Nitrogen fixation is one of the most important sources of new nitrogen in the ocean and thus profoundly affects the nitrogen and carbon biogeochemical processes.The distribution,controlling factors,and flux of N2 fixa...Nitrogen fixation is one of the most important sources of new nitrogen in the ocean and thus profoundly affects the nitrogen and carbon biogeochemical processes.The distribution,controlling factors,and flux of N2 fixation in the global ocean remain uncertain,partly because of the lack of methodological uniformity.The^(15)N_(2)tracer assay(the original bubble method→the^(15)N_(2)-enriched seawater method→the modified bubble method)is the mainstream method for field measurements of N2 fixation rates(NFRs),among which the original bubble method is the most frequently used.However,accumulating evidence has suggested an underestimation of NFRs when using this method.To improve the availability of previous data,we compared NFRs measured by three^(15)N_(2)tracer assays in the South China Sea.Our results indicate that the relationship between NFRs measured by the original bubble method and the^(15)N_(2)-enriched seawater method varies obviously with area and season,which may be influenced by incubation time,diazotrophic composition,and environmental factors.In comparison,the relationship between NFRs measured by the original bubble method and the modified bubble method is more stable,indicating that the N2 fixation rates based on the original bubble methods may be underestimated by approximately 50%.Based on this result,we revised the flux of N2 fixation in the South China Sea to 40 mmol/(m2·a).Our results improve the availability and comparability of literature NFR data in the South China Sea.The comparison of the^(15)N_(2)tracer assay for NFRs measurements on a larger scale is urgently necessary over the global ocean for a more robust understanding of the role of N2 fixation in the marine nitrogen cycle.展开更多
The fabrication of heterojunction catalysts is an effective strategy to enhance charge separation efficiency,thus boosting the performance of photocatalysts.This work presents the synthesis and investigation of a nove...The fabrication of heterojunction catalysts is an effective strategy to enhance charge separation efficiency,thus boosting the performance of photocatalysts.This work presents the synthesis and investigation of a novel KNbO_(3)/Bi_(4)O_(5)Br_(2) heterostructure catalyst for photocatalytic N_(2)-to-NH_(3) conversion under light illumination.While morphology analysis revealed KNbO_(3) microcubes embedded within Bi_(4)O_(5)Br_(2) nanosheets,the composite exhibited no significant improvement in specific surface area or optical property compared to Bi_(4)O_(5)Br_(2) due to the relatively wide band gap and low surface area of KNbO_(3).The main contribution lies in the enhanced separation efficiency of photogenerated electrons and holes.Besides,the band structure analysis suggests that KNbO_(3) and Bi_(4)O_(5)Br_(2) exhibit suitable band potentials to form a type II heterojunction.Benefiting from the higher Fermi level of KNbO_(3) than Bi_(4)O_(5)Br_(2),the electron drift at the contact region thus occurs and leads to the formation of a built-in electric field with the direction from KNbO_(3) to Bi_(4)O_(5)Br_(2),accelerating electron migration and improving the operational efficiency of the photocatalysts.Consequently,the KNbO_(3)/Bi_(4)O_(5)Br_(2) catalyst shows an increased photoactivity,achieving an NH_(3) generation rate 1.78 and 1.58 times those of KNbO_(3) and Bi_(4)O_(5)Br_(2),respectively.This work may offer valuable insights for the design and synthesis of heterojunction composite photocatalysts.展开更多
Pot experimeats were carried out to estimate N2 fixation by vetch, milk vetch, sickle alfalfa and broadbean in pure stand using a 15N-labelled soil. Winter wheat was used as the non-fixing control. The 15N-labelled so...Pot experimeats were carried out to estimate N2 fixation by vetch, milk vetch, sickle alfalfa and broadbean in pure stand using a 15N-labelled soil. Winter wheat was used as the non-fixing control. The 15N-labelled soil used was prepared by growing corn-wheat-corn successively on a nearly organic-matter-free Xiashu loess supplemented with adequate amounts of (15NH4)aSO4, P, K and micronutrients, then incorporating these 15N-labelled plant msterials into the soil after each harvest, and allowing the plant materials to be decomposed aerobically for 410 d after incorporation of the plant material of the third crop. The 15N enrichment of wheat plant-N varied slightly with organs,with a maximum difference of 9.8%. Based on 15N enrichment of soil N inferred from the mean value of the 15N enrichment in different organs of wheat 79%-91% of total N in the tops and 67%-74% of total N in the roots of legumes studied were derived from atmosphere. Estimate by isotope dilution method was in good agreement with that by the conventional difference method provided values obtained by the latter were corrected for seed N, and also with that from the measurement of N accumulated in the tops of the legumes.展开更多
In this paper,Cu-doped Bi_(2)WO_(6)was synthesized via a solvothermal method and applied it in photocatalytic N_(2)immobilization.Characterization results showed the presence of a small amount of metallic Bi in the ph...In this paper,Cu-doped Bi_(2)WO_(6)was synthesized via a solvothermal method and applied it in photocatalytic N_(2)immobilization.Characterization results showed the presence of a small amount of metallic Bi in the photocatalyst,indicating that the synthesized photocatalyst is actually Bi/Cu-Bi_(2)WO_(6)composite.The doped Cu had a valence state of+2 and most likely substituted the position of Bi^(3+).The introduced Cu did not affect the metallic Bi content,but mainly influenced the energy band structure of Bi_(2)WO_(6).The band gap was slightly narrowed,the conduction band was elevated,and the work function was reduced.The reduced work function improved the transfer and separation of charge carriers,which mainly caused the increased photoactivity.The optimized NH_(3)generation rates of Bi/Cu-Bi_(2)WO_(6)reached 624 and 243μmol·L^(-1)·g^(-1)·h^(-1)under simulated solar and visible light,and these values were approximately 2.8 and 5.9 times higher those of Bi/Bi_(2)WO_(6),respectively.This research provides a method for improving the photocatalytic N_(2)fixation and may provide more information on the design and preparation of heteroatom-doped semiconductor photocatalysts for N_(2)-to-NH_(3)conversion.展开更多
Urea is widely used as fertilizer and is a key substance supporting global food production. However, the traditional industrial synthesis of urea faces the challenges with high energy consumption and serious environme...Urea is widely used as fertilizer and is a key substance supporting global food production. However, the traditional industrial synthesis of urea faces the challenges with high energy consumption and serious environmental problems. With the increasing global demand for environmental protection and sustainable development, it is much necessary to develop novel and clean methods for the synthesis of urea.Electrocatalysis provides an efficient and renewable synthesis route that can directly produce urea at room temperature and atmospheric pressure by the coupling of CO_(2) and nitrogenous molecules. In this review, we summarized the most recent advances in electrochemical synthesis of urea via CAN coupling systematically, focusing on the coupling of CO_(2) and different nitrogen sources. And the associated coupling mechanism, catalysts optimization, and electrolyzer design are well discussed. Moreover, the challenges and future directions for electrocatalytic CAN coupling are prospected. This review will provide timely and valuable guidance for others and attract more interests to promote the development of electrochemical synthesis of urea or other valuable chemicals containing CAN bond.展开更多
Nowadays catalytic nitrogen reduction reaction(NRR)by electrochemistry has attracted much attention because of its key role in producing the basic chemical product ammonia with low energy consumption.A stable and envi...Nowadays catalytic nitrogen reduction reaction(NRR)by electrochemistry has attracted much attention because of its key role in producing the basic chemical product ammonia with low energy consumption.A stable and environmentally‐friendly single‐or multi‐atom catalyst with good performance in activity and selectivity is highly desired for NRR.From density functional theory calculations,the NRR mechanisms catalyzed by Nb monomer,dimer,trimer and tetramer anchored on graphitic carbon nitride(Nb_(x)@g‐C_(3)N_(4),x=1,2,3,4)have been deeply explored.It has been found that Nb_(3)@g‐C_(3)N_(4) exhibits the best catalytic ability among the four catalysts with the introduction of H+.A more stable intermediate(*NH_(2)+*H)can be found to reduce the huge free energy barrier of forming*NH_(3) from*NH_(2) directly in a multi‐atom system.By analyzing the density of states and projected crystal orbital Hamilton population,a synergistic effect among Nb atoms and the adsorbed H^(+)is responsible for reducing the overpotential of NRR.Furthermore,the competitive hydrogen evolution reaction is suppressed effectively.This work introduces a new insight in the reaction pathway in multi‐atoms for developing high‐efficiency NRR catalysts.展开更多
As a fascinating alternative to the energy-intensive Haber-Bosch process,the electrochemically-driven N_(2) reduction reaction(NRR)utilizing the N_(2) and H_(2)O for the production of NH3 has received enormous attenti...As a fascinating alternative to the energy-intensive Haber-Bosch process,the electrochemically-driven N_(2) reduction reaction(NRR)utilizing the N_(2) and H_(2)O for the production of NH3 has received enormous attention.The development and preparation of promising electrocatalysts are requisite to realize an efficient N_(2) conversion for NH3 production.In this research,we propose a template-assisted strategy to construct the hollow electrocatalyst with controllable morphology.As a paradigm,the hollow Cr_(2)O_(3) nanocatalyst with a uniform size(~170 nm),small cavity and ultrathin shell(~15 nm)is successfully fabricated with this strategy.This promising hollow structure is favourable to trap N_(2) into the cavity,provides abundant active sites to accelerate the three-phase interactions,and facilitates the reactant transfer across the shell.Attributed to these synergetic effects,the designed catalyst displays an outstanding behaviour in N_(2) fixation for NH3 production in ambient condition.In the neutral electrolyte of 0.1 mol·L^(-1) Na_(2)SO_(4),an impressive electrocatalytic performance with the NH3 generation rate of 2.72μg·h^(-1)·cm^(-2) and a high FE of 5.31%is acquired respectively at-0.85 V with the hollow Cr_(2)O_(3) catalyst.Inspired by this work,it is highly expected that this approach could be applied as a universal strategy and extended to fabricating other promising electrocatalysts for realizing highly efficient nitrogen reduction reaction(NRR).展开更多
Recently,widespread attention has been devoted to the typical layered BiOCl or BiOBr because of the suitable nanostructure and band structure.However,owing to the fast carrier recombination,the photocatalytic performa...Recently,widespread attention has been devoted to the typical layered BiOCl or BiOBr because of the suitable nanostructure and band structure.However,owing to the fast carrier recombination,the photocatalytic performance of BiOX materials is not so satisfactory.Loading 1T phase WS_(2)nanosheets(NSs)onto Bi_(5)O_(7)Br NSs can improve the photocatalytic N_(2)fixation activity.Among these,the obtained 1T-WS_(2)@Bi_(5)O_(7)Br composites with optimum 5%1T-WS_(2)NSs display a significantly improved photocatalytic N_(2)fixation rate(8.43 mmol L^(−1)h^(−1)g^(−1)),2.51 times higher than pure Bi_(5)O_(7)Br(3.36 mmol L^(−1)h^(−1)g^(−1)).And the outstanding stability of 1T-WS_(2)@Bi_(5)O_(7)Br-5 composites is also achieved.Exactly,the photoexcited electrons from Bi_(5)O_(7)Br NSs are quickly transferred to conductive 1T phase WS_(2)as electron acceptors,which can promote the separation of carriers.In addition,1T-WS_(2)NSs can provide abundant active sites on the basal and edge planes,which can promote the efficiency of photocatalytic N_(2)fixation.This work offers a novel solution to improve the photocatalytic performance of Bi_(5)O_(7)Br NSs.展开更多
基金The National Natural Science Foundation of China under contract Nos 42076042 and 41721005the Fund of Ministry of Science and Technology of China under contract No.2017FY201403the Fund of China Ocean Mineral Resources R&D Association under contract No.DY135-13-E2-03.
文摘Nitrogen fixation is one of the most important sources of new nitrogen in the ocean and thus profoundly affects the nitrogen and carbon biogeochemical processes.The distribution,controlling factors,and flux of N2 fixation in the global ocean remain uncertain,partly because of the lack of methodological uniformity.The^(15)N_(2)tracer assay(the original bubble method→the^(15)N_(2)-enriched seawater method→the modified bubble method)is the mainstream method for field measurements of N2 fixation rates(NFRs),among which the original bubble method is the most frequently used.However,accumulating evidence has suggested an underestimation of NFRs when using this method.To improve the availability of previous data,we compared NFRs measured by three^(15)N_(2)tracer assays in the South China Sea.Our results indicate that the relationship between NFRs measured by the original bubble method and the^(15)N_(2)-enriched seawater method varies obviously with area and season,which may be influenced by incubation time,diazotrophic composition,and environmental factors.In comparison,the relationship between NFRs measured by the original bubble method and the modified bubble method is more stable,indicating that the N2 fixation rates based on the original bubble methods may be underestimated by approximately 50%.Based on this result,we revised the flux of N2 fixation in the South China Sea to 40 mmol/(m2·a).Our results improve the availability and comparability of literature NFR data in the South China Sea.The comparison of the^(15)N_(2)tracer assay for NFRs measurements on a larger scale is urgently necessary over the global ocean for a more robust understanding of the role of N2 fixation in the marine nitrogen cycle.
基金supported by the National Natural Science Foundation of China (Grant No.22172144)the Key Research and Development Program of Zhejiang Province (Grant No.2023C03148).
文摘The fabrication of heterojunction catalysts is an effective strategy to enhance charge separation efficiency,thus boosting the performance of photocatalysts.This work presents the synthesis and investigation of a novel KNbO_(3)/Bi_(4)O_(5)Br_(2) heterostructure catalyst for photocatalytic N_(2)-to-NH_(3) conversion under light illumination.While morphology analysis revealed KNbO_(3) microcubes embedded within Bi_(4)O_(5)Br_(2) nanosheets,the composite exhibited no significant improvement in specific surface area or optical property compared to Bi_(4)O_(5)Br_(2) due to the relatively wide band gap and low surface area of KNbO_(3).The main contribution lies in the enhanced separation efficiency of photogenerated electrons and holes.Besides,the band structure analysis suggests that KNbO_(3) and Bi_(4)O_(5)Br_(2) exhibit suitable band potentials to form a type II heterojunction.Benefiting from the higher Fermi level of KNbO_(3) than Bi_(4)O_(5)Br_(2),the electron drift at the contact region thus occurs and leads to the formation of a built-in electric field with the direction from KNbO_(3) to Bi_(4)O_(5)Br_(2),accelerating electron migration and improving the operational efficiency of the photocatalysts.Consequently,the KNbO_(3)/Bi_(4)O_(5)Br_(2) catalyst shows an increased photoactivity,achieving an NH_(3) generation rate 1.78 and 1.58 times those of KNbO_(3) and Bi_(4)O_(5)Br_(2),respectively.This work may offer valuable insights for the design and synthesis of heterojunction composite photocatalysts.
文摘Pot experimeats were carried out to estimate N2 fixation by vetch, milk vetch, sickle alfalfa and broadbean in pure stand using a 15N-labelled soil. Winter wheat was used as the non-fixing control. The 15N-labelled soil used was prepared by growing corn-wheat-corn successively on a nearly organic-matter-free Xiashu loess supplemented with adequate amounts of (15NH4)aSO4, P, K and micronutrients, then incorporating these 15N-labelled plant msterials into the soil after each harvest, and allowing the plant materials to be decomposed aerobically for 410 d after incorporation of the plant material of the third crop. The 15N enrichment of wheat plant-N varied slightly with organs,with a maximum difference of 9.8%. Based on 15N enrichment of soil N inferred from the mean value of the 15N enrichment in different organs of wheat 79%-91% of total N in the tops and 67%-74% of total N in the roots of legumes studied were derived from atmosphere. Estimate by isotope dilution method was in good agreement with that by the conventional difference method provided values obtained by the latter were corrected for seed N, and also with that from the measurement of N accumulated in the tops of the legumes.
基金The work was financially supported by National Natural Science Foundation of China(Grant No.22172144)Natural Science Foundation of Zhejiang Province(Grant No.LY20B030004).
文摘In this paper,Cu-doped Bi_(2)WO_(6)was synthesized via a solvothermal method and applied it in photocatalytic N_(2)immobilization.Characterization results showed the presence of a small amount of metallic Bi in the photocatalyst,indicating that the synthesized photocatalyst is actually Bi/Cu-Bi_(2)WO_(6)composite.The doped Cu had a valence state of+2 and most likely substituted the position of Bi^(3+).The introduced Cu did not affect the metallic Bi content,but mainly influenced the energy band structure of Bi_(2)WO_(6).The band gap was slightly narrowed,the conduction band was elevated,and the work function was reduced.The reduced work function improved the transfer and separation of charge carriers,which mainly caused the increased photoactivity.The optimized NH_(3)generation rates of Bi/Cu-Bi_(2)WO_(6)reached 624 and 243μmol·L^(-1)·g^(-1)·h^(-1)under simulated solar and visible light,and these values were approximately 2.8 and 5.9 times higher those of Bi/Bi_(2)WO_(6),respectively.This research provides a method for improving the photocatalytic N_(2)fixation and may provide more information on the design and preparation of heteroatom-doped semiconductor photocatalysts for N_(2)-to-NH_(3)conversion.
基金National Natural Science Foundation of China (No. 22202065, 22075092 and U21A20500)。
文摘Urea is widely used as fertilizer and is a key substance supporting global food production. However, the traditional industrial synthesis of urea faces the challenges with high energy consumption and serious environmental problems. With the increasing global demand for environmental protection and sustainable development, it is much necessary to develop novel and clean methods for the synthesis of urea.Electrocatalysis provides an efficient and renewable synthesis route that can directly produce urea at room temperature and atmospheric pressure by the coupling of CO_(2) and nitrogenous molecules. In this review, we summarized the most recent advances in electrochemical synthesis of urea via CAN coupling systematically, focusing on the coupling of CO_(2) and different nitrogen sources. And the associated coupling mechanism, catalysts optimization, and electrolyzer design are well discussed. Moreover, the challenges and future directions for electrocatalytic CAN coupling are prospected. This review will provide timely and valuable guidance for others and attract more interests to promote the development of electrochemical synthesis of urea or other valuable chemicals containing CAN bond.
文摘Nowadays catalytic nitrogen reduction reaction(NRR)by electrochemistry has attracted much attention because of its key role in producing the basic chemical product ammonia with low energy consumption.A stable and environmentally‐friendly single‐or multi‐atom catalyst with good performance in activity and selectivity is highly desired for NRR.From density functional theory calculations,the NRR mechanisms catalyzed by Nb monomer,dimer,trimer and tetramer anchored on graphitic carbon nitride(Nb_(x)@g‐C_(3)N_(4),x=1,2,3,4)have been deeply explored.It has been found that Nb_(3)@g‐C_(3)N_(4) exhibits the best catalytic ability among the four catalysts with the introduction of H+.A more stable intermediate(*NH_(2)+*H)can be found to reduce the huge free energy barrier of forming*NH_(3) from*NH_(2) directly in a multi‐atom system.By analyzing the density of states and projected crystal orbital Hamilton population,a synergistic effect among Nb atoms and the adsorbed H^(+)is responsible for reducing the overpotential of NRR.Furthermore,the competitive hydrogen evolution reaction is suppressed effectively.This work introduces a new insight in the reaction pathway in multi‐atoms for developing high‐efficiency NRR catalysts.
基金supported by Australian Research Council Discovery Projects(DP170104264 and DP190103548)。
文摘As a fascinating alternative to the energy-intensive Haber-Bosch process,the electrochemically-driven N_(2) reduction reaction(NRR)utilizing the N_(2) and H_(2)O for the production of NH3 has received enormous attention.The development and preparation of promising electrocatalysts are requisite to realize an efficient N_(2) conversion for NH3 production.In this research,we propose a template-assisted strategy to construct the hollow electrocatalyst with controllable morphology.As a paradigm,the hollow Cr_(2)O_(3) nanocatalyst with a uniform size(~170 nm),small cavity and ultrathin shell(~15 nm)is successfully fabricated with this strategy.This promising hollow structure is favourable to trap N_(2) into the cavity,provides abundant active sites to accelerate the three-phase interactions,and facilitates the reactant transfer across the shell.Attributed to these synergetic effects,the designed catalyst displays an outstanding behaviour in N_(2) fixation for NH3 production in ambient condition.In the neutral electrolyte of 0.1 mol·L^(-1) Na_(2)SO_(4),an impressive electrocatalytic performance with the NH3 generation rate of 2.72μg·h^(-1)·cm^(-2) and a high FE of 5.31%is acquired respectively at-0.85 V with the hollow Cr_(2)O_(3) catalyst.Inspired by this work,it is highly expected that this approach could be applied as a universal strategy and extended to fabricating other promising electrocatalysts for realizing highly efficient nitrogen reduction reaction(NRR).
基金funding from the National Natural Science Foundation of China(Nos.51872173 and 51772176)Taishan Scholars Program of Shandong Province(No.tsqn201812068)+1 种基金Higher School Youth Innovation Team of Shandong Province(No.2019KJA013)Science and Technology Special Project of Qingdao City(No.20-3-4-3-nsh).
文摘Recently,widespread attention has been devoted to the typical layered BiOCl or BiOBr because of the suitable nanostructure and band structure.However,owing to the fast carrier recombination,the photocatalytic performance of BiOX materials is not so satisfactory.Loading 1T phase WS_(2)nanosheets(NSs)onto Bi_(5)O_(7)Br NSs can improve the photocatalytic N_(2)fixation activity.Among these,the obtained 1T-WS_(2)@Bi_(5)O_(7)Br composites with optimum 5%1T-WS_(2)NSs display a significantly improved photocatalytic N_(2)fixation rate(8.43 mmol L^(−1)h^(−1)g^(−1)),2.51 times higher than pure Bi_(5)O_(7)Br(3.36 mmol L^(−1)h^(−1)g^(−1)).And the outstanding stability of 1T-WS_(2)@Bi_(5)O_(7)Br-5 composites is also achieved.Exactly,the photoexcited electrons from Bi_(5)O_(7)Br NSs are quickly transferred to conductive 1T phase WS_(2)as electron acceptors,which can promote the separation of carriers.In addition,1T-WS_(2)NSs can provide abundant active sites on the basal and edge planes,which can promote the efficiency of photocatalytic N_(2)fixation.This work offers a novel solution to improve the photocatalytic performance of Bi_(5)O_(7)Br NSs.
