Developing high efficiency and low cost electrocatalysts is critical for the enhancement of oxygen reduction reaction(ORR),which is the fundamental for the development and commercialization of renewable energy convers...Developing high efficiency and low cost electrocatalysts is critical for the enhancement of oxygen reduction reaction(ORR),which is the fundamental for the development and commercialization of renewable energy conversion technology.Herein,zinc-nitrogen-carbon(Zn-N-C)was prepared by using biomass resource chitosan via a facile carbon bath method.The obtained Zn-N-C delivered a high specific surface area(794.7 cm^2/g)together with pore volume(0.49 cm^3/g).During the electrochemical evaluation of oxygen reduction reaction(ORR),Zn-N-C displayed high activity for ORR with an onset pote ntial E0=0.96 VRHE and a half wave potential E1/2=0.86 VRHE,which were more positive than those of the comme rcial 20 wt%Pt/C benchmark catalyst(E0=0.96 VRHE and E1/2=0.81 VRHE).In addition,the ZnN-C catalyst also had a better stability and methanol tolerance than those of the Pt/C catalyst.展开更多
The incorporation of straw in cultivated fields can potentially improve soil quality and crop yield. However, the presence of recalcitrant carbon compounds in straw slow its decomposition rate. The objective of this s...The incorporation of straw in cultivated fields can potentially improve soil quality and crop yield. However, the presence of recalcitrant carbon compounds in straw slow its decomposition rate. The objective of this study was to determine the effects of different nitrogen sources, with and without the application of zinc, on straw decomposition and soil quality. Soils were treated with three different nitrogen sources, with and without zinc: urea(CO(NH2)2), ammonium sulfate((NH4)2SO4), and ammonium chloride(NH4Cl). The combined treatments were as follows: maize(M) and wheat(W) straw incorporated into urea-, ammonium sulfate-, or ammonium chloride-treated soil(U, S, and C, respectively) with and without zinc(Z)(MU, MUZ, WU, WUZ; MS, MSZ, WS, WSZ; MC, MCZ, WC, WCZ, respectively); straw with zinc only(MZ, WZ); straw with untreated soil(MS, WS); and soil-only or control conditions(NT). The experiment consisted of 17 treatments with four replications. Each pot contained 150 g soil and 1.125 g straw, had a moisture content of 80% of the field capacity, and was incubated for 53 days at 25°C. The rates of CO2-C emission, cumulative CO2-C evolution, total CO2 production in the soils of different treatments were measured to infer decomposition rates. The total organic carbon(TOC), labile organic carbon(LOC), and soil microbial biomass in the soils of different treatments were measured to infer soil quality. All results were significantly different(P<0.05) with the exception of the labile organic carbon(LOC). The maize and wheat straw showed different patterns in CO2 evolution rates. For both straw types, Zn had a synergic effect with U, but an antagonistic effect with the other N sources as determined by the total CO2 produced. The MUZ treatment showed the highest decomposition rate and cumulative CO2 concentration(1 120.29 mg/pot), whereas the WACZ treatment had the lowest cumulative CO2 concentration(1 040.57 mg/pot). The addition of NH4 Cl resulted in the highest total organic carbon(TOC) concentration(11.59 mg kg-1). The incorporation of wheat straw resulted in higher microbial biomass accumulation in soils relative to that of the maize straw application. The results demonstrate that mineral N sources can affect the ability of microorganisms to decompose straw, as well as the soil carbon concentrations.展开更多
化石能源的过度消耗使开发新能源成为当务之急,燃料电池被认为是一种极具发展前景的高效能源转换装置.氧还原反应(ORR)和氧析出反应(OER)是燃料电池中至关重要的可逆氧电催化反应.由于氧反应的动力学迟缓,通常需要使用贵金属Pt和IrO_(2...化石能源的过度消耗使开发新能源成为当务之急,燃料电池被认为是一种极具发展前景的高效能源转换装置.氧还原反应(ORR)和氧析出反应(OER)是燃料电池中至关重要的可逆氧电催化反应.由于氧反应的动力学迟缓,通常需要使用贵金属Pt和IrO_(2)分别催化ORR和OER反应.但其储量有限、价格高,因此,亟待开发廉价高效的氧反应催化剂.Co_(9)S_(8)属于镍黄铁矿晶型,由于其具有特殊的d带结构,被认为是一种多功能的电催化剂.Co_(9)S_(8)具有Oh构型的八面体位点和扭曲的C3v四面体位点,S的配位场效应诱导Co_(9)S_(8)中八面体Co的未成对电子在较低的费米能级上分裂成t2g和eg能带.基于d带理论,d带中心向费米能级的靠近有利于反键轨道的填充和更强的键合,为进一步优化Co_(9)S_(8)的电子结构提供了思路.本文以间苯二酚、甲醛和正硅酸四乙酯进行液相自发成核反应,由于SiO_(2)球和酚醛树脂的聚合速率不同形成了RF@SiO_(2)封装结构.经过高温碳化和碱蚀刻后,酚醛树脂外壳发生碳化并塌陷,形成了碗状的氮掺杂空心碳球(NHCS).然后将铁原子引入到Co_(9)S_(8)中并锚定在空心碳球上,制备了不同铁含量的Fe_(x)Co_(9‒x)S_(8)-NHCS复合催化剂.铁既可以占据钴镍黄铁矿结构中的八面体位,也可以占据四面体位.表征结果表明,当铁钴的比例不超过1:8时,低自旋的Fe^(2+)首先占据八面体位点;当铁钴的比例超过1:8时,四面体位的Co也可以被高自旋的Fe^(2+)取代.XPS结果表明,在引入Fe^(2+)后,Fe_(x)Co_(9‒x)S_(8)-NHCS中的Co^(2+)峰和Co0峰位置都产生了明显的偏移,表明Fe^(2+)在八面体位的占位会影响到四面体位的Co原子,进而有可能影响到电化学性能.结合Fe_(x)Co_(9‒x)S_(8)-NHCS的ORR和OER性能测试结果和结构表征数据可以看出,当Fe原子的系数x由0增至1,此时Fe^(2+)发生八面体位取代,金属‒硫键的键长也相应增加,从而提高了电催化活性.当x由1增加到4.5,此时Fe^(2+)发生四面体位取代,电催化活性降低.因此,铁钴的比例为1:8的复合催化剂在0.1 mol/L KOH中表现出了较好的ORR(E1/2=0.80 V vs.RHE)和OER(Ej=10=1.53 V vs.RHE)双功能电催化性能.最后,将最优比的铁钴(铁钴的比例为1:8)复合催化剂应用于碱性的可充电锌空气电池和中性环境的微生物燃料电池.具有复合催化剂阴极的锌空气电池和微生物燃料电池都表现出高功率密度和较好的稳定性,证实本文所开发的催化剂具有较好的应用价值.综上,本文不仅提出了一种合成高效催化剂的新策略,也还为促进钴镍黄铁矿结构氧催化剂的发展提供了重要的启示.展开更多
Tomato is a common food on the human table. Up to now, the research on the growth and development model of tomato has been about 50 years. There are many researches on the main nutrients of tomato, such as carbon and ...Tomato is a common food on the human table. Up to now, the research on the growth and development model of tomato has been about 50 years. There are many researches on the main nutrients of tomato, such as carbon and nitrogen, but few on the trace element zinc. In this paper, taking plant nutrient C, N and Z<sub>n</sub> as variables, the differential equation model of C, N and Z<sub>n</sub> in tomato growth and development was established. According to the research of tomato as a whole and divided into root and leaf, the one-compartment and two-compartment models of tomato growth and development were established. The model was analyzed by Matlab program, and the existing experimental data was used to test the numerical simulation results, which proves that the model conforms to the facts.展开更多
基金supported by the National Natural Science Foundation of China(No.21865025)。
文摘Developing high efficiency and low cost electrocatalysts is critical for the enhancement of oxygen reduction reaction(ORR),which is the fundamental for the development and commercialization of renewable energy conversion technology.Herein,zinc-nitrogen-carbon(Zn-N-C)was prepared by using biomass resource chitosan via a facile carbon bath method.The obtained Zn-N-C delivered a high specific surface area(794.7 cm^2/g)together with pore volume(0.49 cm^3/g).During the electrochemical evaluation of oxygen reduction reaction(ORR),Zn-N-C displayed high activity for ORR with an onset pote ntial E0=0.96 VRHE and a half wave potential E1/2=0.86 VRHE,which were more positive than those of the comme rcial 20 wt%Pt/C benchmark catalyst(E0=0.96 VRHE and E1/2=0.81 VRHE).In addition,the ZnN-C catalyst also had a better stability and methanol tolerance than those of the Pt/C catalyst.
基金supported by the Key Technologies R&D Program of China during the 12th Five-Year Plan period(2012BAD14B11)the National Natural Science Foundation of China (41371288, 31071863)the Fundamental Research Funds for Northwest A&F University, China (QN2011074)
文摘The incorporation of straw in cultivated fields can potentially improve soil quality and crop yield. However, the presence of recalcitrant carbon compounds in straw slow its decomposition rate. The objective of this study was to determine the effects of different nitrogen sources, with and without the application of zinc, on straw decomposition and soil quality. Soils were treated with three different nitrogen sources, with and without zinc: urea(CO(NH2)2), ammonium sulfate((NH4)2SO4), and ammonium chloride(NH4Cl). The combined treatments were as follows: maize(M) and wheat(W) straw incorporated into urea-, ammonium sulfate-, or ammonium chloride-treated soil(U, S, and C, respectively) with and without zinc(Z)(MU, MUZ, WU, WUZ; MS, MSZ, WS, WSZ; MC, MCZ, WC, WCZ, respectively); straw with zinc only(MZ, WZ); straw with untreated soil(MS, WS); and soil-only or control conditions(NT). The experiment consisted of 17 treatments with four replications. Each pot contained 150 g soil and 1.125 g straw, had a moisture content of 80% of the field capacity, and was incubated for 53 days at 25°C. The rates of CO2-C emission, cumulative CO2-C evolution, total CO2 production in the soils of different treatments were measured to infer decomposition rates. The total organic carbon(TOC), labile organic carbon(LOC), and soil microbial biomass in the soils of different treatments were measured to infer soil quality. All results were significantly different(P<0.05) with the exception of the labile organic carbon(LOC). The maize and wheat straw showed different patterns in CO2 evolution rates. For both straw types, Zn had a synergic effect with U, but an antagonistic effect with the other N sources as determined by the total CO2 produced. The MUZ treatment showed the highest decomposition rate and cumulative CO2 concentration(1 120.29 mg/pot), whereas the WACZ treatment had the lowest cumulative CO2 concentration(1 040.57 mg/pot). The addition of NH4 Cl resulted in the highest total organic carbon(TOC) concentration(11.59 mg kg-1). The incorporation of wheat straw resulted in higher microbial biomass accumulation in soils relative to that of the maize straw application. The results demonstrate that mineral N sources can affect the ability of microorganisms to decompose straw, as well as the soil carbon concentrations.
文摘化石能源的过度消耗使开发新能源成为当务之急,燃料电池被认为是一种极具发展前景的高效能源转换装置.氧还原反应(ORR)和氧析出反应(OER)是燃料电池中至关重要的可逆氧电催化反应.由于氧反应的动力学迟缓,通常需要使用贵金属Pt和IrO_(2)分别催化ORR和OER反应.但其储量有限、价格高,因此,亟待开发廉价高效的氧反应催化剂.Co_(9)S_(8)属于镍黄铁矿晶型,由于其具有特殊的d带结构,被认为是一种多功能的电催化剂.Co_(9)S_(8)具有Oh构型的八面体位点和扭曲的C3v四面体位点,S的配位场效应诱导Co_(9)S_(8)中八面体Co的未成对电子在较低的费米能级上分裂成t2g和eg能带.基于d带理论,d带中心向费米能级的靠近有利于反键轨道的填充和更强的键合,为进一步优化Co_(9)S_(8)的电子结构提供了思路.本文以间苯二酚、甲醛和正硅酸四乙酯进行液相自发成核反应,由于SiO_(2)球和酚醛树脂的聚合速率不同形成了RF@SiO_(2)封装结构.经过高温碳化和碱蚀刻后,酚醛树脂外壳发生碳化并塌陷,形成了碗状的氮掺杂空心碳球(NHCS).然后将铁原子引入到Co_(9)S_(8)中并锚定在空心碳球上,制备了不同铁含量的Fe_(x)Co_(9‒x)S_(8)-NHCS复合催化剂.铁既可以占据钴镍黄铁矿结构中的八面体位,也可以占据四面体位.表征结果表明,当铁钴的比例不超过1:8时,低自旋的Fe^(2+)首先占据八面体位点;当铁钴的比例超过1:8时,四面体位的Co也可以被高自旋的Fe^(2+)取代.XPS结果表明,在引入Fe^(2+)后,Fe_(x)Co_(9‒x)S_(8)-NHCS中的Co^(2+)峰和Co0峰位置都产生了明显的偏移,表明Fe^(2+)在八面体位的占位会影响到四面体位的Co原子,进而有可能影响到电化学性能.结合Fe_(x)Co_(9‒x)S_(8)-NHCS的ORR和OER性能测试结果和结构表征数据可以看出,当Fe原子的系数x由0增至1,此时Fe^(2+)发生八面体位取代,金属‒硫键的键长也相应增加,从而提高了电催化活性.当x由1增加到4.5,此时Fe^(2+)发生四面体位取代,电催化活性降低.因此,铁钴的比例为1:8的复合催化剂在0.1 mol/L KOH中表现出了较好的ORR(E1/2=0.80 V vs.RHE)和OER(Ej=10=1.53 V vs.RHE)双功能电催化性能.最后,将最优比的铁钴(铁钴的比例为1:8)复合催化剂应用于碱性的可充电锌空气电池和中性环境的微生物燃料电池.具有复合催化剂阴极的锌空气电池和微生物燃料电池都表现出高功率密度和较好的稳定性,证实本文所开发的催化剂具有较好的应用价值.综上,本文不仅提出了一种合成高效催化剂的新策略,也还为促进钴镍黄铁矿结构氧催化剂的发展提供了重要的启示.
文摘Tomato is a common food on the human table. Up to now, the research on the growth and development model of tomato has been about 50 years. There are many researches on the main nutrients of tomato, such as carbon and nitrogen, but few on the trace element zinc. In this paper, taking plant nutrient C, N and Z<sub>n</sub> as variables, the differential equation model of C, N and Z<sub>n</sub> in tomato growth and development was established. According to the research of tomato as a whole and divided into root and leaf, the one-compartment and two-compartment models of tomato growth and development were established. The model was analyzed by Matlab program, and the existing experimental data was used to test the numerical simulation results, which proves that the model conforms to the facts.
