Tuning the surface electronic structure of noble metal aerogels to promote the electrocatalytic oxygen reduction

The sluggish kinetics of the oxygen reduction reaction(ORR)is the bottleneck for various electrochemical energy conversion devices.Regulating the electronic structure of electrocatalysts by ligands has received particular attention in deriving valid ORR electrocatalysts.Here,the surface electronic structure of Ptbased noble metal aerogels(NMAs)was modulated by various organic ligands,among which the electron-withdrawing ligand of 4-methylphenylene effectively boosted the ORR electrocatalysis.Theoretical calculations suggested the smaller energy barrier for the transformation of O^(*) to OH^(*) and downshift the d-band center of Pt due to the interaction between 4-methylphenylene and the surface metals,thus enhancing the ORR intrinsic activity.Both Pt3Ni and Pt Pd aerogels with 4-methylphenylene decoration performed significant enhancement in ORR activity and durability in different media.Remarkably,the 4-methylphenylene modified Pt Pd aerogel exhibited the higher halfwave potential of 0.952 V and the mass activity of 10.2 times of commercial Pt/C.This work explained the effect of electronic structure on ORR electrocatalytic properties and would promote functionalized NMAs as efficient ORR electrocatalysts.

Facile electrochemical surface-alloying and etching of Au wires to enable high-performance substrates for surface enhanced Raman scattering

Surface-enhanced Raman Spectroscopy(SERS)is a nondestructive technique for rapid detection of analytes even at the single-molecule level.However,highly sensitive and reliable SERS substrates are mostly fabricated with complex nanofabrication techniques,greatly restricting their practical applications.A convenient electrochemical method for transforming the surface of commercial gold wires/foils into silver-alloyed nanostructures is demonstrated in this report.Au substrates are treated with repetitive anodic and cathodic bias in an electrolyte of thiourea,in a one-pot one-step manner.X-rays absorption fine structure(XAFS)spectroscopy confirms that the AuAg alloy is induced at the surface.The unique AuAg alloyed surface nanostructures are particularly advantageous when served as SERS substrates,enabling a remarkably sensitive detection of Rhodamine B(a detection limit of 10^(-14)M,and uniform strong response throughout the substrates at 10^(-12)M).

A general synthetic strategy for N, P co-doped graphene supported metal-rich noble metal phosphides for hydrogen generation

The exploitation of electrocatalysts with high activity and durability for HER is desirable for future energy systems,but it is still a challenge.NMPs have attracted increasing attentions,but the preparation process often needs toxic regents or dangerous reaction conditions.Herein,we develop a general green method to fabricate metal-rich NMPs anchored on NPG through pyrolyzing DNA cross-linked complexes.The obtained Ru_(2) P-NPG exhibits an ultrasmall overpotential of 7 mV at 10 mA cm^(2) and ultralow Tafel slope of 33 mV dec^(-1) in 1.0 mol L?1 KOH,even better than that of commercial Pt/C.In addition,Ru 2 P-NPG also shows low overpotentials of 29 and 78 mV in 0.5 mol L^(-1) H_(2)SO_(4) and 1.0 mol L^(-1) PBS,respectively.The superior activity can be attributed to the ultrafine dispersion of Ru 2 P nanoparticles for more accessible sites,more defects formed for abundant active sites,the two-dimensional plane structure for accelerated electron transfer and mass transport,as well as the regulation of electron distribution of the catalyst.Moreover,the synthetic method can also be applied to prepare other metal-rich noble metal phosphides(Pd_(3)P-NPG and Rh_(2)P-NPG),which also exhibits high activity for HER.This work provides an effective strategy for designing NMP-based electrocatalysts.

Advances in Noble Metal-Decorated Metal Oxide Nanomaterials for Chemiresistive Gas Sensors:Overview

Highly sensitive gas sensors with remarkably low detection limits are attractive for diverse practical application fields including real-time environmental monitoring,exhaled breath diagnosis,and food freshness analysis.Among various chemiresistive sensing materials,noble metal-decorated semiconducting metal oxides(SMOs)have currently aroused extensive attention by virtue of the unique electronic and catalytic properties of noble metals.This review highlights the research progress on the designs and applications of different noble metal-decorated SMOs with diverse nanostructures(e.g.,nanoparticles,nanowires,nanorods,nanosheets,nanoflowers,and microspheres)for high-performance gas sensors with higher response,faster response/recovery speed,lower operating temperature,and ultra-low detection limits.The key topics include Pt,Pd,Au,other noble metals(e.g.,Ag,Ru,and Rh.),and bimetals-decorated SMOs containing ZnO,SnO_(2),WO_(3),other SMOs(e.g.,In_(2)O_(3),Fe_(2)O_(3),and CuO),and heterostructured SMOs.In addition to conventional devices,the innovative applications like photo-assisted room temperature gas sensors and mechanically flexible smart wearable devices are also discussed.Moreover,the relevant mechanisms for the sensing performance improvement caused by noble metal decoration,including the electronic sensitization effect and the chemical sensitization effect,have also been summarized in detail.Finally,major challenges and future perspectives towards noble metal-decorated SMOs-based chemiresistive gas sensors are proposed.

Finned Zn-MFI zeolite encapsulated noble metal nanoparticle catalysts for the oxidative dehydrogenation of propane with carbon dioxide

Oxidative dehydrogenation of propane with carbon dioxide(CO_(2)-ODP)characterizes the tandem dehydrogenation of propane to propylene with the reduction of the greenhouse gas of CO_(2)to valuable CO.However,the existing catalyst is limited due to the poor activity and stability,which hinders its industrialization.Herein,we design the finned Zn-MFI zeolite encapsulated noble metal nanoparticles(NPs)as bifunctional catalysts(NPs@Zn-MFI)for CO_(2)-ODP.Characterization results reveal that the Zn2+species are coordinated with the MFI zeolite matrix as isolated cations and the NPs of Pt,Rh,or Rh Pt are highly dispersed in the zeolite crystals.The isolated Zn2+cations are very effective for activating the propane and the small NPs are favorable for activating the CO_(2),which synergistically promote the selective transformation of propane and CO_(2)to propylene and CO.As a result,the optimal 0.25%Rh0.50%Pt@Zn-MFI catalyst shows the best propylene yield,satisfactory CO_(2)conversion,and long-term stability.Moreover,considering the tunable synergetic effects between the isolated cations and NPs,the developed approach offers a general guideline to design more efficient CO_(2)-ODP catalysts,which is validated by the improved performance of the bifunctional catalysts via simply substituting Sn4+cations for Zn2+cations in the MFI zeolite matrix.

Towards the selectivity distinction of phenol hydrogenation on noble metal catalysts

Selective hydrogenation of phenol to cyclohexanone is intriguing in chemical industry.Though a few catalysts with promising performances have been developed in recent years,the basic principle for catalyst design is still missing owing to the unclear catalytic mechanism.This work tries to unravel the mechanism of phenol hydro-genation and the reasons causing the selectivity discrepancy on noble metal catalysts under mild conditions.Results show that different reaction pathways always firstly converge to the formation of cyclohexanone under mild conditions.The selectivity discrepancy mainly depends on the activity for cyclohexanone sequential hy-drogenation,in which two factors are found to be responsible,i.e.the hydrogenation energy barrier and the competitive chemisorption between phenol and cyclohexanone,if the specific co-catalyzing effect of H 2 O on Ru is not considered.Based on the above results,a quantitative descriptor,E b(one/pl)/E a,in which E a can be further correlated to the d band center of the noble metal catalyst,is proposed by the first time to roughly evaluate and predict the selectivity to cyclohexanone for catalyst screening.

Dielectric barrier discharge plasma synthesis of Ag/γ-Al_(2)O_(3) catalysts for catalytic oxidation of CO

In this study,Ag/γ-Al_(2)O_(3)catalysts were synthesized by an Ar dielectric barrier discharge plasma using silver nitrate as the Ag source andγ-alumina(γ-Al_(2)O_(3))as the support.It is revealed that plasma can reduce silver ions to generate crystalline silver nanoparticles(Ag NPs)of good dispersion and uniformity on the alumina surface,leading to the formation of Ag/γ-Al_(2)O_(3)catalysts in a green manner without traditional chemical reductants.Ag/γ-Al_(2)O_(3)exhibited good catalytic activity and stability in CO oxidation reactions,and the activity increased with increase in the Ag content.For catalysts with more than 2 wt%Ag,100%CO conversion can be achieved at 300°C.The catalytic activity of the Ag/γ-Al_(2)O_(3)catalysts is also closely related to the size of theγ-alumina,where Ag/nano-γ-Al_(2)O_(3)catalysts demonstrate better performance than Ag/micro-γ-Al_(2)O_(3)catalysts with the same Ag content.In addition,the catalytic properties of plasma-generated Ag/nano-γ-Al_(2)O_(3)(Ag/γ-Al_(2)O_(3)-P)catalysts were compared with those of Ag/nano-γ-Al_(2)O_(3)catalysts prepared by the traditional calcination approach(Ag/γ-Al_(2)O_(3)-C),with the plasma-generated samples demonstrating better overall performance.This simple,rapid and green plasma process is considered to be applicable for the synthesis of diverse noble metal-based catalysts.

Fire in the Ceramic Belly

American artist Denis Naymark pursues his ceramic dream in China’s porcelain capital,Jingdezhen.IN the year 1295,on his way back to Europe,Marco Polo could not have imagined that the white“porcellana”he took with him from Jingdezhen would make a big hit,causing a sensation and even a frenzy for porcelain among the Europeans,especially the noblemen.

股骨近段髓腔解剖参数测量与不同类型人工股骨假体的选择

目的对414例股骨近段髓腔解剖特征的X线影像学测量,为临床合理选择股骨假体提供参数。方法随机选择414例苏州大学附属第一医院骨科2005年3月～2008年12月期间股骨近端DR影像资料(DICOM格式),用Dicom viewer软件测量10项股骨近段髓腔径长参数和5项形态参数,分析各参数的特点、相关性及与性别、年龄的关系。结果 (1)年龄因素(女性)和峡部内径显著正相关,随着年龄增长,小粗隆中点下方20 mm处髓腔至峡部髓腔内径变宽大,整个股骨近端髓腔呈宽而直的烟囱型。(2)MCFI集中于1.8～2.4,占总的被测人群68.08%。(3)本组所测CFI,根据Nobel分型,烟囱型髓腔占13.0%,正常型髓腔占72.5%,漏斗型髓腔占14.5%。(4)MCFI和CFI显著正相关,MCFI和DCFI无显著相关性;CFI和DCFI、股骨远端髓腔开大角度显著正相关,CFI和峡部内径显著负相关;DCFI和股骨远端髓腔开大角度显著正相关。结论 (1)股骨近端髓腔形态、大小变异较大,国人之间及与欧美白种人群之间均存在一定的差异。(2)MCFI、CFI、DCFI对描述股骨近端髓腔形态各有侧重,三者结合髓腔径长参数能更准确、细致地刻画髓腔形态。

基于局部熵和方差调整的Noble角点检测算法改进

为了提高角点检测精度,增强算法对伪角点的抑制能力,在Noble算子的基础上充分考虑图像不同区域间灰度统计特性的差异,提出了一种基于局部熵和方差调整的Noble角点检测改进算法.该算法首先选择角点响应函数阈值以及非极大值抑制邻域大小的初始参考值,然后根据区域熵与区域方差分别估计这两个初始参考值的局部调整系数,最后用调整系数对随后的参考值进行加权,获得自适应于真实信号结构的局部阈值以及局部非极大值抑制邻域大小.实验结果表明,所提算法能够精确地检测出大部分真实角点,有效地消除伪角点的干扰.

浮式结构物拖航阻力计算方法探讨

针对某远海大型浮式结构物拖船及拖带设备的选择以及拖航阻力预报问题,提出一种浮式结构物拖航阻力计算方法,根据规范Noble Denton规定的海况条件进行计算,并与船级社CCS提出的经验公式计算结果进行对比,分析表明,经验公式计算结果偏小;风阻力计算必须考虑航速和受风构件的高度系数;波浪阻力对被拖物的影响是不可忽略的;流阻力不能简单采用摩擦阻力和剩余阻力之和进行替代。

导管架滑移下水参数研究与敏感性分析

重量较大的深水导管架一般采用滑移下水、小浮吊辅助扶正的施工方式。下水驳船的尺寸和其初始状态的选择,会影响导管架的下水过程。同时,导管架重量和重心的不确定性、导管架下水滑撑与驳船滑道之间滑动摩擦系数的不确定性、导管架舱室破损以及施工海况都会影响下水分析结果。本文依据Noble Denton规范,对上述参数和敏感性进行了详细研究。文中的研究方法和结论对导管架滑移下水的计算分析和海上施工作业具有一定参考价值。

同步静态随机访问存储器常见问题解析

介绍当今正在大量使用的突发模式SSRAM,零总线反转SSRAM,二倍数据率SSRAM,四倍数据率SSRAM等类器件的差异,澄清一些容易混淆的概念。

高纯氮载气中Kr的简便PVT定量方法

A simple PVT quantitative method of Kr in the high pure N2 was studied. Pressure, volume and temperature of the sample gas were measured by three individual methods to obtain the sum sample with food uncertainty. The ratio of Kr/N2 could be measured by GAM400 quadrupole mass spectrometer. So the quantity of Kr could be calculated with the two measured data above. This method can be suited for quantitative analysis of other simple composed noble gas sample with high pure carrying gas.

孤立心肌桥病人静息心率、左心室结构和收缩功能与Noble分级的关系

目的探讨孤立心肌桥病人静息心率、左心室结构和收缩功能与Noble分级的关系。方法选取2015年—2017年内蒙古自治区巴彦淖尔市医院心内科住院的孤立心肌桥病人111例,按照静息心率水平分为3组,A组41例(静息心率<70次/min)、B组48例(静息心率70~<80次/min)、C组22例(静息心率≥80次/min)。分析影响孤立心肌桥病人心率及Noble分级的因素。结果静息心率与心肌桥Noble分级呈正相关(r=0.612,P=0.000)。左心室射血分数(LVEF)、室间隔厚度(IVST)对静息心率有影响;LVEF、左心室质量(LVM)、左心室质量指数(LVMI)对Noble分级有影响(均P<0.05)。结论孤立心肌桥病人静息心率与心肌桥Noble分级呈正相关,可通过不同水平静息心率与LVEF、LVM、LVMI评估心肌桥Noble分级情况。

动物的领域

领域(Territoriality)是动物学常用术语之一。但是在应用这一概念时却有很大差别,这里我们引用Noble’s(1939a)定义:任何被该动物保卫的区域称之该动物的领域。这个地区的保卫包括直接攻击、威吓;也包括声音恐吓以及一些特殊姿态使入侵者逃走。一些发情的雄鸟,在一定区域不能忍受其他个体侵入,有明显地保护区域的现象,这个现象的研究导致提出了领域,到1868年Altum在“Der vogel und seinleben”提出了领域这个概念。1920年El-iot Howar在他的著作中“鸟类生活中的领域”(Territory in Bird life)才精辟地阐明领域现象。

翻译者,叛徒乎?

译事之难,如履薄冰,大凡翻译,必有所失,故有意大利名句“Traduttori traditori”云云。新近出版的《英语外来语词典》(沈叙伦编译,北京语言学院出版社,1990年4月第一版)将此名句汉译为:“翻译是叛徒”。笔者对此存有异议。 查Dizionario della Lingua Italiana(《意大利语词典》,P.2124), traditore备有两解。其第一义为:tradire il proposito e la fiducia di qlcu.,意即:违背某人意旨或背弃被人信任的人。据《英语外来语词典》说明所述,其编译的主要依据是C.O.Sylvester Mawson编著,Charles Berlitz修订的Dictionary of Foreign Terms(Barnes & Noble Books,Second Edition)。

Noble型分块态射的Moore-Penrose逆

讨论了加法范畴中Noble型分块态射m=[acbd]的Moore-Penrose逆,且给出了Moore-Penrose逆的表达式.

父亲的座右铭

The teacher was giving her class a lecture on m ottoes,and remarked that she wished the class to memorize the motto,＂It is better to give than to receive.＂A small boy cried out,＂Yes,Miss,my father say she has always used that as his motto in business.＂＂Oh,how noble of him!What is his business？＂