Significant progress has been made in the development of non-precious metal electrocatalysts （NPMEs） during the past decade. Correspondingly, there is an urgent demand for an appropriate measurement method to be est...Significant progress has been made in the development of non-precious metal electrocatalysts （NPMEs） during the past decade. Correspondingly, there is an urgent demand for an appropriate measurement method to be established for the reliable evaluation of NPMEs. In this study, platinum and graphite counter electrodes were used to investigate the impact of counter electrode material on the accelerated durability testing （ADT） of NPMEs in acidic medium. Platinum used as the coun- ter electrode in a traditional three-electrode electrochemical cell was found to dissolve in acidic medium and re-deposit on NPME coated on the working electrode during ADT. Such re-deposition causes the oxygen reduction reaction （ORR） performance of NPMEs to remarkably improve, and thus will seriously mislead our judgment of NPMEs if we are unaware of it. The phenomenon can be avoided using a graphite counter electrode.展开更多
The fabrication of a pyrocarbon coated carbon paper and its application to the gas diffusion lay(GDL) of proton exchange membrane(PEM) fuel cell were described.This carbon paper was fabricated by using conventional ca...The fabrication of a pyrocarbon coated carbon paper and its application to the gas diffusion lay(GDL) of proton exchange membrane(PEM) fuel cell were described.This carbon paper was fabricated by using conventional carbon paper as the precursor,and coating it with pyrocarbon by pyrolyzing propylene via the chemical vapor deposition(CVD) method.For comparison,conventional carbon paper composites were also prepared by using PAN-based carbon fiber felt as the precursor followed by impregnation with resin,molding and heat-treatment.SEM characterization indicates that pyrocarbon is uniformly deposited on the surface of the fiber in the pyrocarbon coated carbon paper and made the fibers of carbon felt bind more tightly.In contrast,there are cracks in matrix and debonding of fibers due to carbonization shrinkage in the conventional carbon paper.Property measurements show that the former has much better conductivity and gas permeability than the latter.In addition,current density-voltage performance tests also reveal that the pyrocarbon coating can improve the properties of carbon paper used for electrode materials of fuel cell.展开更多
This paper presents a straightforward model studying the performance of a solid oxide electrolysis cell at less computational effort while is still comprehensive accounting for details of all physics involved. The mod...This paper presents a straightforward model studying the performance of a solid oxide electrolysis cell at less computational effort while is still comprehensive accounting for details of all physics involved. The model is one dimensional and can be used to optimize SOECs that have composite electrodes. It includes an average mass transfer analysis used to simulate concentration polarization, activation polarization, as well as ohmic loss. The electrochemical reaction that occurs within the electrode functional layers has been accounted for in the calculation of the concentration polarization. This is believed to give a more realistic view of the mass transfer that occurs in SOECs with composite electrodes via a simple and straightforward one dimensional model. Experimental work with SOECs also has been done and some results are reported. The simulation results are compared with experimental data and the agreement is satisfactory. The model can be conveniently used for optimization of the SOEC electrodes and operational conditions.展开更多
Due to important consideration of protection against lightning surge on electrical, electronic and telecommunication equipment, it was necessary to carry out a special study to look at the performance of protective de...Due to important consideration of protection against lightning surge on electrical, electronic and telecommunication equipment, it was necessary to carry out a special study to look at the performance of protective devices. The study was testing performance of arresters on low voltage system. The activity was testing of arresters using steady state and impulse voltages. The arresters consisted of gas tube, zener diode, varistor and spark gap arresters, then it was made a cascade circuit between the varistor and spark gap arresters with a decoupling element. The decoupling elements were used air, iron and ferrite. The test yielded data of current and voltage on the tables and oscilloscope waveforms. The arresters had cut voltages early different from each other, namely the gas tube, zener diode, spark gap and varistor arresters were at the voltages of 500 V, 250 V, 1,000 V and 565 V respectively. The iron core decoupling element cascade circuit had the least oscillation among remaining cores.展开更多
As a promising anode material candidate for sodium-ion batteries,antimony(Sb)has attracted enormous research interest due to its high specific capacity and low sodiation voltage.However,its dramatic volume expansion u...As a promising anode material candidate for sodium-ion batteries,antimony(Sb)has attracted enormous research interest due to its high specific capacity and low sodiation voltage.However,its dramatic volume expansion upon sodiation adversely affects its cycle stability.We have developed an oxidation-coating-reduction strategy for fabricating yolk-shell Sb@C rods from commercially available Sb powder.In particular,the thermal reduction of vaporized Sb_(2)O_(3) generates densely distributed Sb single atoms and clusters on the carbon shell.The sodiation process of the Sb@C sample was recorded through in situ transmission electron microscopy.Irregular expansion of Sb particles was observed,and it was also revealed that the carbon shell could deform with the expanded Sb particles.Beyond the intuitively understood advantage that internal voids can provide space for expansion of internal active materials,the deformability of carbon shells can add further ability to withstand the volume expansion.The two structural merits of the yolk-shell construction enable the Sb@C material to deliver an enhanced cycle performance.Its reversible capacity exceeds 620 mA h g^(−1) at 0.1C,with an initial coulombic efficiency of up to 84.9%,and about 95%of the capacity in the charging voltage profile is delivered below 1.0 V vs.Na+/Na.These performance metrics are very promising for potential practical applications.展开更多
Flexible pressure sensors have attracted great attention due to their potential in the wearable devices market and in particular in human-machine interactive interfaces.Pressure sensors with high sensitivity,wide meas...Flexible pressure sensors have attracted great attention due to their potential in the wearable devices market and in particular in human-machine interactive interfaces.Pressure sensors with high sensitivity,wide measurement range,and low-cost are now highly desired for such practical applications.In the present investigation,an ultrasensitive pressure sensor with wide measurement range has been successfully fabricated.Carbon nanotubes(CNTs)(uniformly sprayed on the surface of paper)comprise the sensitivity material,while lithographed interdigital electrodes comprise the substrate.Due to the synergistic effects of CNT’s high specific surface area,paper’s porous structure,interdigital electrodes’efficient contact with CNT,our pressure sensor realizes a wide measurement range from 0 to 140 kPa and exhibits excellent stability through 15,000 cycles of testing.For the paper-based CNT film/interdigitated structure(PCI)pressure sensor,the connection area between the sensitive material and interdigital electrodes dominates in the lowpressure region,while internal change within the sensitive materials plays the leading role in the high-pressure region.Additionally,the PCI pressure sensor not only displays a high sensitivity of 2.72 kPa–1(up to 35 kPa)but also can detect low pressures,such as that exerted by a resting mung bean(about 8 Pa).When attached to the surface of a human body,the pressure sensor can monitor physiological signals,such as wrist movement,pulse beats,or movement of throat muscles.Furthermore,the pressure sensor array can identify the spatial pressure distribution,with promising applications in humanmachine interactive interfaces.展开更多
基金supported by Singapore Ministry of Education Ac RF Tier 2 (MOE2019-T2-2-105), Ac RF Tier 1 RG4/17 and RG161/19。
文摘二维(2D)过渡金属氧化物(TMO)的地球丰度高,并且具有独特的物理化学性质和较好的催化性能,是新能源工业领域中非常有应用前景的电催化剂.然而,由于合成高质量和可控厚度的2D TMO具有一定的难度,目前有关2D TMO的微观电化学研究的报道较少.本文采用化学气相沉积法直接合成了2D钴铁氧体(CoFeO),所制得的2D CoFeO呈现结晶性良好的超薄尖晶石结构,其最薄厚度可达到6.8 nm.采用超微电极测试平台考察了碱性条件下2DCoFeO催化析氧反应(OER)的性能.结果表明,2D CoFeO(111)面在10 m Acm^(-2)的电流密度下表现出330 m V的低过电位,在570 m V的过电位下表现出142 m Acm^(-2)的高电流密度.密度泛函理论计算发现2DCoFeO表面上的双金属位点降低了反应能垒.此外,2DCoFeO的超薄厚度使体电阻率降低,同时增加了活性位点的利用率,进而提高了对OER的催化活性,这与在超微电极平台上测得的2D CoFeO厚度-OER活性依赖关系的结果一致.本研究还合成了大面积的2D CoFeO薄膜,其标准三电极体系研究表明2D CoFeO样品仍然表现出较高的催化OER活性和较好的寿命,说明所制备的2D CoFeO具有较好的实际应用潜力.综上,本文采用气相化学沉积法直接合成了超薄2DCoFeO纳米片,其最薄厚度可达6.8 nm,2DCoFeO表现出良好的OER性能,为2DTMOs电催化剂的可控合成开辟了新途径.此外,本文还分析了2DCoFeO电催化OER反应的机理,为二维电催化剂设计提供了新思路.
基金supported by the Fundamental Research Funds for the Central Universities(DUT15RC(3)001,DUT15ZD225)the Program for Liao-ning Excellent Talents in University(LR2015014)+1 种基金the Liaoning BaiQianWan Talents Program(201519)Dalian Excellent Young Scientific and Technological Talents(2015R006)
文摘Significant progress has been made in the development of non-precious metal electrocatalysts （NPMEs） during the past decade. Correspondingly, there is an urgent demand for an appropriate measurement method to be established for the reliable evaluation of NPMEs. In this study, platinum and graphite counter electrodes were used to investigate the impact of counter electrode material on the accelerated durability testing （ADT） of NPMEs in acidic medium. Platinum used as the coun- ter electrode in a traditional three-electrode electrochemical cell was found to dissolve in acidic medium and re-deposit on NPME coated on the working electrode during ADT. Such re-deposition causes the oxygen reduction reaction （ORR） performance of NPMEs to remarkably improve, and thus will seriously mislead our judgment of NPMEs if we are unaware of it. The phenomenon can be avoided using a graphite counter electrode.
基金Project(50772134) supported by the National Natural Science Foundation of ChinaProject(2006CB600901) supported by the National Basic Research Program of China
文摘The fabrication of a pyrocarbon coated carbon paper and its application to the gas diffusion lay(GDL) of proton exchange membrane(PEM) fuel cell were described.This carbon paper was fabricated by using conventional carbon paper as the precursor,and coating it with pyrocarbon by pyrolyzing propylene via the chemical vapor deposition(CVD) method.For comparison,conventional carbon paper composites were also prepared by using PAN-based carbon fiber felt as the precursor followed by impregnation with resin,molding and heat-treatment.SEM characterization indicates that pyrocarbon is uniformly deposited on the surface of the fiber in the pyrocarbon coated carbon paper and made the fibers of carbon felt bind more tightly.In contrast,there are cracks in matrix and debonding of fibers due to carbonization shrinkage in the conventional carbon paper.Property measurements show that the former has much better conductivity and gas permeability than the latter.In addition,current density-voltage performance tests also reveal that the pyrocarbon coating can improve the properties of carbon paper used for electrode materials of fuel cell.
文摘This paper presents a straightforward model studying the performance of a solid oxide electrolysis cell at less computational effort while is still comprehensive accounting for details of all physics involved. The model is one dimensional and can be used to optimize SOECs that have composite electrodes. It includes an average mass transfer analysis used to simulate concentration polarization, activation polarization, as well as ohmic loss. The electrochemical reaction that occurs within the electrode functional layers has been accounted for in the calculation of the concentration polarization. This is believed to give a more realistic view of the mass transfer that occurs in SOECs with composite electrodes via a simple and straightforward one dimensional model. Experimental work with SOECs also has been done and some results are reported. The simulation results are compared with experimental data and the agreement is satisfactory. The model can be conveniently used for optimization of the SOEC electrodes and operational conditions.
文摘Due to important consideration of protection against lightning surge on electrical, electronic and telecommunication equipment, it was necessary to carry out a special study to look at the performance of protective devices. The study was testing performance of arresters on low voltage system. The activity was testing of arresters using steady state and impulse voltages. The arresters consisted of gas tube, zener diode, varistor and spark gap arresters, then it was made a cascade circuit between the varistor and spark gap arresters with a decoupling element. The decoupling elements were used air, iron and ferrite. The test yielded data of current and voltage on the tables and oscilloscope waveforms. The arresters had cut voltages early different from each other, namely the gas tube, zener diode, spark gap and varistor arresters were at the voltages of 500 V, 250 V, 1,000 V and 565 V respectively. The iron core decoupling element cascade circuit had the least oscillation among remaining cores.
基金supported by the National Natural Science Foundation of China(21802065 and 12004156)Shenzhen DRC Project[2018]1433+4 种基金Shenzhen Science and Technology Program(KQTD20190929173815000)ShenzhenBasicResearchFund(JCYJ20190809181601639)Guangdong Innovative and Entrepreneurial Research Team Program(2019ZT08C044)The microscopy charaterization was performed at the Pico Center at SUSTech that receives support from the Presidential FundDevelopment and Reform Commission of Shenzhen MunicipalitySUSTech Presidential Postdoctoral Fellowship。
文摘As a promising anode material candidate for sodium-ion batteries,antimony(Sb)has attracted enormous research interest due to its high specific capacity and low sodiation voltage.However,its dramatic volume expansion upon sodiation adversely affects its cycle stability.We have developed an oxidation-coating-reduction strategy for fabricating yolk-shell Sb@C rods from commercially available Sb powder.In particular,the thermal reduction of vaporized Sb_(2)O_(3) generates densely distributed Sb single atoms and clusters on the carbon shell.The sodiation process of the Sb@C sample was recorded through in situ transmission electron microscopy.Irregular expansion of Sb particles was observed,and it was also revealed that the carbon shell could deform with the expanded Sb particles.Beyond the intuitively understood advantage that internal voids can provide space for expansion of internal active materials,the deformability of carbon shells can add further ability to withstand the volume expansion.The two structural merits of the yolk-shell construction enable the Sb@C material to deliver an enhanced cycle performance.Its reversible capacity exceeds 620 mA h g^(−1) at 0.1C,with an initial coulombic efficiency of up to 84.9%,and about 95%of the capacity in the charging voltage profile is delivered below 1.0 V vs.Na+/Na.These performance metrics are very promising for potential practical applications.
基金the funding support from the National Natural Science Foundation of China (51605449, 51675493 and 51705476)Shanxi “1331 Project” Key Subject Construction (1331KSC)
文摘Flexible pressure sensors have attracted great attention due to their potential in the wearable devices market and in particular in human-machine interactive interfaces.Pressure sensors with high sensitivity,wide measurement range,and low-cost are now highly desired for such practical applications.In the present investigation,an ultrasensitive pressure sensor with wide measurement range has been successfully fabricated.Carbon nanotubes(CNTs)(uniformly sprayed on the surface of paper)comprise the sensitivity material,while lithographed interdigital electrodes comprise the substrate.Due to the synergistic effects of CNT’s high specific surface area,paper’s porous structure,interdigital electrodes’efficient contact with CNT,our pressure sensor realizes a wide measurement range from 0 to 140 kPa and exhibits excellent stability through 15,000 cycles of testing.For the paper-based CNT film/interdigitated structure(PCI)pressure sensor,the connection area between the sensitive material and interdigital electrodes dominates in the lowpressure region,while internal change within the sensitive materials plays the leading role in the high-pressure region.Additionally,the PCI pressure sensor not only displays a high sensitivity of 2.72 kPa–1(up to 35 kPa)but also can detect low pressures,such as that exerted by a resting mung bean(about 8 Pa).When attached to the surface of a human body,the pressure sensor can monitor physiological signals,such as wrist movement,pulse beats,or movement of throat muscles.Furthermore,the pressure sensor array can identify the spatial pressure distribution,with promising applications in humanmachine interactive interfaces.
