed reactant or an intermediate product of the reactant. H₂O₂ was also proposed to be an intermediate product. n‐Heptane was found to be an appropriate solvent in this reaction system.     

金刚石高成核选择比图形化技术

报道了一种新的金刚石薄膜选择生长图形化技术。首先用直流偏压增强的微波等离子体化学气相沉积（ＭＰＣＶＤ）对图形区域（Ｓｉ）高密度金刚石成核，接着对掩模区域（ＳｉＯ２）进行一次化学浅腐蚀，然后正常生长金刚石薄膜，得到表面光滑、侧壁陡直的金刚石精细图形。用该技术制作了金刚石微马达结构，其厚度为２μｍ，转子直径１５０μｍ。图形间隙可控制至１－２μｍ。