Carbon-supported transition metal single atoms are promising oxygen reduction reaction(ORR)electrocatalyst.Since there are many types of carbon supports and transition metals,the accurate prediction of the components ...Carbon-supported transition metal single atoms are promising oxygen reduction reaction(ORR)electrocatalyst.Since there are many types of carbon supports and transition metals,the accurate prediction of the components with high activity through theoretical calculations can greatly save experimental time and costs.In this work,the ORR catalytic properties of 180 types single-atom catalysts(SACs)composed of the eight representative carbon-based substrates(graphdiyne,C_(2)N,C_(3)N_(4),phthalocyanine,C-coordination graphene,N-coordination graphene,covalent organic frameworks and metal-organic frameworks)and 3d,4d,and 5d transition metal elements are investigated by density functional theory(DFT).The adsorption free energy of OH^(*) is proved a universal descriptor capable of accurately prediction of the ORR catalytic activity.It is found that the oxygen reduction reaction overpotentials of all the researched SACs follow one volcano shape very well with the adsorption free energy of OH^(*).Phthalocyanine,N-coordination graphene and metal-organic frameworks stand out as the promising supports for single metal atom due to the relatively lower overpotentials.Notably,the Co-doped metal-organic frameworks,Ir-doped phthalocyanine,Co-doped N-coordination graphene,Co-doped graphdiyne and Rh-doped phthalocyanine show extremely low overpotentials comparable to that of Pt(111).The study provides a guideline for design and selection of carbon-supported SACs toward oxygen reduction reaction.展开更多
Urban tree inventory is a great tool for gathering data that can be used by different end users. This study attempted to chart the species diversity in planted areas and measure their tree diameter at breast height to...Urban tree inventory is a great tool for gathering data that can be used by different end users. This study attempted to chart the species diversity in planted areas and measure their tree diameter at breast height to screen them for the carbon storage potential. A total of 2860 trees belonging to 36 species were recorded in the planted vegetation in parks and avenue plantation. The dominant species were Azadirachta indicia (25.5%), Conocarpus erectus (19.2%), Ficus spp. (15.5%), Tabebuia rosea (9.2%), Peitophorum pterocarpum (9.0%) and the remaining represents (21.6%) of the tree identified in this study. It was found that the highest contribution of carbon sequestration (CO<sub>2</sub> equivalent) is dominated by the Ficus spp. (30.3%) with a total of 3399.3 tCO<sub>2</sub>eq, followed by Azadirachta indicia (25.4%) with a total of 2845.2 tCO<sub>2</sub>eq and Conocarpus erectus (20.4%) with a total of 2286 tCO<sub>2</sub>eq. The entire area has the capability to sequester around 11,213.3 tCO<sub>2</sub>eq and on average of 3.9 ± 0.1 tCO<sub>2</sub>eq. In accordance with the findings, it is imperative for the preservation of a sustainable environment to have vegetation that has the capacity to store carbon. The study suggests, there is potential to increase carbon sequestration in urban cities through plantation programs on existing and new land uses and along roads.展开更多
The catalyst screening tests for carbon dioxide oxidative coupling of methane (CO2-OCM) have been investigated over ternary and binary metal oxide catalysts. The catalysts are prepared by doping MgO- and CeO2-based so...The catalyst screening tests for carbon dioxide oxidative coupling of methane (CO2-OCM) have been investigated over ternary and binary metal oxide catalysts. The catalysts are prepared by doping MgO- and CeO2-based solids with oxides from alkali (Li2O), alkaline earth (CaO), and transition metal groups (WO3 or MnO). The presence of the peroxide (O2-2) active sites on the Li2O2, revealed by Raman spectroscopy, may be the key factor in the enhanced performance of some of the Li2O/MgO catalysts. The high reducibility of the CeO2 catalyst, an important factor in the CO2-OCM catalyst activity, may be enhanced by the presence of manganese oxide species. The manganese oxide species increases oxygen mobility and oxygen vacancies in the CeO2 catalyst. Raman and Fourier Transform Infra Red (FT-IR) spectroscopies revealed the presence of lattice vibrations of metal-oxygen bondings and active sites in which the peaks corresponding to the bulk crystalline structures of Li2O, CaO, WO3 and MnO are detected. The performance of 5%MnO/15%CaO/CeO2 catalyst is the most potential among the CeO2-based catalysts, although lower than the 2%Li2O/MgO catalyst. The 2%Li2O/MgO catalyst showed the most promising C2+ hydrocarbons selectivity and yield at 98.0% and 5.7%, respectively.展开更多
基于2020年1-12月苏州城区近地面大气CO_(2)浓度连续观测数据,采用基于稳健局部近似回归的筛分方法(robust extraction of baseline signal,REBS)对观测数据进行筛分,对比本底和非本底CO_(2)体积浓度分布特征,分析CO_(2)与污染物浓度的...基于2020年1-12月苏州城区近地面大气CO_(2)浓度连续观测数据,采用基于稳健局部近似回归的筛分方法(robust extraction of baseline signal,REBS)对观测数据进行筛分,对比本底和非本底CO_(2)体积浓度分布特征,分析CO_(2)与污染物浓度的相关性和不同季节、不同风向下的CO_(2)体积浓度水平。结果表明:2020年苏州城区CO_(2)体积浓度水平高出瓦里关背景站0.273×10^(-4),与北京、西安、上海和临汾相当。CO_(2)体积浓度冬季高,夏季低;本底浓度日变化特征为单峰,峰值和谷值分别出现在7:00和16:00,吸收浓度为双峰分布,峰值分别出现在4:00-6:00和20:00,谷值出现在15:00。抬升浓度受局地污染源影响较大,日变化特征不明显。本底CO_(2)体积浓度与PM2.5、NO2和CO浓度相关性系数分别为0.495、0.461和0.330,非本底CO_(2)体积浓度与其他污染物浓度相关性高于本底CO_(2)体积浓度,表明局地交通排放源对CO_(2)浓度影响显著。春夏季CO_(2)体积浓度受本地排放和西北方向输送共同影响,秋冬季偏西和偏北方向区域输送贡献更大。展开更多
Adsorption-based carbon capture has been recognized as an attractive method for mitigating global warming.Metal–organic frameworks(MOFs)are promising candidate adsorbents for this purpose due to their high adsorption...Adsorption-based carbon capture has been recognized as an attractive method for mitigating global warming.Metal–organic frameworks(MOFs)are promising candidate adsorbents for this purpose due to their high adsorption uptake and selectivity for carbon dioxide.However,in real-world applications,such as direct air capture,the presence of moisture in the feed gas may pose a grand challenge for CO_(2)adsorption in MOFs.This paper aims to address the issue of water–CO_(2)co-adsorption in MOFs and present screening criteria for selecting MOFs that preferentially adsorb CO_(2)under humid conditions.First,we uncover a comprehensive overview of CO_(2)–water co-adsorption characteristics of various MOFs.Then,the high-throughput screening methods are summarized.Both computational and experimental efforts have been dedicated to identify the promising MOFs for humid CO_(2)capture.According to the screening results and adsorption mechanism,the optimal preparation strategies are proposed tomodulate the effect of water on CO_(2)uptake in MOFs.Finally,current MOF-based CO_(2)capture prototypes are presented to evaluate their practical feasibility and performance.This work could offer valuable guidance for the development and application of MOFs for CO_(2)capture in the presence of water and inspire further research in this field.展开更多
We developed a new scheme to suppress the electric-field-screening effect in high growth density of a carbon nanotube(CNT) film during its intense pulsed emission.We synthesize the CNT film on a tridimensional surface...We developed a new scheme to suppress the electric-field-screening effect in high growth density of a carbon nanotube(CNT) film during its intense pulsed emission.We synthesize the CNT film on a tridimensional surface(t-CNT film).The tridimensional surface includes wet etched silicon pyramids,and the Ni layer is electroless plated thereon.The intense pulsed emission characteristics of the t-CNT and planar-grown CNT(p-CNT) films were measured using a diode structure in single-pulse mode.The even turn-on field decreased from 5.5 V/μm for p-CNTs to 2.8 V/m for t-CNTs,and the peak emission current increased from 232 A for p-CNTs to 324 A for t-CNTs at a peak field intensity ～12.2 V/m.The peak current of the t-CNT film increased by ～39.7% over the p-CNT film.It is clear that the micro-pyramid array can effectively suppress the field screening effect to improve the electron-emission of CNT films.展开更多
基金supported by the National Natural Science Foundation of China(No.51371017)。
文摘Carbon-supported transition metal single atoms are promising oxygen reduction reaction(ORR)electrocatalyst.Since there are many types of carbon supports and transition metals,the accurate prediction of the components with high activity through theoretical calculations can greatly save experimental time and costs.In this work,the ORR catalytic properties of 180 types single-atom catalysts(SACs)composed of the eight representative carbon-based substrates(graphdiyne,C_(2)N,C_(3)N_(4),phthalocyanine,C-coordination graphene,N-coordination graphene,covalent organic frameworks and metal-organic frameworks)and 3d,4d,and 5d transition metal elements are investigated by density functional theory(DFT).The adsorption free energy of OH^(*) is proved a universal descriptor capable of accurately prediction of the ORR catalytic activity.It is found that the oxygen reduction reaction overpotentials of all the researched SACs follow one volcano shape very well with the adsorption free energy of OH^(*).Phthalocyanine,N-coordination graphene and metal-organic frameworks stand out as the promising supports for single metal atom due to the relatively lower overpotentials.Notably,the Co-doped metal-organic frameworks,Ir-doped phthalocyanine,Co-doped N-coordination graphene,Co-doped graphdiyne and Rh-doped phthalocyanine show extremely low overpotentials comparable to that of Pt(111).The study provides a guideline for design and selection of carbon-supported SACs toward oxygen reduction reaction.
文摘Urban tree inventory is a great tool for gathering data that can be used by different end users. This study attempted to chart the species diversity in planted areas and measure their tree diameter at breast height to screen them for the carbon storage potential. A total of 2860 trees belonging to 36 species were recorded in the planted vegetation in parks and avenue plantation. The dominant species were Azadirachta indicia (25.5%), Conocarpus erectus (19.2%), Ficus spp. (15.5%), Tabebuia rosea (9.2%), Peitophorum pterocarpum (9.0%) and the remaining represents (21.6%) of the tree identified in this study. It was found that the highest contribution of carbon sequestration (CO<sub>2</sub> equivalent) is dominated by the Ficus spp. (30.3%) with a total of 3399.3 tCO<sub>2</sub>eq, followed by Azadirachta indicia (25.4%) with a total of 2845.2 tCO<sub>2</sub>eq and Conocarpus erectus (20.4%) with a total of 2286 tCO<sub>2</sub>eq. The entire area has the capability to sequester around 11,213.3 tCO<sub>2</sub>eq and on average of 3.9 ± 0.1 tCO<sub>2</sub>eq. In accordance with the findings, it is imperative for the preservation of a sustainable environment to have vegetation that has the capacity to store carbon. The study suggests, there is potential to increase carbon sequestration in urban cities through plantation programs on existing and new land uses and along roads.
文摘The catalyst screening tests for carbon dioxide oxidative coupling of methane (CO2-OCM) have been investigated over ternary and binary metal oxide catalysts. The catalysts are prepared by doping MgO- and CeO2-based solids with oxides from alkali (Li2O), alkaline earth (CaO), and transition metal groups (WO3 or MnO). The presence of the peroxide (O2-2) active sites on the Li2O2, revealed by Raman spectroscopy, may be the key factor in the enhanced performance of some of the Li2O/MgO catalysts. The high reducibility of the CeO2 catalyst, an important factor in the CO2-OCM catalyst activity, may be enhanced by the presence of manganese oxide species. The manganese oxide species increases oxygen mobility and oxygen vacancies in the CeO2 catalyst. Raman and Fourier Transform Infra Red (FT-IR) spectroscopies revealed the presence of lattice vibrations of metal-oxygen bondings and active sites in which the peaks corresponding to the bulk crystalline structures of Li2O, CaO, WO3 and MnO are detected. The performance of 5%MnO/15%CaO/CeO2 catalyst is the most potential among the CeO2-based catalysts, although lower than the 2%Li2O/MgO catalyst. The 2%Li2O/MgO catalyst showed the most promising C2+ hydrocarbons selectivity and yield at 98.0% and 5.7%, respectively.
文摘基于2020年1-12月苏州城区近地面大气CO_(2)浓度连续观测数据,采用基于稳健局部近似回归的筛分方法(robust extraction of baseline signal,REBS)对观测数据进行筛分,对比本底和非本底CO_(2)体积浓度分布特征,分析CO_(2)与污染物浓度的相关性和不同季节、不同风向下的CO_(2)体积浓度水平。结果表明:2020年苏州城区CO_(2)体积浓度水平高出瓦里关背景站0.273×10^(-4),与北京、西安、上海和临汾相当。CO_(2)体积浓度冬季高,夏季低;本底浓度日变化特征为单峰,峰值和谷值分别出现在7:00和16:00,吸收浓度为双峰分布,峰值分别出现在4:00-6:00和20:00,谷值出现在15:00。抬升浓度受局地污染源影响较大,日变化特征不明显。本底CO_(2)体积浓度与PM2.5、NO2和CO浓度相关性系数分别为0.495、0.461和0.330,非本底CO_(2)体积浓度与其他污染物浓度相关性高于本底CO_(2)体积浓度,表明局地交通排放源对CO_(2)浓度影响显著。春夏季CO_(2)体积浓度受本地排放和西北方向输送共同影响,秋冬季偏西和偏北方向区域输送贡献更大。
基金National Key Research and Development Program of China,Grant/Award Numbers:2022YFB4101700,2022YFE0128600National Natural Science Foundation of China,Grant/Award Numbers:52276022,22278365,22225802Basic Research Funds for the Central Government‘Innovative Team of Zhejiang University’,Grant/Award Number:2022FZZX01-09。
文摘Adsorption-based carbon capture has been recognized as an attractive method for mitigating global warming.Metal–organic frameworks(MOFs)are promising candidate adsorbents for this purpose due to their high adsorption uptake and selectivity for carbon dioxide.However,in real-world applications,such as direct air capture,the presence of moisture in the feed gas may pose a grand challenge for CO_(2)adsorption in MOFs.This paper aims to address the issue of water–CO_(2)co-adsorption in MOFs and present screening criteria for selecting MOFs that preferentially adsorb CO_(2)under humid conditions.First,we uncover a comprehensive overview of CO_(2)–water co-adsorption characteristics of various MOFs.Then,the high-throughput screening methods are summarized.Both computational and experimental efforts have been dedicated to identify the promising MOFs for humid CO_(2)capture.According to the screening results and adsorption mechanism,the optimal preparation strategies are proposed tomodulate the effect of water on CO_(2)uptake in MOFs.Finally,current MOF-based CO_(2)capture prototypes are presented to evaluate their practical feasibility and performance.This work could offer valuable guidance for the development and application of MOFs for CO_(2)capture in the presence of water and inspire further research in this field.
基金supported by the National Natural Science Foundation of China (51072184,50972132,51002143 and 60801022)the Aeronautical Science Foundation of China (2009ZE55003 and 2010ZF55013)the Basic and Advanced Technology Program of Henan (092300410139)
文摘We developed a new scheme to suppress the electric-field-screening effect in high growth density of a carbon nanotube(CNT) film during its intense pulsed emission.We synthesize the CNT film on a tridimensional surface(t-CNT film).The tridimensional surface includes wet etched silicon pyramids,and the Ni layer is electroless plated thereon.The intense pulsed emission characteristics of the t-CNT and planar-grown CNT(p-CNT) films were measured using a diode structure in single-pulse mode.The even turn-on field decreased from 5.5 V/μm for p-CNTs to 2.8 V/m for t-CNTs,and the peak emission current increased from 232 A for p-CNTs to 324 A for t-CNTs at a peak field intensity ～12.2 V/m.The peak current of the t-CNT film increased by ～39.7% over the p-CNT film.It is clear that the micro-pyramid array can effectively suppress the field screening effect to improve the electron-emission of CNT films.
