The ammonia synthesis from nitrogen and water under ambient conditions is one of the most inviting but challenging reaction routes.Although nitrogen is abundant in the atmosphere and the ammonia synthesis reaction is ...The ammonia synthesis from nitrogen and water under ambient conditions is one of the most inviting but challenging reaction routes.Although nitrogen is abundant in the atmosphere and the ammonia synthesis reaction is exothermic on the thermodynamics,the conversion of N2 to ammonia is actually hard to proceed owing to the chemical inertness and stability of N2 molecules.In industry,ammonia synthesis is carried out by the Haber-Bosch process under harsh conditions (300-500 ℃,20-30 MPa) associated with the requirement of substantial energy input and the enormous emission of greenhouse gases (e.g.,CO2).Recently,a growing number of studies on photo(electro)catalytic and electrocatalytic nitrogen reduction reaction (NRR) in aqueous solution have attracted extensive attention,which holds great promise for nitrogen fixation under room temperature and atmospheric pressure.However,the very low efficiency and ambiguous mechanism still remain as the major hurdles for the development of photochemical and electrochemical NRR systems.Here we provide an overview of the latest progresses,remaining challenges and future prospects in photocatalytic and electrocatalytic nitrogen fixation.Moreover,this review offers a helpful guidance for the reasonable design of photocatalysts and electrocatalysts towards NRR by combining theory predictions and experiment results.We hope this review can stimulate more research interests in the relatively understudied but highly promising research field of NRR.展开更多
采用Zigzag型煤焦表面模型,利用量子化学密度泛函理论研究了煤焦异相还原N_2O的反应机理。首先分析了Zigzag和Armchair碳基模型的差异本质,然后通过热力学分析和动力学分析研究了煤焦异相还原N_2O的反应机理,最后对比分析了Zigzag和Armc...采用Zigzag型煤焦表面模型,利用量子化学密度泛函理论研究了煤焦异相还原N_2O的反应机理。首先分析了Zigzag和Armchair碳基模型的差异本质,然后通过热力学分析和动力学分析研究了煤焦异相还原N_2O的反应机理,最后对比分析了Zigzag和Armchair两模型计算结果。研究表明,煤焦异相还原N_2O的反应包括吸附、还原及脱附3个过程,N2的脱附过程是整个反应的决速步。煤焦异相还原N_2O的反应在循环流化床炉温范围内是可自发的放热反应,反应平衡常数大于105,可认为是单向反应。根据决速步理论,Zigzag模型下的反应活化能为66.28 k J/mol,阿累尼乌斯表达式为1.07×1014exp(-7 972.4/T),Armchair模型下的反应活化能为160.99 k J/mol,阿累尼乌斯表达式为3.99×1015exp(-19 364.0/T)。Zigzag模型下的还原反应活化能小,反应速率常数大,反应更为活跃。两模型计算差异主要是由于Zigzag模型存在未成对电子,化学性质活跃导致的。在涉及碳基反应的理论计算时,应充分考虑计算模型对反应过程研究的影响。展开更多
The Cu2O/SiC photocatalyst was obtained from SiC nanoparticles （NPs） modified by Cu2O. Their photocatalytic activities for reducing CO2 to CH3OH under visible light irradiation have been investigated. The results in...The Cu2O/SiC photocatalyst was obtained from SiC nanoparticles （NPs） modified by Cu2O. Their photocatalytic activities for reducing CO2 to CH3OH under visible light irradiation have been investigated. The results indicated that besides a small quantity of 6H-SiC, SiC NPs mainly consisted of 3C-SiC. The band gaps of SiC and Cu2O were estimated to be about 1.95 and 2.23 eV from UV-Vis spectra, respectively. The Cu2O modification can enhance the photocatalytic performance of SiC NPs, and the largest yields of methanol on SiC, Cu2O and Cu2O/SiC photocatalysts under visible light irradiation were 153, 104 and 191μmol/g, respectively.展开更多
Substantial NO_(x) emission mitigation is crucial for the synergistic reduction of particulate matter and ozone(O_(3))pollution in China.The traditional air quality model does not consider heterogeneous HONO chemistry...Substantial NO_(x) emission mitigation is crucial for the synergistic reduction of particulate matter and ozone(O_(3))pollution in China.The traditional air quality model does not consider heterogeneous HONO chemistry,leading to uncertainties in estimating the benefits of NO_(x) control.Previous studies have shown that the parameterization of heterogeneous HONO formation increases both the simulated value of sulfate–nitrate–ammonium(SNA)and that of O_(3),thus adding the heterogeneous reactions of HONO into air quality models inevitably leads to changes in the estimated benefits of NO_(x) abatement.Here we investigated the changes in SNA and O_(3)concentrations from NO_(x) emission reduction before and after adding heterogeneous HONO reactions in the Community Multi-Scale Air Quality(CMAQ)model.Including heterogeneous HONO reactions in the simulation improved the benefits of NO_(x) reduction in terms of SNA control in winter.With 80%NO_(x) reduction,the reduction in SNA increased from 36.9%without considering heterogeneous HONO reactions to 42.8%with heterogeneous HONO chemistry.The reduction in the maximum daily 8h average(MDA8)O_(3)in summer caused by NO_(x) reduction increased slightly from 4.7%to 5.2%after adding heterogeneous HONO reactions.The results in this study highlight the enhanced effectiveness of NO_(x) controls for the reduction of SNA and O_(3)after considering heterogeneous HONO formation in a complex chemical ambient,demonstrating the importance of NO_(x) controls in reducing PM2.5 and O_(3)pollution in China.展开更多
Electrochemical advanced oxidation processes (EAOPs) are effective and environmentally friendly for the treatment of refractory organic pollutants.Among EAOPs,heterogeneous electro-Fenton (EF) process with in-situ for...Electrochemical advanced oxidation processes (EAOPs) are effective and environmentally friendly for the treatment of refractory organic pollutants.Among EAOPs,heterogeneous electro-Fenton (EF) process with in-situ formation of hydrogen peroxide (H_(2)O_(2)) is an eco-friendly,cost-effective and easy-operable technology to generate hydroxyl radicals (;OH) with high redox potential.The generation of;OH is determined by the synergistic H_(2)O_(2)formation and activation.The surface catalytic mechanisms for H_(2)O_(2)activation in the heterogeneous EF process were discussed.Some required features such as heteroatom doping and oxygen groups for H_(2)O_(2)formation via selective two-electron oxygen reduction reaction (ORR) with carbonaceous electrode are summarized.The solid Fenton catalysts and integrated functional cathodes that widely used in heterogeneous EF for wastewater treatment are grouped into few classes.And the brief discussion on catalytic activity and stability of materials over different experimental conditions are given.In addition,the application of heterogeneous EF process on the remediation of emerging contaminants is provided.The challenges and future prospects of the heterogeneous EF processes about catalytic fall-off and multi-step/complex techniques for water purification are emphasized.展开更多
Nitrate from the application of nitrogen-based fertilizers in intensive agriculture is a notorious waste product, though it lacks cost-effective solutions for its removal from potential drinking water resources. Catal...Nitrate from the application of nitrogen-based fertilizers in intensive agriculture is a notorious waste product, though it lacks cost-effective solutions for its removal from potential drinking water resources. Catalytic reduction appears to be a promising technique for converting nitrates to benign nitrogen gas. Mesoporous silica SBA-15 is a frequently used catalyst support that has large surface areas and highly ordered nanopores. In this work, mesoporous silica SBA-15 bimetallic catalysts for nitrate reduction were investigated. The catalyst was optimized for the selection of promoter metal (Sn and Cu), noble metal (Pd and Pt) and loading ratios of these metals at different temperatures and reduction conditions. The catalysts prepared were characterized by FT-IR, N2 physisorption, XRD, SEM, and ICP. All catalysts showed the presence of cylindrical mesoporous channels and uniform pore structures that remained even after metals loading. In the presence of a CO<sub>2</sub> buffer, the catalysts 4Pd-1Cu/SBA-15 and 1Pt-1Cu/SBA-15 reduced at 100?C under H2 and 1Pd-1Cu/SBA-15 reduced at 200°C under H2 demonstrated very high nitrate conversion. Furthermore, the forementioned Pd catalysts had higher N2 selectivity (88% - 87%) compared to Pt catalyst (80%). Nitrate conversion by the 4Pd-1Cu/SBA-15 catalyst was significantly decreased to 81% in the absence of CO<sub>2</sub>.展开更多
In this study,a CFD model coupled with heterogeneous flow structure,mass transfer equations,and chemical reaction kinetics is established to forecast the pyrolusite reduction reaction behavior.Compared with the previo...In this study,a CFD model coupled with heterogeneous flow structure,mass transfer equations,and chemical reaction kinetics is established to forecast the pyrolusite reduction reaction behavior.Compared with the previous studies which ignore the volume change of solids phase,the influence of volume shrinkage on reaction and flow behavior is explored in this research.Volume shrinkage of pyrolusite is proved to be non-negligible in predicting the conversion rate.The negligence of volume shrinkage leads to the overestimation of conversion rate for its inaccurate estimation of surface area for reaction.Besides,the influence of volume shrinkage on the reaction is found smaller in the scaled-up reactor.展开更多
基金the National Key R&D Program of China (Nos.2017YFA0208200,2016YFB0700600,and 2015CB659300)the National Natural Science Foundation of China (NSFC)(Nos. 21872069,51761135104,and 21573108)+2 种基金the Natural Science Foundation of Jiangsu Province (Nos.BK20180008 and BK20150571)High-Level Entrepreneurial and Innovative Talents Program of Jiangsu Provincethe Fundamental Research Funds for the Central Universities of China (No.020514380146).
文摘The ammonia synthesis from nitrogen and water under ambient conditions is one of the most inviting but challenging reaction routes.Although nitrogen is abundant in the atmosphere and the ammonia synthesis reaction is exothermic on the thermodynamics,the conversion of N2 to ammonia is actually hard to proceed owing to the chemical inertness and stability of N2 molecules.In industry,ammonia synthesis is carried out by the Haber-Bosch process under harsh conditions (300-500 ℃,20-30 MPa) associated with the requirement of substantial energy input and the enormous emission of greenhouse gases (e.g.,CO2).Recently,a growing number of studies on photo(electro)catalytic and electrocatalytic nitrogen reduction reaction (NRR) in aqueous solution have attracted extensive attention,which holds great promise for nitrogen fixation under room temperature and atmospheric pressure.However,the very low efficiency and ambiguous mechanism still remain as the major hurdles for the development of photochemical and electrochemical NRR systems.Here we provide an overview of the latest progresses,remaining challenges and future prospects in photocatalytic and electrocatalytic nitrogen fixation.Moreover,this review offers a helpful guidance for the reasonable design of photocatalysts and electrocatalysts towards NRR by combining theory predictions and experiment results.We hope this review can stimulate more research interests in the relatively understudied but highly promising research field of NRR.
文摘采用Zigzag型煤焦表面模型,利用量子化学密度泛函理论研究了煤焦异相还原N_2O的反应机理。首先分析了Zigzag和Armchair碳基模型的差异本质,然后通过热力学分析和动力学分析研究了煤焦异相还原N_2O的反应机理,最后对比分析了Zigzag和Armchair两模型计算结果。研究表明,煤焦异相还原N_2O的反应包括吸附、还原及脱附3个过程,N2的脱附过程是整个反应的决速步。煤焦异相还原N_2O的反应在循环流化床炉温范围内是可自发的放热反应,反应平衡常数大于105,可认为是单向反应。根据决速步理论,Zigzag模型下的反应活化能为66.28 k J/mol,阿累尼乌斯表达式为1.07×1014exp(-7 972.4/T),Armchair模型下的反应活化能为160.99 k J/mol,阿累尼乌斯表达式为3.99×1015exp(-19 364.0/T)。Zigzag模型下的还原反应活化能小,反应速率常数大,反应更为活跃。两模型计算差异主要是由于Zigzag模型存在未成对电子,化学性质活跃导致的。在涉及碳基反应的理论计算时,应充分考虑计算模型对反应过程研究的影响。
基金supported by the National Natural Science Foundation of China (Grant No. 20906034)the Key Academic Program of the 3rd Phase "211 Project" of South China Agricultural University (Grant No. 2009B010100001)China Postdoctoral Science Foundation (Grant No. 20080430820)
文摘The Cu2O/SiC photocatalyst was obtained from SiC nanoparticles （NPs） modified by Cu2O. Their photocatalytic activities for reducing CO2 to CH3OH under visible light irradiation have been investigated. The results indicated that besides a small quantity of 6H-SiC, SiC NPs mainly consisted of 3C-SiC. The band gaps of SiC and Cu2O were estimated to be about 1.95 and 2.23 eV from UV-Vis spectra, respectively. The Cu2O modification can enhance the photocatalytic performance of SiC NPs, and the largest yields of methanol on SiC, Cu2O and Cu2O/SiC photocatalysts under visible light irradiation were 153, 104 and 191μmol/g, respectively.
基金supported by the Innovation Platform for Academicians of Hainan Province(No.YSPTZX202205)the National Key Research and Development Program of China(No.2022YFC3703404)+2 种基金the National Natural Science Foundation of China(No.22276205)the Excellent Young Talents Project of Yellow River Conservancy Commission(No.HQK-202313)the Research and Development Project of Yellow River Institute of Hydraulic Research(No.HKY-YF-2022-02)。
文摘Substantial NO_(x) emission mitigation is crucial for the synergistic reduction of particulate matter and ozone(O_(3))pollution in China.The traditional air quality model does not consider heterogeneous HONO chemistry,leading to uncertainties in estimating the benefits of NO_(x) control.Previous studies have shown that the parameterization of heterogeneous HONO formation increases both the simulated value of sulfate–nitrate–ammonium(SNA)and that of O_(3),thus adding the heterogeneous reactions of HONO into air quality models inevitably leads to changes in the estimated benefits of NO_(x) abatement.Here we investigated the changes in SNA and O_(3)concentrations from NO_(x) emission reduction before and after adding heterogeneous HONO reactions in the Community Multi-Scale Air Quality(CMAQ)model.Including heterogeneous HONO reactions in the simulation improved the benefits of NO_(x) reduction in terms of SNA control in winter.With 80%NO_(x) reduction,the reduction in SNA increased from 36.9%without considering heterogeneous HONO reactions to 42.8%with heterogeneous HONO chemistry.The reduction in the maximum daily 8h average(MDA8)O_(3)in summer caused by NO_(x) reduction increased slightly from 4.7%to 5.2%after adding heterogeneous HONO reactions.The results in this study highlight the enhanced effectiveness of NO_(x) controls for the reduction of SNA and O_(3)after considering heterogeneous HONO formation in a complex chemical ambient,demonstrating the importance of NO_(x) controls in reducing PM2.5 and O_(3)pollution in China.
基金funding from the National Natural Science Foundation of China (Nos.22076142,21677106,22076140)National Key Basic Research Program of China (No.2017YFA0403402)+2 种基金National Natural Science Foundation of China (No.U1932119)the Science & Technology Commission of Shanghai Municipality (No.14DZ2261100)the Fundamental Research Funds for the Central Universities。
文摘Electrochemical advanced oxidation processes (EAOPs) are effective and environmentally friendly for the treatment of refractory organic pollutants.Among EAOPs,heterogeneous electro-Fenton (EF) process with in-situ formation of hydrogen peroxide (H_(2)O_(2)) is an eco-friendly,cost-effective and easy-operable technology to generate hydroxyl radicals (;OH) with high redox potential.The generation of;OH is determined by the synergistic H_(2)O_(2)formation and activation.The surface catalytic mechanisms for H_(2)O_(2)activation in the heterogeneous EF process were discussed.Some required features such as heteroatom doping and oxygen groups for H_(2)O_(2)formation via selective two-electron oxygen reduction reaction (ORR) with carbonaceous electrode are summarized.The solid Fenton catalysts and integrated functional cathodes that widely used in heterogeneous EF for wastewater treatment are grouped into few classes.And the brief discussion on catalytic activity and stability of materials over different experimental conditions are given.In addition,the application of heterogeneous EF process on the remediation of emerging contaminants is provided.The challenges and future prospects of the heterogeneous EF processes about catalytic fall-off and multi-step/complex techniques for water purification are emphasized.
文摘Nitrate from the application of nitrogen-based fertilizers in intensive agriculture is a notorious waste product, though it lacks cost-effective solutions for its removal from potential drinking water resources. Catalytic reduction appears to be a promising technique for converting nitrates to benign nitrogen gas. Mesoporous silica SBA-15 is a frequently used catalyst support that has large surface areas and highly ordered nanopores. In this work, mesoporous silica SBA-15 bimetallic catalysts for nitrate reduction were investigated. The catalyst was optimized for the selection of promoter metal (Sn and Cu), noble metal (Pd and Pt) and loading ratios of these metals at different temperatures and reduction conditions. The catalysts prepared were characterized by FT-IR, N2 physisorption, XRD, SEM, and ICP. All catalysts showed the presence of cylindrical mesoporous channels and uniform pore structures that remained even after metals loading. In the presence of a CO<sub>2</sub> buffer, the catalysts 4Pd-1Cu/SBA-15 and 1Pt-1Cu/SBA-15 reduced at 100?C under H2 and 1Pd-1Cu/SBA-15 reduced at 200°C under H2 demonstrated very high nitrate conversion. Furthermore, the forementioned Pd catalysts had higher N2 selectivity (88% - 87%) compared to Pt catalyst (80%). Nitrate conversion by the 4Pd-1Cu/SBA-15 catalyst was significantly decreased to 81% in the absence of CO<sub>2</sub>.
基金grateful to the National Natural Science Foundation of China(grant No.21878304 and 21736010)the Strategic Priority Research Program of the Chinese Academy of Sciences(grant No.XDA29040200)the Science Fund for Creative Research Groups of the National Natural Science Foundation of China(grant No.21921005).
文摘In this study,a CFD model coupled with heterogeneous flow structure,mass transfer equations,and chemical reaction kinetics is established to forecast the pyrolusite reduction reaction behavior.Compared with the previous studies which ignore the volume change of solids phase,the influence of volume shrinkage on reaction and flow behavior is explored in this research.Volume shrinkage of pyrolusite is proved to be non-negligible in predicting the conversion rate.The negligence of volume shrinkage leads to the overestimation of conversion rate for its inaccurate estimation of surface area for reaction.Besides,the influence of volume shrinkage on the reaction is found smaller in the scaled-up reactor.
