Heavy metals,notably Pb2+and Cu^(2+),are some of the most persistent contaminants found in groundwater.Frequent monitoring of these metals,which relies on efficient,sensitive,cost-effective,and reliable methods,is a n...Heavy metals,notably Pb2+and Cu^(2+),are some of the most persistent contaminants found in groundwater.Frequent monitoring of these metals,which relies on efficient,sensitive,cost-effective,and reliable methods,is a necessity.We present a nanocomposite-based miniaturized electrode for the concurrent measurement of Pb2+and Cu^(2+)by exploiting the electroanalytical technique of square wave voltammetry.We also propose a facile in situ hydrothermal calcination method to directly grow binder-free mesoporous Ni O on a three-dimensional nickel foam,which is then electrochemically seeded with gold nanoparticles(Au NPs).The meticulous design of a low-barrier Ohmic contact between mesoporous Ni O and Au NPs facilitates target-mediated nanochannel-confined electron transfer within mesoporous Ni O.As a result,the heavy metals Pb2+(0.020 mg.L^(-1)detection limit;2.0–16.0 mg.L^(-1)detection range)and Cu^(2+)(0.013 mg.L^(-1)detection limit;0.4–12.8 mg.L^(-1)detection range)can be detected simultaneously with high precision.Furthermore,other heavy metal ions and common interfering ions found in groundwater showed negligible impacts on the electrode’s performance,and the recovery rate of groundwater samples varied between 96.3%±2.1%and 109.4%±0.6%.The compactness,flexible shape,low power consumption,and ability to remotely operate our electrode pave the way for onsite detection of heavy metals in groundwater,thereby demonstrating the potential to revolutionize the field of environmental monitoring.展开更多
The thermal-electrical characteristic of a GaN light-emitting diode （LED） with the hybrid transparent conductive layers （TCLs） of graphene （Gr） and NiOx is investigated by a finite element method. It is indicate...The thermal-electrical characteristic of a GaN light-emitting diode （LED） with the hybrid transparent conductive layers （TCLs） of graphene （Gr） and NiOx is investigated by a finite element method. It is indicated that the LED with the compound TCL of 3-layer Gr and 1 nm NiOx has the best thermal-electrical performance from the view point of the maximum temperature and the current density deviation of multiple quantum wells, and the maximum temperature occurs near the n-electrode rather than p-electrode. Furthermore, to depress the current crowding on the LED, the electrode pattern parameters including p- and n-electrode length, p-electrode buried depth and the distance of n-electrode to active area are optimized. It is found that either increasing p- or n-electrode length and buried depth or decreasing the distance of n-electrode from the active area will decrease the temperature of the LED, while the increase of the n-electrode length has more prominent effect. Typically, when the n-electrode length increases to 0.8 times of the chip size, the temperature of the GaN LED with the inm NiOx/3-1ayer-Gr hybrid TCLs could drop about 7K and the current density uniformity could increase by 23.8%, compared to 0.4 times of the chip size. This new finding will be beneficial for improvement of the thermal- electrical performance of LEDs with various conductive TCLs such as NiOx/Gr or ITO/Gr as current spreading layers.展开更多
采用原位水热生长法在泡沫镍基底上制备了β-Ni(OH)2纳米盘并通过煅烧获得NiO,均可以直接作为工作电极。利用XRD和SEM对样品进行了表征,并进行了电化学性能测试,结果表明我们所制备的Ni(OH)2电极在2 M KOH溶液中2.5 A/g的放电电流密度下...采用原位水热生长法在泡沫镍基底上制备了β-Ni(OH)2纳米盘并通过煅烧获得NiO,均可以直接作为工作电极。利用XRD和SEM对样品进行了表征,并进行了电化学性能测试,结果表明我们所制备的Ni(OH)2电极在2 M KOH溶液中2.5 A/g的放电电流密度下,比容量达1495 F/g,通过煅烧得到的NiO,同样可以作为电极材料。展开更多
With the rapid emergence of wearable devices, flexible lithium-ion batteries(LIBs) are much more needed than ever. Free-standing graphene-based composite paper electrodes with various active materials have appealed wi...With the rapid emergence of wearable devices, flexible lithium-ion batteries(LIBs) are much more needed than ever. Free-standing graphene-based composite paper electrodes with various active materials have appealed wide applications in flexible LIBs. However, due to the prone-to-restacking feature of graphene layers, a long cycle life at high current densities is rather difficult to be achieved. Herein, a unique threedimensional(3D) hierarchically porous NiO micro-flowers/graphene paper(fNiO/GP) electrode is successfully fabricated. The resulting fNiO/GP electrode shows superior long-term cycling stability at high rates(e.g., storage capacity of 359 mAh/g after 600 cycles at a high current density of 1 A/g). The facile 3D porous structure combines both the advantages of the graphene that is highly conductive and flexible to ensure rapid electrons/ions transfer and buffer the volume expansion of NiO during charge/discharge,and of the micro-sized NiO flowers that induces hierarchical between-layer pores ranging from nanomicro meters to promote the penetration of the electrolyte and prevent the re-stacking of graphene layers. Such structural design will inspire future manufacture of a wide range of active materials/graphene composite electrodes for high performance flexible LIBs.展开更多
Developing high power and energy supercapacitors(SCs)is a long-pursued goal for the application in transportation and energy storage station.Herein,a rationally-designed Co-doped nickel oxide nanosheets@carbon-welded ...Developing high power and energy supercapacitors(SCs)is a long-pursued goal for the application in transportation and energy storage station.Herein,a rationally-designed Co-doped nickel oxide nanosheets@carbon-welded carbon nanotube foam(Co-doped NiO@WCNTF)as freestanding electrode is successfully prepared for high power and energy SCs.The WCNTF framework with high specific surface area provides three dimensional highly conductive network for fast charge transport and ensures high loading of active materials(9.2 mg/cm2).Moreover,porous Co-doped NiO nanosheets uniformly anchored on the WCNTF framework enable rapid charge kinetics due to the high intrinsic conductivity of Co-doped Ni O nanosheets and their good contact with conductive WCNTF substrate.As a result,the unique integrated electrode with 3D architecture exhibits an ultrahigh specific capacitance of 11.45 F/cm2 at 5 mA/cm2,outstanding rate capability(11.45 F/cm2 at 5 mA/cm2 and a capacitance retention of 86.2%at 30 mA/cm2)and good cycling stability,suggesting great potential for high performance supercapacitor.展开更多
基金supported by the National Key Research and Development Project of China(2019YFC1804802)。
文摘Heavy metals,notably Pb2+and Cu^(2+),are some of the most persistent contaminants found in groundwater.Frequent monitoring of these metals,which relies on efficient,sensitive,cost-effective,and reliable methods,is a necessity.We present a nanocomposite-based miniaturized electrode for the concurrent measurement of Pb2+and Cu^(2+)by exploiting the electroanalytical technique of square wave voltammetry.We also propose a facile in situ hydrothermal calcination method to directly grow binder-free mesoporous Ni O on a three-dimensional nickel foam,which is then electrochemically seeded with gold nanoparticles(Au NPs).The meticulous design of a low-barrier Ohmic contact between mesoporous Ni O and Au NPs facilitates target-mediated nanochannel-confined electron transfer within mesoporous Ni O.As a result,the heavy metals Pb2+(0.020 mg.L^(-1)detection limit;2.0–16.0 mg.L^(-1)detection range)and Cu^(2+)(0.013 mg.L^(-1)detection limit;0.4–12.8 mg.L^(-1)detection range)can be detected simultaneously with high precision.Furthermore,other heavy metal ions and common interfering ions found in groundwater showed negligible impacts on the electrode’s performance,and the recovery rate of groundwater samples varied between 96.3%±2.1%and 109.4%±0.6%.The compactness,flexible shape,low power consumption,and ability to remotely operate our electrode pave the way for onsite detection of heavy metals in groundwater,thereby demonstrating the potential to revolutionize the field of environmental monitoring.
基金Supported by the Foundation of the State Key Laboratory of Mechanical Transmission of Chongqing University under Grant Nos SKLMT-KFKT-201419 and SKLM-ZZKT-2015Z16the National High-Technology Research and Development Program of China under Grant No 2015AA034801+4 种基金the National Natural Science Foundation of China under Grant Nos 11374359,11304405,11544010 and 11547305the Chongqing Education Commission Scientific Project under Grant No KJ132209the Natural Science Foundation of Chongqing under Grant Nos cstc2013jcyjA50031,cstc2015jcyjA50035 and cstc2015jcyjA1660the Fundamental Research Funds for the Central Universities under Grant Nos CDJZR14135502,CDJZR14300050,106112016CDJZR288805 and 106112015CDJXY300002the Sharing Fund of Large-scale Equipment of Chongqing University under Grant Nos 201512150017,201512150029 and 201512150030
文摘The thermal-electrical characteristic of a GaN light-emitting diode （LED） with the hybrid transparent conductive layers （TCLs） of graphene （Gr） and NiOx is investigated by a finite element method. It is indicated that the LED with the compound TCL of 3-layer Gr and 1 nm NiOx has the best thermal-electrical performance from the view point of the maximum temperature and the current density deviation of multiple quantum wells, and the maximum temperature occurs near the n-electrode rather than p-electrode. Furthermore, to depress the current crowding on the LED, the electrode pattern parameters including p- and n-electrode length, p-electrode buried depth and the distance of n-electrode to active area are optimized. It is found that either increasing p- or n-electrode length and buried depth or decreasing the distance of n-electrode from the active area will decrease the temperature of the LED, while the increase of the n-electrode length has more prominent effect. Typically, when the n-electrode length increases to 0.8 times of the chip size, the temperature of the GaN LED with the inm NiOx/3-1ayer-Gr hybrid TCLs could drop about 7K and the current density uniformity could increase by 23.8%, compared to 0.4 times of the chip size. This new finding will be beneficial for improvement of the thermal- electrical performance of LEDs with various conductive TCLs such as NiOx/Gr or ITO/Gr as current spreading layers.
文摘采用原位水热生长法在泡沫镍基底上制备了β-Ni(OH)2纳米盘并通过煅烧获得NiO,均可以直接作为工作电极。利用XRD和SEM对样品进行了表征,并进行了电化学性能测试,结果表明我们所制备的Ni(OH)2电极在2 M KOH溶液中2.5 A/g的放电电流密度下,比容量达1495 F/g,通过煅烧得到的NiO,同样可以作为电极材料。
基金financially supported by the National Key R&D Program of China (No.2017YFE0111500)the National Natural Science Foundation of China (No.51673123 and 51222305)Sichuan Province Science and Technology Project (No.2016JQ0049)。
文摘With the rapid emergence of wearable devices, flexible lithium-ion batteries(LIBs) are much more needed than ever. Free-standing graphene-based composite paper electrodes with various active materials have appealed wide applications in flexible LIBs. However, due to the prone-to-restacking feature of graphene layers, a long cycle life at high current densities is rather difficult to be achieved. Herein, a unique threedimensional(3D) hierarchically porous NiO micro-flowers/graphene paper(fNiO/GP) electrode is successfully fabricated. The resulting fNiO/GP electrode shows superior long-term cycling stability at high rates(e.g., storage capacity of 359 mAh/g after 600 cycles at a high current density of 1 A/g). The facile 3D porous structure combines both the advantages of the graphene that is highly conductive and flexible to ensure rapid electrons/ions transfer and buffer the volume expansion of NiO during charge/discharge,and of the micro-sized NiO flowers that induces hierarchical between-layer pores ranging from nanomicro meters to promote the penetration of the electrolyte and prevent the re-stacking of graphene layers. Such structural design will inspire future manufacture of a wide range of active materials/graphene composite electrodes for high performance flexible LIBs.
基金the National Natural Science Foundation of China(U1710122,51862035 and 21773293)the Science and Technology Project of Jiangxi Province(20181ACH80008,20181ACE50012,20192BCD40017 and 20192ACB80002)+1 种基金Jiangxi Double Thousand Talent Program(S2018LQCQ0016)Suzhou Science and Technology Plan Projects(SYG201831)。
文摘Developing high power and energy supercapacitors(SCs)is a long-pursued goal for the application in transportation and energy storage station.Herein,a rationally-designed Co-doped nickel oxide nanosheets@carbon-welded carbon nanotube foam(Co-doped NiO@WCNTF)as freestanding electrode is successfully prepared for high power and energy SCs.The WCNTF framework with high specific surface area provides three dimensional highly conductive network for fast charge transport and ensures high loading of active materials(9.2 mg/cm2).Moreover,porous Co-doped NiO nanosheets uniformly anchored on the WCNTF framework enable rapid charge kinetics due to the high intrinsic conductivity of Co-doped Ni O nanosheets and their good contact with conductive WCNTF substrate.As a result,the unique integrated electrode with 3D architecture exhibits an ultrahigh specific capacitance of 11.45 F/cm2 at 5 mA/cm2,outstanding rate capability(11.45 F/cm2 at 5 mA/cm2 and a capacitance retention of 86.2%at 30 mA/cm2)and good cycling stability,suggesting great potential for high performance supercapacitor.
