Cuprous oxide(Cu_(2)O) is one of the most promising catalysts for electrochemical conversion of CO_(2) into value-added C_(2) products.The efficiency of CO_(2)-to-C_(2) conversion is highly dependent on the Cu_(2)O cr...Cuprous oxide(Cu_(2)O) is one of the most promising catalysts for electrochemical conversion of CO_(2) into value-added C_(2) products.The efficiency of CO_(2)-to-C_(2) conversion is highly dependent on the Cu_(2)O crystal plane orientation and the corresponding adsorbed ^(*)CO species.Herein,we constructed high-index crystal planes(311) in Cu_(2)O(CO-Cu_(2)O) via a facile self-selective CO-induced strategy under a CO atmosphere,which was verified by high-resolution transmission electron microscopy(HR-TEM) and atomic force microscopy(AFM) results.By exploiting the high surface energy of the high index crystal planes,^(*)CO species are stabilized in CO-Cu_(2)O during CO_(2)RR,resulting in exceptional catalytic performance for CO_(2)-to-C_(2)products.In situ infrared spectroscopy revealed that both atop-type(^(*)CO_(atop)) and hollow-type(^(*)CO_(hollow)) adsorption of ^(*)CO species occurred on the CO-Cu_(2)O.The asymmetric C-C coupling energy barrier between ^(*)CO_(atop) and ^(*)CO_(hollow) in(311) crystal plane decreases by 47.8 % compared to the symmetric coupling of ^(*)CO_(atop) in conventional(100) crystal planes.Consequently,the Faradaic efficiency of C_(2) products generated with CO-Cu_(2)O was increased by as high as 100 % compared to that with pristine Cu_(2)O.展开更多
Severe ground-level ozone(O_(3))pollution over major Chinese cities has become one of the most challenging problems,which have deleterious effects on human health and the sustainability of society.This study explored ...Severe ground-level ozone(O_(3))pollution over major Chinese cities has become one of the most challenging problems,which have deleterious effects on human health and the sustainability of society.This study explored the spatiotemporal distribution characteristics of ground-level O_(3) and its precursors based on conventional pollutant and meteorological monitoring data in Zhejiang Province from 2016 to 2021.Then,a high-performance convolutional neural network(CNN)model was established by expanding the moment and the concentration variations to general factors.Finally,the response mechanism of O_(3) to the variation with crucial influencing factors is explored by controlling variables and interpolating target variables.The results indicated that the annual average MDA8-90th concentrations in Zhejiang Province are higher in the northern and lower in the southern.When the wind direction(WD)ranges from east to southwest and the wind speed(WS)ranges between 2 and 3 m/sec,higher O_(3) concentration prone to occur.At different temperatures(T),the O_(3) concentration showed a trend of first increasing and subsequently decreasing with increasing NO_(2) concentration,peaks at the NO_(2) concentration around 0.02mg/m^(3).The sensitivity of NO_(2) to O_(3) formation is not easily affected by temperature,barometric pressure and dew point temperature.Additionally,there is a minimum IRNO_(2) at each temperature when the NO_(2) concentration is 0.03 mg/m^(3),and this minimum IRNO_(2) decreases with increasing temperature.The study explores the response mechanism of O_(3) with the change of driving variables,which can provide a scientific foundation and methodological support for the targeted management of O_(3) pollution.展开更多
The electrochemical carbon dioxide reduction reaction(CO_(2)RR)to high value-added fuels or chemicals driven by the renewable energy is promising to alleviate global warming.However,the selective CO_(2)reduction to C_...The electrochemical carbon dioxide reduction reaction(CO_(2)RR)to high value-added fuels or chemicals driven by the renewable energy is promising to alleviate global warming.However,the selective CO_(2)reduction to C_(2)products remains challenge.Cu-based catalyst with the specific Cu^(0)and Cu^(+)sites is important to generate C_(2)products.This work used nitrogen(N)to tune amounts of Cu^(0)and Cu^(+)sites in Cu_(2)O catalysts and improve C_(2)-product conversion.The controllable Cu^(0)/Cu^(+)ratio of Cu_(2)O catalyst from 0.16 to 15.19 was achieved by adjusting the N doping amount using NH3/Ar plasma treatment.The major theme of this work was clarifying a volcano curve of the ethylene Faraday efficiency as a function of the Cu^(0)/Cu^(+)ratio.The optimal Cu^(0)/Cu^(+)ratio was determined as 0.43 for selective electroreduction CO_(2)to ethylene.X-ray spectroscopy and density functional theory(DFT)calculations were employed to elucidate that the strong interaction between N and Cu increased the binding energy of N–Cu bond and stabilize Cu^(+),resulting in a 92.3%reduction in the potential energy change for^(∗)CO-^(∗)CO dimerization.This study is inspiring in designing high performance electrocatalysts for CO_(2)conversion.展开更多
A nitrogen-polarity(N-polarity)GaN-based high electron mobility transistor(HEMT)shows great potential for high-fre-quency solid-state power amplifier applications because its two-dimensional electron gas(2DEG)density ...A nitrogen-polarity(N-polarity)GaN-based high electron mobility transistor(HEMT)shows great potential for high-fre-quency solid-state power amplifier applications because its two-dimensional electron gas(2DEG)density and mobility are mini-mally affected by device scaling.However,the Schottky barrier height(SBH)of N-polarity GaN is low.This leads to a large gate leakage in N-polarity GaN-based HEMTs.In this work,we investigate the effect of annealing on the electrical characteristics of N-polarity GaN-based Schottky barrier diodes(SBDs)with Ni/Au electrodes.Our results show that the annealing time and tem-perature have a large influence on the electrical properties of N-polarity GaN SBDs.Compared to the N-polarity SBD without annealing,the SBH and rectification ratio at±5 V of the SBD are increased from 0.51 eV and 30 to 0.77 eV and 7700,respec-tively,and the ideal factor of the SBD is decreased from 1.66 to 1.54 after an optimized annealing process.Our analysis results suggest that the improvement of the electrical properties of SBDs after annealing is mainly due to the reduction of the inter-face state density between Schottky contact metals and N-polarity GaN and the increase of barrier height for the electron emis-sion from the trap state at low reverse bias.展开更多
Volatile organic compound(VOC) emission control and source apportionment in small-scale industrial areas have become key topics of air pollution control in China. This study proposed a novel characteristic factor and ...Volatile organic compound(VOC) emission control and source apportionment in small-scale industrial areas have become key topics of air pollution control in China. This study proposed a novel characteristic factor and pattern recognition(CF-PR) model for VOC source apportionment based on the similarity of characteristic factors between sources and receptors.A simulation was carried out in a typical industrial area with the CF-PR model involving simulated receptor samples. Refined and accurate source profiles were constructed through in situ sampling and analysis, covering rubber, chemicals, coating, electronics, plastics, printing, incubation and medical treatment industries. Characteristic factors of n-undecane,styrene, o-xylene and propane were identified. The source apportionment simulation results indicated that the predicted contribution rate was basically consistent with the real contribution rate. Compared to traditional receptor models, this method achieves notable advantages in terms of refinement and timeliness at similar accuracy, which is more suitable for VOC source identification and apportionment in small-scale industrial areas.展开更多
Volatile organic compounds(VOCs)are the dominant pollutants in industrial parks.However,they are not generally considered as part of the air quality index(AQI)system,which leads to a biased assessment of pollution in ...Volatile organic compounds(VOCs)are the dominant pollutants in industrial parks.However,they are not generally considered as part of the air quality index(AQI)system,which leads to a biased assessment of pollution in industrial parks.In this study,a supplementary assessment system of AQI-V was established by analyzing VOCs characteristics with vehicle-mounted PTR-TOFMS instrument,correlation analysis and the standards analysis.Three hourly and daily scenarios were considered,and the hierarchical parameter setting was further optimized by field application.The hourly and daily assessments revealed the evaluation factors for the discriminability of different air quality levels,practiced value for regional air quality improvement,and the reservation of general dominant pollutants.Finally,the universality testing in ZPIP successfully recognized most of the peaks,with 54.76%,38.39%and 6.85%for O_(3),VOCs and NO_(2) as the dominant pollutant,and reflected the daily ambient air quality condition,togetherwith the dominant pollutant.The AQI-V systemwith VOCs sub-index is essential for air quality evaluation in industrial parks,which can further provide scientific support to control the pollution of VOCs and the secondary pollutant,therefore significantly improve the air quality in local industrial parks.展开更多
Light-emission devices based on In Ga N/Ga N quantum well(QW)bring about an ongoing revolution in general lighting.One of the highly deliberated discussions in this field is the steep efficiency drop with the increasi...Light-emission devices based on In Ga N/Ga N quantum well(QW)bring about an ongoing revolution in general lighting.One of the highly deliberated discussions in this field is the steep efficiency drop with the increasing indium content of In Ga N/Ga N QW,posing a critical challenge to In Ga N-based long-wavelength optoelectronic devices.Unfortunately,the factors that underlie the limitation remain unclear.Here,by using femtosecond transient absorption spectroscopy,we investigate the carrier dynamics of In Ga N/Ga N QW and find that the luminescence efficiency of In Ga N/Ga N QW is closely related to the localization states(LSs),i.e.,dot-like In-rich In Ga N clusters,in the In Ga N layer.We demonstrate that the increase in the indium content can not only decrease the potential depth of LSs to weaken the localization binding effect and enhance the possibility of electrons being trapped by defects,but also enhance the density of LSs to increase the recombination channels and enlarge the full width at half maximum of the luminescence spectra.With these findings,we propose a model of carrier dynamics to deeply understand the emission mechanisms of In Ga N/Ga N QW,paving a way towards realizing highperformance In Ga N-based optoelectronic devices.展开更多
基金the financial support from the National Natural Science Foundation of China (Nos.U23A20677,22022610 and 52400137)"Pioneer" and "Leading Goose" R&D Program of Zhejiang (Nos.2022C03146 and 2023C03017)+2 种基金China Postdoctoral Science Foundation (No.2024T170805)Zhejiang Provincial Natural Science Foundation of China (No.LDT23E06015B06)the support of the Research Computing Center in College of Chemical and Biological Engineering at Zhejiang University for assistance with the calculations。
文摘Cuprous oxide(Cu_(2)O) is one of the most promising catalysts for electrochemical conversion of CO_(2) into value-added C_(2) products.The efficiency of CO_(2)-to-C_(2) conversion is highly dependent on the Cu_(2)O crystal plane orientation and the corresponding adsorbed ^(*)CO species.Herein,we constructed high-index crystal planes(311) in Cu_(2)O(CO-Cu_(2)O) via a facile self-selective CO-induced strategy under a CO atmosphere,which was verified by high-resolution transmission electron microscopy(HR-TEM) and atomic force microscopy(AFM) results.By exploiting the high surface energy of the high index crystal planes,^(*)CO species are stabilized in CO-Cu_(2)O during CO_(2)RR,resulting in exceptional catalytic performance for CO_(2)-to-C_(2)products.In situ infrared spectroscopy revealed that both atop-type(^(*)CO_(atop)) and hollow-type(^(*)CO_(hollow)) adsorption of ^(*)CO species occurred on the CO-Cu_(2)O.The asymmetric C-C coupling energy barrier between ^(*)CO_(atop) and ^(*)CO_(hollow) in(311) crystal plane decreases by 47.8 % compared to the symmetric coupling of ^(*)CO_(atop) in conventional(100) crystal planes.Consequently,the Faradaic efficiency of C_(2) products generated with CO-Cu_(2)O was increased by as high as 100 % compared to that with pristine Cu_(2)O.
基金supported by the National Key Research and Development Program of China (Nos.2022YFC3702000 and 2022YFC3703500)the Key R&D Project of Zhejiang Province (No.2022C03146).
文摘Severe ground-level ozone(O_(3))pollution over major Chinese cities has become one of the most challenging problems,which have deleterious effects on human health and the sustainability of society.This study explored the spatiotemporal distribution characteristics of ground-level O_(3) and its precursors based on conventional pollutant and meteorological monitoring data in Zhejiang Province from 2016 to 2021.Then,a high-performance convolutional neural network(CNN)model was established by expanding the moment and the concentration variations to general factors.Finally,the response mechanism of O_(3) to the variation with crucial influencing factors is explored by controlling variables and interpolating target variables.The results indicated that the annual average MDA8-90th concentrations in Zhejiang Province are higher in the northern and lower in the southern.When the wind direction(WD)ranges from east to southwest and the wind speed(WS)ranges between 2 and 3 m/sec,higher O_(3) concentration prone to occur.At different temperatures(T),the O_(3) concentration showed a trend of first increasing and subsequently decreasing with increasing NO_(2) concentration,peaks at the NO_(2) concentration around 0.02mg/m^(3).The sensitivity of NO_(2) to O_(3) formation is not easily affected by temperature,barometric pressure and dew point temperature.Additionally,there is a minimum IRNO_(2) at each temperature when the NO_(2) concentration is 0.03 mg/m^(3),and this minimum IRNO_(2) decreases with increasing temperature.The study explores the response mechanism of O_(3) with the change of driving variables,which can provide a scientific foundation and methodological support for the targeted management of O_(3) pollution.
基金supported by“Pioneer”and“Leading Goose”R&D Program of Zhejiang(Nos.2022C03146 and 2023C03017)the National Natural Science Foundation of China(Nos.U23A20677 and 22022610)+1 种基金Zhejiang Provincial Natural Science Foundation of China(No.LDT23E06015B06)the National Funded Postdoctoral Researcher Program of China(No.GZC20232363).
文摘The electrochemical carbon dioxide reduction reaction(CO_(2)RR)to high value-added fuels or chemicals driven by the renewable energy is promising to alleviate global warming.However,the selective CO_(2)reduction to C_(2)products remains challenge.Cu-based catalyst with the specific Cu^(0)and Cu^(+)sites is important to generate C_(2)products.This work used nitrogen(N)to tune amounts of Cu^(0)and Cu^(+)sites in Cu_(2)O catalysts and improve C_(2)-product conversion.The controllable Cu^(0)/Cu^(+)ratio of Cu_(2)O catalyst from 0.16 to 15.19 was achieved by adjusting the N doping amount using NH3/Ar plasma treatment.The major theme of this work was clarifying a volcano curve of the ethylene Faraday efficiency as a function of the Cu^(0)/Cu^(+)ratio.The optimal Cu^(0)/Cu^(+)ratio was determined as 0.43 for selective electroreduction CO_(2)to ethylene.X-ray spectroscopy and density functional theory(DFT)calculations were employed to elucidate that the strong interaction between N and Cu increased the binding energy of N–Cu bond and stabilize Cu^(+),resulting in a 92.3%reduction in the potential energy change for^(∗)CO-^(∗)CO dimerization.This study is inspiring in designing high performance electrocatalysts for CO_(2)conversion.
基金This work was supported by the National Key R&D Program of China(Nos.2022YFB3605205,2021YFB3601000,and 2021YFB3601002)the National Natural Science Foundation of China(Nos.U22A20134,62074069,62104078,and 62104079)the Science and Technology Developing Project of Jilin Province(Nos.20220201065GX,20230101053JC,and 20220101119JC).
文摘A nitrogen-polarity(N-polarity)GaN-based high electron mobility transistor(HEMT)shows great potential for high-fre-quency solid-state power amplifier applications because its two-dimensional electron gas(2DEG)density and mobility are mini-mally affected by device scaling.However,the Schottky barrier height(SBH)of N-polarity GaN is low.This leads to a large gate leakage in N-polarity GaN-based HEMTs.In this work,we investigate the effect of annealing on the electrical characteristics of N-polarity GaN-based Schottky barrier diodes(SBDs)with Ni/Au electrodes.Our results show that the annealing time and tem-perature have a large influence on the electrical properties of N-polarity GaN SBDs.Compared to the N-polarity SBD without annealing,the SBH and rectification ratio at±5 V of the SBD are increased from 0.51 eV and 30 to 0.77 eV and 7700,respec-tively,and the ideal factor of the SBD is decreased from 1.66 to 1.54 after an optimized annealing process.Our analysis results suggest that the improvement of the electrical properties of SBDs after annealing is mainly due to the reduction of the inter-face state density between Schottky contact metals and N-polarity GaN and the increase of barrier height for the electron emis-sion from the trap state at low reverse bias.
基金supported by Key Research and Development Program of Zhejiang Province (2021C03178, 2021C03165)。
文摘Volatile organic compound(VOC) emission control and source apportionment in small-scale industrial areas have become key topics of air pollution control in China. This study proposed a novel characteristic factor and pattern recognition(CF-PR) model for VOC source apportionment based on the similarity of characteristic factors between sources and receptors.A simulation was carried out in a typical industrial area with the CF-PR model involving simulated receptor samples. Refined and accurate source profiles were constructed through in situ sampling and analysis, covering rubber, chemicals, coating, electronics, plastics, printing, incubation and medical treatment industries. Characteristic factors of n-undecane,styrene, o-xylene and propane were identified. The source apportionment simulation results indicated that the predicted contribution rate was basically consistent with the real contribution rate. Compared to traditional receptor models, this method achieves notable advantages in terms of refinement and timeliness at similar accuracy, which is more suitable for VOC source identification and apportionment in small-scale industrial areas.
基金supported by the Key Research and Development Program of Zhejiang Province(Nos.2021C03165,2021C03178)the public welfare project of Zhejiang Province Grant numbers(No.LGF21B060002).
文摘Volatile organic compounds(VOCs)are the dominant pollutants in industrial parks.However,they are not generally considered as part of the air quality index(AQI)system,which leads to a biased assessment of pollution in industrial parks.In this study,a supplementary assessment system of AQI-V was established by analyzing VOCs characteristics with vehicle-mounted PTR-TOFMS instrument,correlation analysis and the standards analysis.Three hourly and daily scenarios were considered,and the hierarchical parameter setting was further optimized by field application.The hourly and daily assessments revealed the evaluation factors for the discriminability of different air quality levels,practiced value for regional air quality improvement,and the reservation of general dominant pollutants.Finally,the universality testing in ZPIP successfully recognized most of the peaks,with 54.76%,38.39%and 6.85%for O_(3),VOCs and NO_(2) as the dominant pollutant,and reflected the daily ambient air quality condition,togetherwith the dominant pollutant.The AQI-V systemwith VOCs sub-index is essential for air quality evaluation in industrial parks,which can further provide scientific support to control the pollution of VOCs and the secondary pollutant,therefore significantly improve the air quality in local industrial parks.
基金National Natural Science Foundation of China(62027822,U22A20134,62474080,U24A20300)National Key Research and Development Program of China(2021YFB3601002,2022YFB3605205,2024YFB3613900)Jilin Provincial Scientific and Technological Development Program(XXX202402001)。
文摘Light-emission devices based on In Ga N/Ga N quantum well(QW)bring about an ongoing revolution in general lighting.One of the highly deliberated discussions in this field is the steep efficiency drop with the increasing indium content of In Ga N/Ga N QW,posing a critical challenge to In Ga N-based long-wavelength optoelectronic devices.Unfortunately,the factors that underlie the limitation remain unclear.Here,by using femtosecond transient absorption spectroscopy,we investigate the carrier dynamics of In Ga N/Ga N QW and find that the luminescence efficiency of In Ga N/Ga N QW is closely related to the localization states(LSs),i.e.,dot-like In-rich In Ga N clusters,in the In Ga N layer.We demonstrate that the increase in the indium content can not only decrease the potential depth of LSs to weaken the localization binding effect and enhance the possibility of electrons being trapped by defects,but also enhance the density of LSs to increase the recombination channels and enlarge the full width at half maximum of the luminescence spectra.With these findings,we propose a model of carrier dynamics to deeply understand the emission mechanisms of In Ga N/Ga N QW,paving a way towards realizing highperformance In Ga N-based optoelectronic devices.
