Converting carbon dioxide(CO2)into value-added chemicals by CO2 reduction has been considered as a potential way to solve the current energy crisis and environmental problem.Among the methods of CO2 reduction,the elec...Converting carbon dioxide(CO2)into value-added chemicals by CO2 reduction has been considered as a potential way to solve the current energy crisis and environmental problem.Among the methods of CO2 reduction,the electrochemical method has been widely used due to its mild reaction condition and high reaction efficiency.In the electrochemical reduction system,the CO2 electrocatalyst is the most important part.Although many CO2 electrocatalysts have been developed,efficient catalysts with high activity,selectivity and stability are still lacking.Copper sulfide compound,as a low-toxicity and emerging material,has broad prospects in the field of CO2 reduction due to its unique structural and electrochemical properties.Much progress has been achieved with copper sulfide nanocrystalline and the field is rapidly developing.This paper summarizes the preparation,recent progress in development,and factors affecting the electrocatalytic CO2 reduction performance with copper sulfide compound as a catalyst.Prospects for future development are also outlined,with the aim of using copper sulfide compound as a highly active and stable electrocatalyst for CO2 reduction.展开更多
Now,Pt-based materials are still the best catalysts for hydrogen evolution reaction(HER).Nevertheless,the scarcity of Pt makes it impossible for the large-scale applications in industry.Although cobalt is taken as an ...Now,Pt-based materials are still the best catalysts for hydrogen evolution reaction(HER).Nevertheless,the scarcity of Pt makes it impossible for the large-scale applications in industry.Although cobalt is taken as an excellent HER catalyst due to its suitable H*binding,its alkali HER catalytic property need to be improved because of the sluggish water dissociation kinetics.In this work,nitrogen with small atomic radius and metallophilicity is employed to adjust local charges of atomically dispersed Mo^(δ+)sites on Co nanosheets to trigger water dissociation.Theoretical calculations suggest that the energy barrier of water dissociation can be effectively reduced by introducing nitrogen coordinated Mo^(δ+)sites.To realize this speculation,atomically dispersed Mo^(δ+)sites with nitrogen coordination of Mo(N)/Co were prepared via reconstruction of CoMoO_(4).High angle annular dark-field scanning transmission electron microscopy(HAADF-STEM)and X-ray absorption spectroscopy(XAS)demonstrate the coordination of N atoms with atomically dispersed Mo atoms,leading to the local charges of atomically dispersed Mo^(δ+)sites in Mo(N)/Co.The measurement from ambient pressure X-ray photoelectron spectroscopy(AP-XPS)reveals that the Mo^(δ+)sites promote the adsorption and activation of water molecule.Therefore,the Mo(N)/Co exhibits an excellent activity,which need only an overpotential of 39 mV to reach the current density of 10 mA cm^(-2).The proposed strategy provides an advance pathway to design and boost alkaline HER activity at the atomic-level.展开更多
Electrocatalytic CO_(2)reduction reaction(CO_(2)RR)holds significant promise for sustainable energy conversion,with cobalt phthalocyanine(CoPc)emerging as a notable catalyst due to its high CO selectivity.However,CoPc...Electrocatalytic CO_(2)reduction reaction(CO_(2)RR)holds significant promise for sustainable energy conversion,with cobalt phthalocyanine(CoPc)emerging as a notable catalyst due to its high CO selectivity.However,CoPc's efficacy is hindered by its limited ability to provide sufficient proton for the protonation process,particularly at industrial current densities.Herein,we introduce defect-engineered carbon nanotubes(d-CNT)to augment proton feeding for CO_(2)RR over CoPc,achieved by expediting water dissociation.Our kinetic measurements and in-situ attenuated total reflection surface-enhanced infrared absorption spectroscopy reveal d-CNT significantly enhances proton feeding,thereby facilitating CO_(2)activation to*COOH in CoPc.Density functional theory calculations corroborate these findings,illustrating that d-CNT decreases the barrier to water dissociation.Consequently,the CoPc/d-CNT mixture demonstrates robust performance,achieving 500 mA cm^(-2)for CO_(2)RR with CO selectivity exceeding 96%.Notably,CoPc/d-CNT remains stability for a duration of 20 h under a substantial current density of 150 mA cm^(-2).The study broadens the scope of practical applications for molecular catalysts in CO_(2)RR,marking a significant step towards sustainable energy conversion.展开更多
Polycrystalline Si(poly-Si)-based passivating contacts are promising candidates for high-efficiency crystalline Si solar cells.We show that nanosecond-scale pulsed laser melting(PLM)is an industrially viable technique...Polycrystalline Si(poly-Si)-based passivating contacts are promising candidates for high-efficiency crystalline Si solar cells.We show that nanosecond-scale pulsed laser melting(PLM)is an industrially viable technique to fabricate such contacts with precisely controlled dopant concentration profiles that exceed the solid solubility limit.We demonstrate that conventionally doped,hole-selective poly-Si/SiO_(x)contacts that provide poor surface passivation of c-Si can be replaced with Ga-or B-doped contacts based on non-equilibrium doping.We overcome the solid solubility limit for both dopants in poly-Si by rapid cooling and recrystallization over a timescale of∼25 ns.We show an active Ga dopant concentration of∼3×10^(20)cm^(−3)in poly-Si which is six times higher than its solubility limit in c-Si,and a B dopant concentration as high as∼10^(21) cm^(−3).We measure an implied open-circuit voltage of 735 mV for Ga-doped poly-Si/SiO_(x)contacts on Czochralski Si with a low contact resistivity of 35.5±2.4 mΩcm^(2).Scanning spreading resistance microscopy and Kelvin probe force microscopy show large diffusion and drift current in the p-n junction that contributes to the low contact resistivity.Our results suggest that PLM can be extended for hyperdoping of other semiconductors with low solubility atoms to enable high-efficiency devices.展开更多
Convex relaxations and approximations of the optimal power flow(OPF)problem have gained significant research and industrial interest for planning and operations in electric power networks.One approach for reducing the...Convex relaxations and approximations of the optimal power flow(OPF)problem have gained significant research and industrial interest for planning and operations in electric power networks.One approach for reducing their solve times is presolving which eliminates constraints from the problem definition,thereby reducing the burden of the underlying optimization algorithm.To this end,we propose a presolving framework for convexified optimal power flow(C-OPF)problems,which uses a novel deep learning-based architecture called𝙼MoGE(Mixture of Gradient Experts).In this framework,problem size is reduced by learning the mapping between C-OPF parameters and optimal dual variables(the latter being representable as gradients),which is then used to screen constraints that are non-binding at optimum.The validity of using this presolve framework across arbitrary families of C-OPF problems is theoretically demonstrated.We characterize generalization in𝙼𝚘𝙶𝙴and develop a post-solve recovery procedure to mitigate possible constraint classification errors.Using two different C-OPF models,we show via simulations that our framework reduces solve times by upto 34%across multiple PGLIB and MATPOWER test cases,while providing an identical solution as the full problem.展开更多
Pain management has become a prominent global health concern,affecting not only over the aspects of daily existence but also upon the holistic physical well-being.Conventional pain management methods have non-negligib...Pain management has become a prominent global health concern,affecting not only over the aspects of daily existence but also upon the holistic physical well-being.Conventional pain management methods have non-negligible limitations,such as the discomfort caused by needle injections and the low permeability of transdermal drug patches due to the skin barriers.Microneedle-based drug delivery is an emerging technique that utilizes microscopic needles to directly administer medication into the epidermis or dermis,offering the advantages of enhanced efficiency,rapid action,and minimally invasive delivery.Regarding to the analgesic therapy,microneedles are at the forefront,accelerating pain relief by localized delivery of analgesic substances directly to the site of discomfort.The targeted administration effectively reduces the broader dispersion of pharmacological agents within the circulatory system,thereby minimizing the occurrence of systemic adverse effects.This review focuses on the utilization of microneedle technology for both immediate and extended pain relief,its performance in clinical practice,and the prospects and challenges of microneedles in pain management therapy.展开更多
To monitor the freshness of chicken,a pH-sensitive film based on sodium alginate,gelatin,and plum peel extract(SGPE)was created.Thickness,color,water contact angle,mechanical characteristics,water content,water vapor ...To monitor the freshness of chicken,a pH-sensitive film based on sodium alginate,gelatin,and plum peel extract(SGPE)was created.Thickness,color,water contact angle,mechanical characteristics,water content,water vapor transmission,light transmission,and pH sensitivity were used to evaluate the performance of the film sample.SEM and FTIR graphs demonstrated that adding plum peel extract made the SGPE film’s internal structure more denser and increased its mechanical property,while decreasing the water contact angle,water content,and WVP value.The color of the SGPE15 film clearly changed from red to yellow-green in various buffer solutions(pH=1-14),demonstrating more pH sensitivity than the SG,SGPE5,and SGPE10 films.On day 6,when checking the freshness of chicken kept at 4℃,the SGPE15 film’s color changed from orange-pink to yellow-green with TVB-N level beyond the allowable limit(15 mg/100 g).The result revealed that the SGPE film might be applied to monitor the freshness of chicken breast flesh.展开更多
In statistical planning of experiments, super-simple designs are the ones providing samples with maximum intersection as small as possible. Super- simple group divisible designs are useful in constructing other types ...In statistical planning of experiments, super-simple designs are the ones providing samples with maximum intersection as small as possible. Super- simple group divisible designs are useful in constructing other types of super- simple designs which can be applied to codes and designs. In this article, the existence of a super-simple （5, 4）-GDD of group type gU is investigated and it is shown that such a design exists if and only if u ≥ 5, g（u - 2） ≥ 12, and u（u - 1）g^2≡ 0 （mod 5） with some possible exceptions.展开更多
基金the National Postdoctoral Program for Innovative Talents of China,Postdoctoral Science Foundation of China(Grant No.2018M640759)Natural Science Foundation of China(Grant No.21872174 and U1932148)+4 种基金Project of Innovation-Driven Plan in Central South University(Grant No.20180018050001)State Key Laboratory of Powder Metallurgy,International Science and Technology Cooperation Program(Grant No.2017YFE0127800)Hunan Provincial Science and Technology Program(2017XK2026)Shenzhen Science and Technology Innovation Project(Grant No.JCYJ20180307151313532)Thousand Youth Talents Plan of China and Hundred Youth Talents Program of Hunan.
文摘Converting carbon dioxide(CO2)into value-added chemicals by CO2 reduction has been considered as a potential way to solve the current energy crisis and environmental problem.Among the methods of CO2 reduction,the electrochemical method has been widely used due to its mild reaction condition and high reaction efficiency.In the electrochemical reduction system,the CO2 electrocatalyst is the most important part.Although many CO2 electrocatalysts have been developed,efficient catalysts with high activity,selectivity and stability are still lacking.Copper sulfide compound,as a low-toxicity and emerging material,has broad prospects in the field of CO2 reduction due to its unique structural and electrochemical properties.Much progress has been achieved with copper sulfide nanocrystalline and the field is rapidly developing.This paper summarizes the preparation,recent progress in development,and factors affecting the electrocatalytic CO2 reduction performance with copper sulfide compound as a catalyst.Prospects for future development are also outlined,with the aim of using copper sulfide compound as a highly active and stable electrocatalyst for CO2 reduction.
基金the International Science and Technology Cooperation Program(2017YFE0127800 and 2018YFE0203400)the Natural Science Foundation of China(21872174,21762036 and U1932148)+7 种基金the Hunan Provincial Science and Technology Program(2017XK2026)the Shenzhen Science and Technology Innovation Project(JCYJ20180307151313532)Innovation and Entrepreneurship Training Program for College Students(S202110670023)the Natural Science Foundation of Science and Technology Department of Guizhou Province([2019]1297)the Special Project of Science and Technology Department of Guizhou Province([2020]QNSYXM03)the Natural Science Foundation of Education Department of Guizhou Province([2019]213,[2015]66)Teaching Quality Improvement Project of Qiannan Normal University for Nationalities([2017]50)the Beam Lines of BL01C1,BL24A1 in the NSRRC(MOST 109-2113-M-213-002)and beamline BL10B in National Synchrotron Radiation Laboratory。
文摘Now,Pt-based materials are still the best catalysts for hydrogen evolution reaction(HER).Nevertheless,the scarcity of Pt makes it impossible for the large-scale applications in industry.Although cobalt is taken as an excellent HER catalyst due to its suitable H*binding,its alkali HER catalytic property need to be improved because of the sluggish water dissociation kinetics.In this work,nitrogen with small atomic radius and metallophilicity is employed to adjust local charges of atomically dispersed Mo^(δ+)sites on Co nanosheets to trigger water dissociation.Theoretical calculations suggest that the energy barrier of water dissociation can be effectively reduced by introducing nitrogen coordinated Mo^(δ+)sites.To realize this speculation,atomically dispersed Mo^(δ+)sites with nitrogen coordination of Mo(N)/Co were prepared via reconstruction of CoMoO_(4).High angle annular dark-field scanning transmission electron microscopy(HAADF-STEM)and X-ray absorption spectroscopy(XAS)demonstrate the coordination of N atoms with atomically dispersed Mo atoms,leading to the local charges of atomically dispersed Mo^(δ+)sites in Mo(N)/Co.The measurement from ambient pressure X-ray photoelectron spectroscopy(AP-XPS)reveals that the Mo^(δ+)sites promote the adsorption and activation of water molecule.Therefore,the Mo(N)/Co exhibits an excellent activity,which need only an overpotential of 39 mV to reach the current density of 10 mA cm^(-2).The proposed strategy provides an advance pathway to design and boost alkaline HER activity at the atomic-level.
文摘Electrocatalytic CO_(2)reduction reaction(CO_(2)RR)holds significant promise for sustainable energy conversion,with cobalt phthalocyanine(CoPc)emerging as a notable catalyst due to its high CO selectivity.However,CoPc's efficacy is hindered by its limited ability to provide sufficient proton for the protonation process,particularly at industrial current densities.Herein,we introduce defect-engineered carbon nanotubes(d-CNT)to augment proton feeding for CO_(2)RR over CoPc,achieved by expediting water dissociation.Our kinetic measurements and in-situ attenuated total reflection surface-enhanced infrared absorption spectroscopy reveal d-CNT significantly enhances proton feeding,thereby facilitating CO_(2)activation to*COOH in CoPc.Density functional theory calculations corroborate these findings,illustrating that d-CNT decreases the barrier to water dissociation.Consequently,the CoPc/d-CNT mixture demonstrates robust performance,achieving 500 mA cm^(-2)for CO_(2)RR with CO selectivity exceeding 96%.Notably,CoPc/d-CNT remains stability for a duration of 20 h under a substantial current density of 150 mA cm^(-2).The study broadens the scope of practical applications for molecular catalysts in CO_(2)RR,marking a significant step towards sustainable energy conversion.
基金the National Renewable Energy Laboratory,operated by Alliance for Sustainable Energy,LLC,for the U.S.Department of Energy(DOE)under Contract No.DE-AC36-08GO28308.
文摘Polycrystalline Si(poly-Si)-based passivating contacts are promising candidates for high-efficiency crystalline Si solar cells.We show that nanosecond-scale pulsed laser melting(PLM)is an industrially viable technique to fabricate such contacts with precisely controlled dopant concentration profiles that exceed the solid solubility limit.We demonstrate that conventionally doped,hole-selective poly-Si/SiO_(x)contacts that provide poor surface passivation of c-Si can be replaced with Ga-or B-doped contacts based on non-equilibrium doping.We overcome the solid solubility limit for both dopants in poly-Si by rapid cooling and recrystallization over a timescale of∼25 ns.We show an active Ga dopant concentration of∼3×10^(20)cm^(−3)in poly-Si which is six times higher than its solubility limit in c-Si,and a B dopant concentration as high as∼10^(21) cm^(−3).We measure an implied open-circuit voltage of 735 mV for Ga-doped poly-Si/SiO_(x)contacts on Czochralski Si with a low contact resistivity of 35.5±2.4 mΩcm^(2).Scanning spreading resistance microscopy and Kelvin probe force microscopy show large diffusion and drift current in the p-n junction that contributes to the low contact resistivity.Our results suggest that PLM can be extended for hyperdoping of other semiconductors with low solubility atoms to enable high-efficiency devices.
基金supported by the 2023 CITRIS Interdisciplinary Innovation Program(I2P),USA and the UCSC Dissertation-Year Fellowship,USA.
文摘Convex relaxations and approximations of the optimal power flow(OPF)problem have gained significant research and industrial interest for planning and operations in electric power networks.One approach for reducing their solve times is presolving which eliminates constraints from the problem definition,thereby reducing the burden of the underlying optimization algorithm.To this end,we propose a presolving framework for convexified optimal power flow(C-OPF)problems,which uses a novel deep learning-based architecture called𝙼MoGE(Mixture of Gradient Experts).In this framework,problem size is reduced by learning the mapping between C-OPF parameters and optimal dual variables(the latter being representable as gradients),which is then used to screen constraints that are non-binding at optimum.The validity of using this presolve framework across arbitrary families of C-OPF problems is theoretically demonstrated.We characterize generalization in𝙼𝚘𝙶𝙴and develop a post-solve recovery procedure to mitigate possible constraint classification errors.Using two different C-OPF models,we show via simulations that our framework reduces solve times by upto 34%across multiple PGLIB and MATPOWER test cases,while providing an identical solution as the full problem.
基金This work was financially supported by the National Natural Science Foundation of China(Nos.52161145410,52373126,and 52303173)Beijing University of Chemical Technology-China Japan Friendship Hospital Biomedical Translational Engineering Research Center Key Projects(No.XK2023-20)+2 种基金Grant from State Key Laboratory of Organic-Inorganic Composites(No.oic 202401005)the Fundamental Research funds for the Central Universities(No.ZY2453)the long-term subsidy mechanism from the Ministry of Finance and the Ministry of Education of PRC.
文摘Pain management has become a prominent global health concern,affecting not only over the aspects of daily existence but also upon the holistic physical well-being.Conventional pain management methods have non-negligible limitations,such as the discomfort caused by needle injections and the low permeability of transdermal drug patches due to the skin barriers.Microneedle-based drug delivery is an emerging technique that utilizes microscopic needles to directly administer medication into the epidermis or dermis,offering the advantages of enhanced efficiency,rapid action,and minimally invasive delivery.Regarding to the analgesic therapy,microneedles are at the forefront,accelerating pain relief by localized delivery of analgesic substances directly to the site of discomfort.The targeted administration effectively reduces the broader dispersion of pharmacological agents within the circulatory system,thereby minimizing the occurrence of systemic adverse effects.This review focuses on the utilization of microneedle technology for both immediate and extended pain relief,its performance in clinical practice,and the prospects and challenges of microneedles in pain management therapy.
基金support from the National Natural Science Foundation of China(No.22268024,32060569,and 21576126).
文摘To monitor the freshness of chicken,a pH-sensitive film based on sodium alginate,gelatin,and plum peel extract(SGPE)was created.Thickness,color,water contact angle,mechanical characteristics,water content,water vapor transmission,light transmission,and pH sensitivity were used to evaluate the performance of the film sample.SEM and FTIR graphs demonstrated that adding plum peel extract made the SGPE film’s internal structure more denser and increased its mechanical property,while decreasing the water contact angle,water content,and WVP value.The color of the SGPE15 film clearly changed from red to yellow-green in various buffer solutions(pH=1-14),demonstrating more pH sensitivity than the SG,SGPE5,and SGPE10 films.On day 6,when checking the freshness of chicken kept at 4℃,the SGPE15 film’s color changed from orange-pink to yellow-green with TVB-N level beyond the allowable limit(15 mg/100 g).The result revealed that the SGPE film might be applied to monitor the freshness of chicken breast flesh.
基金Acknowledgements This work was supported by the National Natural Science Foundation of China （Grant Nos. 11371121, 11371308, 11201114, 11301457）.
文摘In statistical planning of experiments, super-simple designs are the ones providing samples with maximum intersection as small as possible. Super- simple group divisible designs are useful in constructing other types of super- simple designs which can be applied to codes and designs. In this article, the existence of a super-simple （5, 4）-GDD of group type gU is investigated and it is shown that such a design exists if and only if u ≥ 5, g（u - 2） ≥ 12, and u（u - 1）g^2≡ 0 （mod 5） with some possible exceptions.
