Critical role of carbon support in metal nanoaggregate facilitating Fe-N-C catalyst for PEM fuel cell application

Metal nanoaggregates can simultaneously enhance the activity and stability of Fe-N-C catalysts in proton-exchange-membrane fuel cells(PEMFC).Previous studies on the relevant mechanism have focused on the direct interaction between FeN_(4)active sites and metal nanoaggregates.However,the role of carbon support that hosts metal nanoaggregates and active sites has been overlooked.Here,a Fe-N-C catalyst encapsulating inactive gold nanoparticles is prepared as a model catalyst to investigate the electronic tuning of Au nanoparticles(NPs)towards the carbon support.Au NPs donate electrons to carbon support,making it rich inπelectrons,which reduces the work function and regulates the electronic configuration of the FeN_(4)sites for an enhanced ORR activity.Meanwhile,the electron-rich carbon support can mitigate the electron depletion of FeN_(4)sites caused by carbon support oxidation,thereby preserving its high activity.The yield and accumulation of H_(2)O_(2)are thus alleviated,which delays the oxidation of the catalyst and benefits the stability.Due to the electron-rich carbon support,the composite catalyst achieves a top-level peak power density of 0.74 W/cm^(2) in a 1.5 bar H_(2)-air PEMFC,as well as the improved stability.This work elucidates the key role of carbon support in the performance enhancement of the FeN-C/metal nanoaggregate composite catalysts for fuel cell application.

负载Ir单原子和团簇的α-MoC催化剂用于高效催化CO_(2)加氢制CO

在高温逆水气变换(RWGS)反应中,开发高活性和高稳定性的金属负载型催化剂还存在巨大挑战。针对此问题,本研究采用溶液蒸发自组装法构建了Ir物种负载于α-Mo C的协同催化剂,结果表明,Ir与α-Mo C的协同效应使其在较宽的温度范围内均有较好的RWGS反应性能。特别是在500℃、0.1 MPa、300000 mL·g^(-1)·h^(-1)的反应条件下,0.5%Ir/MoC催化剂的CO_(2)转化率高达48.4%,接近CO_(2)平衡转化率(49.9%),同时,CO选择性和CO时空收率分别高达94.0%和423.1μmol·g^(-1)·s^(-1),且在100 h之内反应性能几乎没有衰减,具有优异的高温稳定性,此催化性能也超过了大多数文献报道。系列结构表征表明,Ir物种均匀地分散在α-Mo C载体上,其电子较利于转移至α-Mo C而形成金属载体强相互作用,极大地提高了催化稳定性;同时,当Ir负载量高于0.2%(质量分数)时,Ir团簇(Irn)和Ir单原子(Ir1)同时存在,与α-MoC形成了Irn-Ir1-C-Mo协同位点。其中,0.5%Ir/Mo C催化剂拥有较小尺寸的Irn和较多的Ir1,显著地促进了CO_(2)和H2的吸附和活化,并促进了甲酸盐中间体的生成和解离,从而获得了优异的RWGS性能。这项工作为设计和制备高效稳定的CO_(2)利用催化剂提供了一定的参考和指导。

过渡金属催化CO_(2)/H_(2)参与的羰基化研究进展

有限的化石燃料与不断增长的能源需求的矛盾和因温室气体大量排放导致的异常气候变化这两大相关问题引起全世界范围内的关注。二氧化碳(CO_(2))是一种主要的温室气体,同时也是合成燃料和化学品的重要C1资源。利用CO_(2)参与合成化学品能有效减少温室气体的排放。然而,高度氧化、热力学稳定的CO_(2)的化学转化仍然是一较大挑战,需要引入还原剂等参与CO_(2)的化学转化。作为理想的还原剂,氢气(H_(2))可将CO_(2)逆水煤气变换(RWGS)转化为一氧化碳(CO),考虑到有毒CO的繁琐分离和运输,众多研究利用原位生成的CO参与到各种羰基化反应中,既得到了高附加值的化学品,又避免了CO的直接使用。基于此,过渡金属催化CO_(2)/H_(2)参与的羰基化反应得到了广泛地关注和研究,实现了CO_(2)/H_(2)参与的烯烃羰基化生成醇、羧酸、胺、醛等产物。同时多相催化的烯烃羰基化的实现为该领域开发了新的催化体系。在烯烃羰基化的基础上,该领域得到了进一步的发展,CO_(2)参与羰基化的反应路径变得更加丰富,如出现了CO_(2)加氢到甲酸(HCOOH),HCOOH到CO的间接生成CO的路径和CO_(2)直接参与羰基化的反应路径,实现了CO_(2)/H_(2)参与的卤代烃、甲醇(MeOH)及其衍生物等的羰基化反应,获得芳醛、乙酸、乙醇等大宗或精细化学品。CO_(2)/H_(2)参与的羰基化研究的快速发展拓展了CO_(2)资源化利用的途径,获得高附加值的大宗或精细化学品,促进了绿色化学的发展。本文主要围绕过渡金属催化CO_(2)/H_(2)参与的多种羰基化生成高附加值化学品的反应,总结了近年来的研究进展,并对该方向的发展做了展望。

负载型Rh基催化剂上的CO加氢制乙醇反应:载体效应

作为一种重要的基础化学品以及传统能源替代品,乙醇极具应用前景。当前乙醇的生产主要通过谷物发酵和乙烯水合法。然而效率低下的发酵过程和日益枯竭的原油资源限制了乙醇的大规模生产。因此,发展生产乙醇的可替代技术成为重要议题。由合成气(CO+H_(2))出发直接制备乙醇被认为是实现煤炭、天然气和生物质等含碳资源高值化、清洁化利用的新方式。负载型Rh基催化剂作为合成气直接制乙醇最有潜力且最有效的催化体系而受到广泛研究。对于负载型Rh基催化剂来讲,合适的助剂和载体通常可以有效地提升催化剂的活性和乙醇选择性。Fe作为一种提高乙醇选择性最有效的助剂之一而被广泛地应用在Rh基催化剂的研究中。在本文中,为了探究载体的作用,我们利用初湿浸渍法制备出不同载体(CeO_(2)、ZrO_(2)和TiO_(2))负载的Fe促进的Rh基催化剂用于合成气制乙醇反应中。结果表明,RhFe/TiO_(2)催化剂在反应条件为250℃,2 MPa时的CO转化率高达18.2%并且在醇分布中乙醇的选择性高达74.7%,远高于相同条件下RhFe/CeO_(2)和RhFe/ZrO_(2)催化剂的性能。表征结果表明,催化剂的比表面从小到大依次为RhFe/CeO_(2)<RhFe/ZrO_(2)<RhFe/TiO_(2),而Rh的分散度也依次增加、粒径依次减小。这是由于较大的比表面积可能有利于Rh物种的分散,高分散的Rh物种就意味着存在更多的活性位点。H_(2)-程序升温还原结果表明Rh与载体、Rh与Fe之间存在相互作用,并且在实验的还原条件下TiO_(2)会发生部分还原,而其它的载体则不会发生还原。X射线光电子能谱分析结果表明RhFe/TiO_(2)催化剂具有更多的乙醇生成(Rh_(x)^(0)-Rh_(y)^(+))-O-Fe^(δ+)活性位点,使得乙醇的选择性增加。CO-程序升温脱附被用来确认不同催化剂的CO吸附能力,结果表明TiO_(2)由于存在更多的O空穴和Ti^(3+)离子从而增强了对CO的吸附,因此有利于催化剂活性的提高。

以类水滑石为前驱体的Cu/ZnO/Al_(2)O_(3)催化剂用于CO_(x)加氢合成甲醇:CO在反应混合物中的作用

近年来,催化CO_(2)加氢合成甲醇被视为有望解决温室效应和燃料枯竭的有效途径。目前,铜基催化剂因具有较高的反应活性被广泛应用于工业生产。然而,竞争逆水煤气变换反应产生的CO导致甲醇选择性较低,同时副产物水引起Cu发生不可逆烧结,进而降低甲醇产率。众所周知,CO能够调整分子的表面竞争吸附和活性位的氧化还原行为,本工作拟向原料气中掺入具有还原性的CO以抑制逆水煤气变换反应和防止表面氧化中毒。另一方面,通常认为铜基催化的CO_(2)加氢制甲醇是结构敏感性反应,不同的前驱体能够显著影响催化剂结构和形貌,进而影响催化活性。因此,我们首先通过共沉淀法和蒸氨法制备了含有类水滑石前驱体(CHT-CZA)和复合物前驱体(CNP-CZA)结构的Cu/ZnO/Al_(2)O_(3)催化剂。随后,为探究CO掺杂后反应机理,在250℃,5 MPa的反应条件下,含有不同比例CO的原料气中(CO_(2):CO:H_(2):N_(2)=x:(24.5−x):72.5:3)评价两种催化剂对甲醇合成的性能。评价结果显示两种催化剂反应性能趋势相同,随着CO含量增加,CO_(2)转化率和STY_(H2O)不断降低,STY_(MeOH)逐渐增加。X射线光谱(XPS)显示随CO含量增加,催化剂表面还原性Cu比例增加。评价和表征结果说明CO引入抑制了逆水煤气变换反应的发生,通过还原被H_(2)O氧化的活性Cu表面,促使更多的活性Cu位点暴露参与甲醇合成。另一方面,透射电镜(TEM)显示掺杂的CO会过度还原而引起颗粒团聚,导致催化剂逐渐失活。相比之下,含有水滑石前驱体的催化剂在任何气氛下均表现出更加优越的反应性能和长周期稳定性。这可归因于类水滑石前驱体独特的片层结构通过结构限域作用有效避免了因CO过度还原而导致的金属颗粒团聚,从而减少活性位点损失。

金二元纳米晶超晶格的自组装和结构表征

将双组分纳米晶(例如金属、磁体和半导体)混合物组装成二元纳米晶超晶格为构建新型材料提供了一条新的途径。二元纳米晶超晶格不仅具有有趣的结构,还表现出了其构建单元的复合以及集体的性能,因此被广泛应用于电磁器件领域。然而大多数的研究主要集中在不同尺寸的双组分纳米晶自组装成的二元纳米晶超晶格。很少有报道研究不同尺寸单组分纳米晶,尤其是金纳米晶构筑的二元纳米晶超晶格。因此,发展一种简单有效的方法构建不同尺寸的单组分二元纳米晶超晶格具有重要意义。本文以十二烷硫醇稳定的3.7 nm金纳米晶为种子,在油胺中,采用种子生长法合成了6.0、7.3和9.6 nm的单分散金纳米晶。将油胺修饰的6.0、7.3和9.6 nm金纳米晶分别与3.7 nm金纳米晶以一定浓度比混合。采用溶剂蒸发法制备了AB2型(六边形AlB2结构),AB13型(NaZn13结构)和AB型(立方NaCl结构)的金二元纳米晶超晶格。本实验结果与相关的空间填充原理非常吻合。研究以单组分作为构建单元构筑的二元纳米晶超晶格结构与性能以及新型超材料的潜在发展具有重要意义。

Environmentally Tough and Stretchable MXene Organohydrogel with Exceptionally Enhanced Electromagnetic Interference Shielding Performances

Conductive hydrogels have potential applications in shielding electromagnetic(EM)radiation interference in deformable and wearable electronic devices,but usually suffer from poor environmental stability and stretching-induced shielding performance degradation.Although organohydrogels can improve the environmental stability of materials,their development is at the expense of reducing electrical conductivity and thus weakening EM interference shielding ability.Here,a MXene organohydrogel is prepared which is composed of MXene network for electron conduction,binary solvent channels for ion conduction,and abundant solvent-polymer-MXene interfaces for EM wave scattering.This organohydrogel possesses excellent anti-drying ability,low-temperature tolerance,stretchability,shape adaptability,adhesion and rapid self-healing ability.Two effective strategies have been proposed to solve the problems of current organohydrogel shielding materials.By reasonably controlling the MXene content and the glycerol-water ratio in the gel,MXene organohydrogel can exhibit exceptionally enhanced EM interference shielding performances compared to MXene hydrogel due to the increased physical cross-linking density of the gel.Moreover,MXene organohydrogel shows attractive stretching-enhanced interference effectiveness,caused by the connection and parallel arrangement of MXene nanosheets.This well-designed MXene organohydrogel has potential applications in shielding EM interference in deformable and wearable electronic devices.

Efficient catalytic conversion of carbohydrates into 5-ethoxymethylfurfural over MIL-101-based sulfated porous coordination polymers

In this work, a series of MIL-101-SO3H（x） polymeric materials were prepared and further used for the first time as efficient heterogeneous catalysts for the conversion of fructose-based carbohydrates into 5-ethoxymethylfurfural（EMF） in a renewable mixed solvent system consisting of ethanol and tetrahydrofuran（THF）. The influence of –SO3H content on the acidity as well as on the catalytic activity of the porous coordination polymers in EMF production was also studied. High EMF yields of 67.7% and 54.2% could be successively obtained from fructose and inulin in the presence of MIL-101-SO;H（100） at 130 °C for 15 h.The catalyst could be reused for five times without significant loss of its activity and the recovery process was facile and simple. This work provides a new platform by application of porous coordination polymers（PCPs） for the production of the potential liquid fuel molecule EMF from biomass in a sustainable solvent system.

Heterosis for water uptake by maize (Zea mays L.) roots under water deficit: responses at cellular, single-root and whole-root system levels

To examine the potential heterosis for water uptake by maize roots, the hydraulic properties of roots in the F1 hybrid （Hudan 4） were compared with those of its inbred parents （ 478 and Tian 4） at cellular, single-root and whole-root system levels under well-watered and water-deficit conditions. The cell hydraulic conductivity （Lpc） decreased under water deficit, but the Lpc of the F1 was higher than that of its inbred parents with or without stress from water deficit. Marked reductions in Lpc were observed following Hg2＋ treatment. The hydrostatic hydraulic conductivity of single roots （hydrostatic Lpsr） varied among genotypes under the two water treatments, with the highest in the F1 and the lowest in 478. Radial hydraulic conductivity （radial Lpsr） and axial hydraulic conductance （Lax） of the three genotypes varied similarly as Lpsr. The variations in hydraulic parameters were related to root anatomy. Radial Lpsr was negatively correlated with the ratio of cortex width to root diameter （R2=-0.77, P〈0.01）, whereas Lax was positively correlated with the diameter of the central xylem vessel （R2=0.75, P〈0.01） and the cross-sectional area of xylem vessels （R2=0.93, P〈0.01 ）. Hydraulic conductivity （Lpwr） and conductance （Lwr） of the whole-root system followed the same trend under the two water treatments, with the highest values in the F1. The results demonstrated that heterosis for water uptake by roots of the F1 occurred at cellular, single-root and whole-root system levels under well-watered and water-deficit conditions.

The study on DNA methylation of p53-Bax mitochondrial apoptosis pathway in cholangiocarcinoma

Objective： To study the methylation status of several genes on p53-Bax mitochondrial apoptosis pathway and clinical significance in cholangiocarcinoma. Methods： Promoter hypermethylation of DAPK, p14 and ASC genes were detected by methylation-specific PCR. p53 gene status （exon 5-8） were examined by automated sequencing, combined with the clinical documents of patients by statistics analysis. Results： （1） We found 66.7% of 36 cases cholangiocarcinoma had methylation of at least one tumor suppressor gene. The frequency of tumor suppressor gene methylation in cholangiocarcinoma was： p14 （24%）, DAPK （30.6%）, TMSI/ASC （36.1%）. The frequency of tumor suppressor gene methylation in tissues near cancer was： DAPK （5.6%）, TMS1/ASC （8.3%）. （2） p53 gene mutations were found in 22 of 36 patients （61.1%）. （3） There were no statistically relationship among the methylation of DAPK, p14 and ASC genes. There were negative relationship differences between the methylation of p14 and p53 gene mutation （P 〈 0.05）. （4） p53 gene mutation combined with the methylation of tumor suppressor were 14 cases （38.9%）. There were statistically differences on extent of pathologic biology, differentiation and invasion （P 〈 0.05）. Conclusion： Our study indicated that methylation of p53-Bax mitochondrial apoptosis pathway in cholangiocarcinoma was a common epigenetic event. Although the methylation of ASC, DAPK genes was low, it might be significance for early diagnosis, p53 gene mutation combined with the methylation of tumor suppressor might be relationship with pathologic biology, it trended to more malignancy.

Oriented magnetic liquid metal-filled interlocked bilayer films as multifunctional smart electromagnetic devices

Smart electromagnetic functional devices prepared based on electromagnetic wave responsive materials will provide more convenience for human life in the future.Here,we prepare oriented magnetic liquid metal droplet-filled polydimethylsiloxane films with micropillar array patterned surfaces,and further assemble them into bilayer films with interlocked structures.Once compressed,the increase in conductivity of the film due to the tunneling effect between microarrays and the elongation of liquid metal droplets leads to a rapid increase in electromagnetic interference shielding performance.Accordingly,a tunable electromagnetic interference shielding material with high sensitivity and wide control range is obtained,which has potential applications in electromagnetic wave control systems and intelligent electromagnetic protection systems.Meanwhile,we assemble a strain sensor and a magnetic sensor,which can precisely sense pressure and magnetic field according to changes in electromagnetic signal and electrical signal,respectively.

亚微米去顶角八面体LiNi_(0.08)Mn_(1.92)O_(4)正极材料制备及高温电化学性能

采用低温固相燃烧法快速制备了一种具有{111}、{110}和{100}晶面的去顶角八面体LiNi_(0.08)Mn_(1.92)O_(4)(LNMO)正极材料,其高暴露{111}晶面可以减少充放电过程中Mn的溶解,面积相对较小的{110}和{100}晶面可增加Li^(+)快速扩散的通道.测试结果表明,所合成的LNMO具有LiMn_(2)O_(4)特有的立方晶系结构,其颗粒尺寸为亚微米级.LNMO的高温电化学性能优异,在55℃,1和5 C的首次放电比容量分别为109.9和98.0 m Ah/g,分别循环300次后容量保持率为75.8%和80.5%;即使在55℃,10和15 C下分别循环1000次后仍具有48.4%和49.4%的容量保持率,而未掺杂的LiMn_(2)O_(4)于15 C循环1000次后容量损失高达98%.LNMO在55℃有较高的Li^(+)扩散系数(D=3.86×10^(-15)cm^(2)/s)和较小的电荷转移阻抗(循环前、后R_(ct)=158.0和279.8Ω)以及较低的表观活化能(E_(a)=17.63 k J/mol),说明Ni掺杂能够提高Li^(+)在尖晶石型LiMn_(2)O_(4)内的扩散速率及减小锂离子在脱嵌过程中的能垒,从而提高锂离子的扩散速率和倍率性能.对LNMO于55℃循环1000次后的极片进行X射线衍射(XRD)分析,发现LNMO电极材料的晶体结构基本保持不变,表明Ni掺杂提高了锰酸锂材料在55℃长循环过程中的晶体结构稳定性,有效抑制了Jahn-Teller效应及Mn的溶解,显著提升了其高温电化学性能.本工作为尖晶石LiMn_(2)O_(4)电极材料在高温方面的应用提供了借鉴.

Yolk-shell structured Co-C/Void/Co9S8 composites with a tunable cavity for ultrabroadband and efficient low- frequency microwave absorption

A yolk-shell structured Co-C/Void/CogS8 ternary composite composed of a Co nanoparticle-embedded porous carbon core and Co9S8 shell was synthesized by the sulfidation of a Co-based zeolitic imidazolate framework and subsequent pyrolysis. The composition and interior cavity of the Co-C/Void/CogS8 composite could be precisely modulated by controlling the sulfidation reaction. Due to the abundant heterointerfaces, well-controlled cavity, and magnetic-dielectric synergistic effects, the Co-C/Void/CogS8 exhibited excellent and tunable microwave- absorbing properties. The optimized Co-C/Void/Cog~ having a loading of 25 wt.% and thickness only 2.2 mm, displayed an ultrabroad absorption bandwidth of 8.2 GHz at high frequencies. Moreover, the composite could achieve an extremely high reflection loss of -54.02 dB at low frequencies by adjusting its loading to 30 wt.%. This study provides a new insight into promising lightweight microwave-absorbing materials with ultrabroad absorption bandwidths and strong low-frequency absorption.

Synergy between metallic components of MoNi alloy for catalyzing highly efficient hydrogen storage of MgH2

Catalysts play a critical role in improving the hydrogen storage kinetics in Mg/MgH2 system.Exploring highly efficient catalysts and catalyst design principles are hot topics but challenging.The catalytic activity of metallic elements on dehydrogenation kinetics generally follows a sequence of Ti>Nb>Ni>V>Co>Mo.Herein,we report a highly efficient alloy catalyst composed of low-active elements of Mo and Ni(i.e.MoNi alloy)for MgH2 particles.MoNi alloy nanoparticles show excellent catalytic effect,even outperforming most advanced Ti-based catalysts.The synergy between Mo and Ni elements can promote the break of Mg-H bonds and the dissociation of hydrogen molecules,thus significantly improves the kinetics of Mg/MgH2 system.The MoNi-catalyzed Mg/MgH2 system can absorb and release 6.7 wt.%hydrogen within 60 s and 10 min at 300℃,respectively,and exhibits excellent cycling stability and low-temperature hydrogen storage performance.This study provides a strategy for designing efficient catalysts for hydrogen storage materials using the synergy of metal elements.

Effects of Y and Zn additions on electrical conductivity and electromagnetic shielding effectiveness of Mg-Y-Zn alloys

Microstructure, electrical conductivity, and electromagnetic interference(EMI) shielding effectiveness(SE) of cast Mg-x Zn-y Y(x = 2–5, y = 1–10) alloys were systematically investigated to understand the effects of Zn and Y additions on electrical conductivity and electromagnetic shielding effectiveness of the alloys.Experimental results indicate that the electrical conductivity and SE of the Mg-x Zn-y Y alloys decrease with Y/Zn ratio. Electrical conductivity is the main factor that affects the electromagnetic shielding properties and the variation tendency of electromagnetic shielding properties of the Mg-x Zn-y Y alloys is consistent with conductivity. Valence of Y and Zn atoms, configuration of extranuclear electron and volumetric difference are main reasons for the variations in the electrical conductivity. A high density of second phase and the formation of semi-continuous network structure can also improve the SE value at high frequencies.

Catalysis stability enhancement of Fe/Co dual-atom site via phosphorus coordination for proton exchange membrane fuel cell

Non-precious metal catalysts(NPMCs)are promising low-cost alternatives of Pt/C for oxygen reduction reaction(ORR),which however suffer from serious stability challenge in the devices of proton-exchange-membrane fuel cells(PEMFC).Different from the traditional strategies of increasing the degree of graphitization of carbon substrates and using less Fenton-reactive metals,we prove here that proper regulation of coordination anions is also an effective way to improve the stability of NPMC.N/P cocoordinated Fe-Co dual-atomic-sites are constructed on ZIF-8 derived carbon support using a molecular precursor of C_(34)H_(28)Cl_(2)CoFeP_(2)and a“precursor-preselected”method.A composition of FeCoN_(5)P1 is infered for the dual-atom active site by microscopy and spectroscopy analysis.By comparing with N-coordinated references,we investigate the effect of P-coodination on the ORR catalysis of Fe-Co dual-atom catalysts in PEMFC.The metals in FeCoN_(5)P1 have the lower formation energy than those in the solo N-coordinated active sites of FeCoN6 and FeN_(4),and exhibits a much better fuel cell stability.This anion approach provides a new way to improve the stability of dual-atom catalysts.

Boosting electrocatalytic water splitting via metal-metalloid combined modulation in quaternary Ni-Fe-P-B amorphous compound

Design and synthesis of highly efficient and cost-effective bifunctional catalysts for hydrogen evolution reaction(HER)and oxygen evolution reaction(OER)remain a big challenge.Herein,a quaternary amorphous nanocompound Ni-Fe-P-B has been synthesized by a facile,scalable co-reduction method.The Ni-Fe-P-B exhibits high electrocatalytic activity and outstanding durability for both HER and OER,delivering a current density of 10 mA·cm^-2 at overpotentials of 220 and 269 mV,respectively.When loaded on carbon fiber paper(CFP)as a bifunctional catalyst,the Ni-Fe-P-B@CFP electrode requires a low cell voltage of 1.58 V to obtain 10 mA·cm^-2 for overall water splitting with negligible recession over 60 h.The excellent catalytic performances of Ni-Fe-P-B mainly benefit from the metal-metalloid combined composition modulation and the unique amorphous structure.This work provides new insights into the design of robust bifunctional catalysts for water splitting,and may promote the development of multicomponent amorphous catalysts.

Significantly enhanced piezo-photocatalytic capability in BaTiO_(3) nanowires for degrading organic dye

Over the last several years,piezo-photocatalytic effect was intensively investigated for a facile,effective and promising protocol to sewage treatment and environmental remediation.The research on the integration of piezocatalytic and photocatalytic process on lead-free ferroelectric materials is highly demanded to further push this field forward.In this work,BaTiO_(3) nanowires(BT NWs)were fabricated by a two-step hydrothermal method.The degradation of organic dye(methyl orange,MO)aqueous solution(5 mg L^(-1))by integrating photocatalysis with the piezoelectric-like effect under UV light radiation and ultrasonic vibration was investigated.The decomposition ratio reaches up to ~98.17%(at 80 min),which is around 1.28 and 2.24 times of the sole piezocatalysis and photocatalysis process,respectively.The intermediate product of hydroxyl radical(·OH)and superoxide radical(·O_(2)^(-))was detected and quantified by radical trapping experiments,to illustrating their key role in degrading MO molecules.In addition,we carried out sequential cycles to evaluate the cycling stability and usage durability of catalysts and a reduction of ~15% in the efficiency was observed after four cycles.This work provides a promising paradigm for the further development of piezo-photocatalytic materials and target applications in environmental field.

Mathematical Analysis on the Uniqueness of Reverse Algorithm for Measuring Elastic-plastic Properties by Sharp Indentation

The reverse analysis provides a convenient method to determine four elastic-plastic parameters through an indentation curve such as Young s modulus E, hardness H, yield strength σy and strain hardening exponent n. In this paper, mathematical analysis on a reverse algorithm from Dao model （Dao et al., Acta Mater., 2001, 49, 3899） was carried out, which thought that only when 20 ≤E＊/σ0.033≤ 26 and 0.3n≤ 0.5, the reverse algorithm would yield two solutions of n by dimensionless function Π2. It is shown that, however, there are also two solutions of n when 20≤E＊/σ0.033≤ 26 and 0≤n0.1. A unique n can be obtained by dimensionless function Π3 instead of Π2 in these two ranges. E and H can be uniquely determined by a full indentation curve, and σy can be determined if n is unique. Furthermore, sensitivity analysis on obtaining n from dimensionless function Π3 or Π2 has been made.

Cesium lead halide perovskite nanocrystals for ultraviolet and blue light blocking

Using cesium lead halide perovskite nanocrystals, CsPb(Cl/Br)3, as a light absorber, we report a highly effective UV and blue light blocking film. The CsPb(Cl/Br)3 nanocrystals are well dispersed in the ethyl cellulose(EC) matrix to compose a UV and blue light shielding film, and the absorption edge of the film is tunable by adjusting Cl to Br ratio using anion exchange. The CsPbCl2 Br-EC film exhibits a transmittance of 5% at 459 nm, 90% at 478 nm and 95% in the range of 500–800 nm, which makes it excellent for UV and blue light shielding. In addition, the as-prepared EC-CsPb(Cl/Br)3 film shows excellent photostability under UV irradiation. Results demonstrate that this EC-CsPb(Cl/Br)3 based materials with sharp absorbance edges, tunable blocking wavelength, and high photostability can be useful for the applications in UV and blue light blocking and optical filters.