分别以NO_3^-和NO-2为氮源,在9个不同N/S值条件下进行厌氧脱氮除硫试验。结果表明:当N/S值>0.67时,硝酸盐体系的出水硫化物浓度均小于1.0 mg/L,硫化物去除率达99%,脱硫速度明显高于亚硝酸盐体系,即N_3^-是脱硫最佳的电子受体。硫化...分别以NO_3^-和NO-2为氮源,在9个不同N/S值条件下进行厌氧脱氮除硫试验。结果表明:当N/S值>0.67时,硝酸盐体系的出水硫化物浓度均小于1.0 mg/L,硫化物去除率达99%,脱硫速度明显高于亚硝酸盐体系,即N_3^-是脱硫最佳的电子受体。硫化物加速了对NO-2的去除,即使将N/S值提高为4,对NO-2的去除率仍高达99%,硫化物是去除NO-2适宜的电子供体。硝酸盐体系的出水单质硫浓度明显高于亚硝酸盐体系,亚硝酸盐不利于单质硫富集。硝酸盐体系的N/S值从0.2增大为1时,大部分的N_3^-被转化为N2(产生氮气14~58 m L);而当硫化物不足时(N/S值从1继续增大为4),NO_3^-不能被全部转化为N2。对于亚硝酸盐体系而言,去除的NO-2基本全部生成N2。当NO-2受限时(N/S值<0.4)产生了大量的N2(48 m L),此时部分进水氨氮可能被去除。硝酸盐、亚硝酸盐体系中,硫化物过量时(N/S值=0.2),电子数的差均较高,分别为59%和66%;二者分别在N/S值为1、2时,电子数的差为零,电子得失达到平衡。展开更多
如何采用无酸工艺合成高性能超级电容器(SCs)用多孔炭纳米片电极材料是一个大的挑战。本文报道了一种简便且无酸的由煤焦油沥青(CTP)构建N/S共掺杂相互连接的多孔炭纳米片(NS-IPCNs)的新方法。制备的NS-IPCN_(800)具有相互连接的三维结...如何采用无酸工艺合成高性能超级电容器(SCs)用多孔炭纳米片电极材料是一个大的挑战。本文报道了一种简便且无酸的由煤焦油沥青(CTP)构建N/S共掺杂相互连接的多孔炭纳米片(NS-IPCNs)的新方法。制备的NS-IPCN_(800)具有相互连接的三维结构,这些三维结构由含有大量分级孔的二维炭纳米片组成。其中,丰富的微孔增加了离子吸附所需的活性位点,而短的中孔为离子传输提供了通道。此外,相互连接的三维结构为电子的快速传递提供了通道;掺杂的杂原子为NS-IPCNs电极提供了额外的赝电容。受益于这些优点,NS-IPCN_(800)电极在6 mol L^(−1) KOH电解液中,在0.05 A g^(−1)电流密度下的比电容达302 F g^(−1)。另外,NS-IPCN_(800)电容器在功率密度为25.98 W kg^(−1)下其能量密度达9.71 Wh kg^(−1)。更重要的是,NS-IPCN_(800)电容器在10000次循环充放电后电容保持率为94.2%,表现出优异的循环稳定性。这项工作为由CTP构建高性能储能装置用NS-IPCNs开辟了一种危害较小的策略。展开更多
Carbonaceous materials have drawn much attention in potassium-ion batteries (PIBs) due to their low price and superior physicochemical properties. However, the application of carbonaceous materials in PIB anodes is hi...Carbonaceous materials have drawn much attention in potassium-ion batteries (PIBs) due to their low price and superior physicochemical properties. However, the application of carbonaceous materials in PIB anodes is hindered by sluggish kinetics and large volume expansion. Herein, N/S co-doped carbon nanocapsule (NSCN) is constructed for superior K+ storage. The NSCN possesses 3D nanocapsule framework with abundant meso/macropores, which guarantees structural robustness and accelerates ions/electrons transportation. The high-level N/S co-doping in carbon matrix not only generates ample defects and active sites for K+ adsorption, but also expands interlayer distance for facile K+ intercalation/deintercalation. As a result, the NSCN electrode delivers a high reversible capacity (408 mAh g^(−1) at 0.05 A g^(−1)), outstanding rate capability (149 mAh g^(−1) at 5 A g^(−1)) and favorable cycle stability (150m Ah g^(−1) at 2 A g^(−1) after 2000 cycles). Ex situ TEM, Raman and XPS measurements demonstrate the excellent stability and reversibility of NSCN electrode during potassiation/depotassiation process. This work provides inspiration for the optimization of energy storage materials by structure and doping engineering.展开更多
Carbon-based materials have become a research hotspot in the field of energy storage devices in recent years due to their abundant resources,low cost,and environmental friendliness.However,the low capacity and poor hi...Carbon-based materials have become a research hotspot in the field of energy storage devices in recent years due to their abundant resources,low cost,and environmental friendliness.However,the low capacity and poor high rate performance still constitute great challenges.Metal organic framework-derived carbon has been widely researched because of its high porosity,tunable structure,and good conductivity.In this work,N/S codoped hierarchical porous carbon microspheres were prepared by a high-temperature heat treatment and atomic doping process using a zinc-based organic framework as the precursor.When used as a potassium-ion battery anode,it has a high reversible specific capacity(435.7 mAh g^(-1)),good rate performance(133.5 mAh g^(-1)at 10,000 m A g^(-1)),and long-term cycling stability(73.2%capacity retention after the 2500th cycle).The potassium storage mechanism of the derived carbon was explained by various electrochemical analysis methods and microstructure characterization techniques,and the relationship between the structural characteristics and electrochemical properties was researched.In a supercapacitor,the porous carbon material exhibits a specific capacitance of 307.2 F g^(-1)at a current density of 0.2 A g^(-1)in a KOH aqueous solution and achieves a retention rate of 99.88%after 10,000 cycles.The assembled symmetric supercapacitor device delivers a high energy density of 6.69 Wh kg^(-1),with a corresponding power density of 2500 W kg^(-1).In addition,density functional theory calculations further confirmed that N/S codoping can improve the adsorption capacities of potassium and hydroxyl ions in the derived carbon.展开更多
Developing high-performance non-precious metal electrocatalysts for oxygen reduction reaction(ORR)is crucial for the commercialization of fuel cells and metal-air batteries.However,doped carbon-based materials only sh...Developing high-performance non-precious metal electrocatalysts for oxygen reduction reaction(ORR)is crucial for the commercialization of fuel cells and metal-air batteries.However,doped carbon-based materials only show good ORR activity in alkaline medium,and become less effective in acidic environment.We believe that an appropriate combination of both ionic and electronic transport path,and well dopant distribution of doped carbon-based materials would help to realize high ORR performance un-der both acidic and alkaline cond让ions.Accordingly,a nitrogen and sulfur co-doped carbon framework with hierarchical through-hole structure is fabricated by morphology-controlled solid-state pyrolysis of poly(aniline-co-2-ami no thiophenol)foam.The uniform high concentrations of nitrogen and sulfur,high intrinsic conductivity,and integrated three dimensional ionic and electronic transfer passageways of the 3D porous structure lead to synergistic effects in catalyzing ORR.As a result,the limiting current density of the carbonized poly(aniline-co-2-aminothiophenol)foam is equivalent to commercial Pt/C in acidic environment,and twice the latter in alkaline medium.展开更多
针对近连续流过渡区多尺度绕流问题,学界发展了N-S(Navier-Stokes)/DSMC(direct simulation Monte Carlo)耦合方法,大多数此类求解器面临着耦合界面波动失稳的难题,因此对复杂外形和耦合界面的通用性值得重点研究。鉴于非结构网格面向...针对近连续流过渡区多尺度绕流问题,学界发展了N-S(Navier-Stokes)/DSMC(direct simulation Monte Carlo)耦合方法,大多数此类求解器面临着耦合界面波动失稳的难题,因此对复杂外形和耦合界面的通用性值得重点研究。鉴于非结构网格面向复杂外形高度的贴体性、优良适应性以及工程领域对过渡流区高效通用型计算方法的需求,提出并实现了一套三维复杂界面四面体非结构网格N-S/DSMC耦合方法用于模拟高超声速过渡流。该方法使用局部克努森数作为连续失效参数划分连续/稀薄区域,并生成三维复杂N-S/DSMC耦合界面,沿分界面两侧分别推进一层或多层界面信息传递单元,基于边界状态法进行信息耦合。该耦合方法无需对复杂不规则分界面作光滑和修型处理,具备对复杂过渡流区工程问题数值模拟的通用性。分别对三维高超声速圆球和钝锥绕流进行模拟,数值结果显示:与参考文献中的DSMC方法相比,激波处数值和壁面特征值基本一致,最大误差不超过8%,但计算效率分别提高了1.74倍和2.28倍,验证了该耦合方法的正确性和高效性。展开更多
文摘分别以NO_3^-和NO-2为氮源,在9个不同N/S值条件下进行厌氧脱氮除硫试验。结果表明:当N/S值>0.67时,硝酸盐体系的出水硫化物浓度均小于1.0 mg/L,硫化物去除率达99%,脱硫速度明显高于亚硝酸盐体系,即N_3^-是脱硫最佳的电子受体。硫化物加速了对NO-2的去除,即使将N/S值提高为4,对NO-2的去除率仍高达99%,硫化物是去除NO-2适宜的电子供体。硝酸盐体系的出水单质硫浓度明显高于亚硝酸盐体系,亚硝酸盐不利于单质硫富集。硝酸盐体系的N/S值从0.2增大为1时,大部分的N_3^-被转化为N2(产生氮气14~58 m L);而当硫化物不足时(N/S值从1继续增大为4),NO_3^-不能被全部转化为N2。对于亚硝酸盐体系而言,去除的NO-2基本全部生成N2。当NO-2受限时(N/S值<0.4)产生了大量的N2(48 m L),此时部分进水氨氮可能被去除。硝酸盐、亚硝酸盐体系中,硫化物过量时(N/S值=0.2),电子数的差均较高,分别为59%和66%;二者分别在N/S值为1、2时,电子数的差为零,电子得失达到平衡。
文摘如何采用无酸工艺合成高性能超级电容器(SCs)用多孔炭纳米片电极材料是一个大的挑战。本文报道了一种简便且无酸的由煤焦油沥青(CTP)构建N/S共掺杂相互连接的多孔炭纳米片(NS-IPCNs)的新方法。制备的NS-IPCN_(800)具有相互连接的三维结构,这些三维结构由含有大量分级孔的二维炭纳米片组成。其中,丰富的微孔增加了离子吸附所需的活性位点,而短的中孔为离子传输提供了通道。此外,相互连接的三维结构为电子的快速传递提供了通道;掺杂的杂原子为NS-IPCNs电极提供了额外的赝电容。受益于这些优点,NS-IPCN_(800)电极在6 mol L^(−1) KOH电解液中,在0.05 A g^(−1)电流密度下的比电容达302 F g^(−1)。另外,NS-IPCN_(800)电容器在功率密度为25.98 W kg^(−1)下其能量密度达9.71 Wh kg^(−1)。更重要的是,NS-IPCN_(800)电容器在10000次循环充放电后电容保持率为94.2%,表现出优异的循环稳定性。这项工作为由CTP构建高性能储能装置用NS-IPCNs开辟了一种危害较小的策略。
基金the financial supports from the National Natural Science Foundation of China(Grant Nos.51872005,U1508201,52072002)。
文摘Carbonaceous materials have drawn much attention in potassium-ion batteries (PIBs) due to their low price and superior physicochemical properties. However, the application of carbonaceous materials in PIB anodes is hindered by sluggish kinetics and large volume expansion. Herein, N/S co-doped carbon nanocapsule (NSCN) is constructed for superior K+ storage. The NSCN possesses 3D nanocapsule framework with abundant meso/macropores, which guarantees structural robustness and accelerates ions/electrons transportation. The high-level N/S co-doping in carbon matrix not only generates ample defects and active sites for K+ adsorption, but also expands interlayer distance for facile K+ intercalation/deintercalation. As a result, the NSCN electrode delivers a high reversible capacity (408 mAh g^(−1) at 0.05 A g^(−1)), outstanding rate capability (149 mAh g^(−1) at 5 A g^(−1)) and favorable cycle stability (150m Ah g^(−1) at 2 A g^(−1) after 2000 cycles). Ex situ TEM, Raman and XPS measurements demonstrate the excellent stability and reversibility of NSCN electrode during potassiation/depotassiation process. This work provides inspiration for the optimization of energy storage materials by structure and doping engineering.
基金supported by the National Natural Science Foundation of China (51764029, 52004116)the National Key Research and Development Program of China (2019YFC1803501)+1 种基金the Applied Basic Research Plan of Yunnan Province(202001AU070039, 2018FB087)the Science Research Foundation of Yunnan Provincial Department of Education (2020J0070)
文摘Carbon-based materials have become a research hotspot in the field of energy storage devices in recent years due to their abundant resources,low cost,and environmental friendliness.However,the low capacity and poor high rate performance still constitute great challenges.Metal organic framework-derived carbon has been widely researched because of its high porosity,tunable structure,and good conductivity.In this work,N/S codoped hierarchical porous carbon microspheres were prepared by a high-temperature heat treatment and atomic doping process using a zinc-based organic framework as the precursor.When used as a potassium-ion battery anode,it has a high reversible specific capacity(435.7 mAh g^(-1)),good rate performance(133.5 mAh g^(-1)at 10,000 m A g^(-1)),and long-term cycling stability(73.2%capacity retention after the 2500th cycle).The potassium storage mechanism of the derived carbon was explained by various electrochemical analysis methods and microstructure characterization techniques,and the relationship between the structural characteristics and electrochemical properties was researched.In a supercapacitor,the porous carbon material exhibits a specific capacitance of 307.2 F g^(-1)at a current density of 0.2 A g^(-1)in a KOH aqueous solution and achieves a retention rate of 99.88%after 10,000 cycles.The assembled symmetric supercapacitor device delivers a high energy density of 6.69 Wh kg^(-1),with a corresponding power density of 2500 W kg^(-1).In addition,density functional theory calculations further confirmed that N/S codoping can improve the adsorption capacities of potassium and hydroxyl ions in the derived carbon.
基金financial support by the National Natural Science Foundation of China (Grant: 51333008)Young Teacher Training Program of Sun Yat-sen University (Grant: 17lgpy86)
文摘Developing high-performance non-precious metal electrocatalysts for oxygen reduction reaction(ORR)is crucial for the commercialization of fuel cells and metal-air batteries.However,doped carbon-based materials only show good ORR activity in alkaline medium,and become less effective in acidic environment.We believe that an appropriate combination of both ionic and electronic transport path,and well dopant distribution of doped carbon-based materials would help to realize high ORR performance un-der both acidic and alkaline cond让ions.Accordingly,a nitrogen and sulfur co-doped carbon framework with hierarchical through-hole structure is fabricated by morphology-controlled solid-state pyrolysis of poly(aniline-co-2-ami no thiophenol)foam.The uniform high concentrations of nitrogen and sulfur,high intrinsic conductivity,and integrated three dimensional ionic and electronic transfer passageways of the 3D porous structure lead to synergistic effects in catalyzing ORR.As a result,the limiting current density of the carbonized poly(aniline-co-2-aminothiophenol)foam is equivalent to commercial Pt/C in acidic environment,and twice the latter in alkaline medium.
文摘针对近连续流过渡区多尺度绕流问题,学界发展了N-S(Navier-Stokes)/DSMC(direct simulation Monte Carlo)耦合方法,大多数此类求解器面临着耦合界面波动失稳的难题,因此对复杂外形和耦合界面的通用性值得重点研究。鉴于非结构网格面向复杂外形高度的贴体性、优良适应性以及工程领域对过渡流区高效通用型计算方法的需求,提出并实现了一套三维复杂界面四面体非结构网格N-S/DSMC耦合方法用于模拟高超声速过渡流。该方法使用局部克努森数作为连续失效参数划分连续/稀薄区域,并生成三维复杂N-S/DSMC耦合界面,沿分界面两侧分别推进一层或多层界面信息传递单元,基于边界状态法进行信息耦合。该耦合方法无需对复杂不规则分界面作光滑和修型处理,具备对复杂过渡流区工程问题数值模拟的通用性。分别对三维高超声速圆球和钝锥绕流进行模拟,数值结果显示:与参考文献中的DSMC方法相比,激波处数值和壁面特征值基本一致,最大误差不超过8%,但计算效率分别提高了1.74倍和2.28倍,验证了该耦合方法的正确性和高效性。
