Formaldehyde(HCHO) is a common indoor pollutant, long-term exposure to HCHO may harm human health. Its efficient removal at mild conditions is still challenging. The catalytic oxidation of HCHO molecules on a single a...Formaldehyde(HCHO) is a common indoor pollutant, long-term exposure to HCHO may harm human health. Its efficient removal at mild conditions is still challenging. The catalytic oxidation of HCHO molecules on a single atomic catalyst, Ti-decorated Ti3C2O2(Ti/Ti3C2O2) monolayer, is investigated by performing the first principles calculations in this work. It demonstrates that Ti atoms can be easily well dispersed at the form of single atom on Ti3C2O2 monolayer without aggregation. For HCHO catalytic oxidation, both Langmuir-Hinshelwood(LH) and Eley-Rideal(ER) mechanisms are considered. The results show that the step of HCHO dissociative adsorption on Ti/Ti3C2O2 with activated O2 can release high energy of 4.05 e V based on the ER mechanism, which can help to overcome the energy barrier(1.04 e V) of the subsequent reaction steps. The charge transfer from *OH group to CO molecule(dissociated from HCHO) not only promotes *OH group activation but also plays an important role in the H2 O generation along the ER mechanism. Therefore, HCHO can be oxidized easily on Ti/Ti3C2O2 monolayer, this work could provide significant guidance to develop effective non-noble metal catalysts for HCHO oxidation and broaden the applications of MXene-based materials.展开更多
The adsorption of C atoms on the α-Fe2O3（001） surface was studied based on density function theory（DFT） ,in which the exchange-correlation potential was chosen as the PBE（Perdew,Burke and Ernzerhof） generalized...The adsorption of C atoms on the α-Fe2O3（001） surface was studied based on density function theory（DFT） ,in which the exchange-correlation potential was chosen as the PBE（Perdew,Burke and Ernzerhof） generalized gradient approximation（GGA） with a plane wave basis set. Upon the optimization on different adsorption sites with coverage of 1/20 and 1/5 ML,it was found that the adsorption of C atoms on the α-Fe2O3（001） surface was chemical adsorption. The coverage can affect the adsorption behavior greatly. Under low coverage,the most stable adsorption geometry lied on the bridged site with the adsorption energy of about 3.22 eV; however,under high coverage,it located at the top site with the energy change of 8.79 eV. Strong chemical reaction has occurred between the C and O atoms at this site. The density of states and population analysis showed that the s,p orbitals of C and p orbital of O give the most contribution to the adsorption bonding. During the adsorption process,O atom shares the electrons with C,and C can only affect the outermost and subsurface layers of α-Fe2O3; the third layer can not be affected obviously.展开更多
This paper presents new geological and geochemical data from the Shuanghu area in northern Tibet, which recorded the Early Toarcian Oceanic Anoxic Event. The stratigraphic succession in the Shuanghu area consists most...This paper presents new geological and geochemical data from the Shuanghu area in northern Tibet, which recorded the Early Toarcian Oceanic Anoxic Event. The stratigraphic succession in the Shuanghu area consists mostly of grey to dark-colored alternating oil shales, marls and mudstones. Ammonite beds are found at the top of the Shuanghu oil shale section, which are principally of early Toarcian age, roughly within the Harplocearas falciferrum Zone. Therefore, the oil shale strata at Shuanghu can be correlated with early Toarcian black shales distributing extensively in the European epicontinental seas that contain the records of an Oceanic Anoxic Event. Sedimentary organic matter of laminated shale anomalously rich in organic carbon across the Shuanghu area is characterized by high organic carbon contents, ranging from 1.8% to 26.1%. The carbon isotope curve displays the δ 13C values of the kerogen (δ 13Ckerogen) fluctuating from –26.22 to –23.53‰ PDB with a positive excursion close to 2.17‰, which, albeit significantly smaller, may also have been associated with other Early Toarcian Oceanic Anoxic Events (OAEs) in Europe. The organic atomic C/N ratios range between 6 and 43, and the curve of C/N ratios is consistent with that of the δ 13Ckerogen values. The biological assemblage, characterized by scarcity of benthic organisms and bloom of calcareous nannofossils (coccoliths), reveals high biological productivity in the surface water and an unfavorable environment for the benthic fauna in the bottom water during the Oceanic Anoxic Event. On the basis of organic geochemistry and characteristics of the biological assemblage, this study suggests that the carbon-isotope excursion is caused by the changes of sea level and productivity, and that the black shale deposition, especially oil shales, is related to the bloom and high productivity of coccoliths.展开更多
Aqueous E pH Diagram is an essential tool for analyzing hydrometallurgical and corrosion processes. Due to the requirements for environmental protection and energy saving in recent years, waste water processing a...Aqueous E pH Diagram is an essential tool for analyzing hydrometallurgical and corrosion processes. Due to the requirements for environmental protection and energy saving in recent years, waste water processing and hydrometallurgical process of concentrate have been greatly developed. The construction of E pH diagrams has turned to multi component systems. However, there are some limits in plotting such diagrams. There is only one diagram for one multi component system, which can not reflect the truth of the aqueous reaction. In the paper, a new computation method is proposed to construct E pH diagrams. Component activity term is used to determine the boundary of stable areas. For the multi component systems, different atom ratios of elements have been taken into account. M S H 2O system is chosen to study since it is of importance in metallurgical solution. Compared with conventional methods, the algorithm is simple and conforms to real conditions.展开更多
Tropical peat swamp forest beds that have been reclaimed for agricultural use are generally an active source of nitrous oxide （N2O） efflux, however, the mechanism by which reclaimed tropical peat soils promote the e...Tropical peat swamp forest beds that have been reclaimed for agricultural use are generally an active source of nitrous oxide （N2O） efflux, however, the mechanism by which reclaimed tropical peat soils promote the emergence of N2O emitters in soil microbial communities remains unclear. The purpose of this study was to reveal the vertical distribution of N2O emission potential and its correlation with mineral nitrogen contents in reclaimed soils. Using a culture-based N2O emission assay, the N2O emission potentials of soil at various depths （0-450 cm） were investigated in two oil palm plantations in Sarawak, Malaysia, which had elapsed times of two years （E2Y） and 10 years （El 0Y） after deforestation, respectively. On the basis of the relationship between the vertical profiles of N2O emission potentials and the contents of mineralized nitrogen in the peat soils at various depths, the impact of land management on soil microbial communities was discussed. The peat soil at plantation site E2Y showed a trend of high N2O production in deep layers （200-400 cm）, whereas the older plantation site E10Y showed considerably more active N2O emission in shallow soil （10-50 cm）. N2O emission potentials among the soil microbial communities at different soil depths at the E10Y site showed positive correlations with NO3- and NH4＋ contents, whereas, soils obtained from the E2Y site had N2O emission potentials that were inversely proportional to the contents of NO3-. This contrasting vertical correlation between N2O-emitting potentials and mineralized nitrogen contents in bulk soils suggests that active N2O emission in deep soil at the E2Y site has maintained the original carbon-nitrogen （C/N） ratio of the peat soil, whereas at EIOY, such a regulatory system has been lost due to advanced soil degradation, leading to dynamic changes in the nitrogen cycle in shallow soil.展开更多
文摘Formaldehyde(HCHO) is a common indoor pollutant, long-term exposure to HCHO may harm human health. Its efficient removal at mild conditions is still challenging. The catalytic oxidation of HCHO molecules on a single atomic catalyst, Ti-decorated Ti3C2O2(Ti/Ti3C2O2) monolayer, is investigated by performing the first principles calculations in this work. It demonstrates that Ti atoms can be easily well dispersed at the form of single atom on Ti3C2O2 monolayer without aggregation. For HCHO catalytic oxidation, both Langmuir-Hinshelwood(LH) and Eley-Rideal(ER) mechanisms are considered. The results show that the step of HCHO dissociative adsorption on Ti/Ti3C2O2 with activated O2 can release high energy of 4.05 e V based on the ER mechanism, which can help to overcome the energy barrier(1.04 e V) of the subsequent reaction steps. The charge transfer from *OH group to CO molecule(dissociated from HCHO) not only promotes *OH group activation but also plays an important role in the H2 O generation along the ER mechanism. Therefore, HCHO can be oxidized easily on Ti/Ti3C2O2 monolayer, this work could provide significant guidance to develop effective non-noble metal catalysts for HCHO oxidation and broaden the applications of MXene-based materials.
基金Project supported by the Foundation for Key Program of Ministry of Education (Nos.108033 and 107119)State Key Development Program for Basic Research of China (No.2009CB219801)+4 种基金the National High Technology Research and Development Program of China (No.2008AA05Z302)NNSFC (No.50976032)NSF of Beijing (No.3101001)the Specialized Basic Research Fund for Center Higher Education (No.09ZG03)Doctor Fund of North China Electric Power University (No.200822015)
文摘The adsorption of C atoms on the α-Fe2O3（001） surface was studied based on density function theory（DFT） ,in which the exchange-correlation potential was chosen as the PBE（Perdew,Burke and Ernzerhof） generalized gradient approximation（GGA） with a plane wave basis set. Upon the optimization on different adsorption sites with coverage of 1/20 and 1/5 ML,it was found that the adsorption of C atoms on the α-Fe2O3（001） surface was chemical adsorption. The coverage can affect the adsorption behavior greatly. Under low coverage,the most stable adsorption geometry lied on the bridged site with the adsorption energy of about 3.22 eV; however,under high coverage,it located at the top site with the energy change of 8.79 eV. Strong chemical reaction has occurred between the C and O atoms at this site. The density of states and population analysis showed that the s,p orbitals of C and p orbital of O give the most contribution to the adsorption bonding. During the adsorption process,O atom shares the electrons with C,and C can only affect the outermost and subsurface layers of α-Fe2O3; the third layer can not be affected obviously.
文摘This paper presents new geological and geochemical data from the Shuanghu area in northern Tibet, which recorded the Early Toarcian Oceanic Anoxic Event. The stratigraphic succession in the Shuanghu area consists mostly of grey to dark-colored alternating oil shales, marls and mudstones. Ammonite beds are found at the top of the Shuanghu oil shale section, which are principally of early Toarcian age, roughly within the Harplocearas falciferrum Zone. Therefore, the oil shale strata at Shuanghu can be correlated with early Toarcian black shales distributing extensively in the European epicontinental seas that contain the records of an Oceanic Anoxic Event. Sedimentary organic matter of laminated shale anomalously rich in organic carbon across the Shuanghu area is characterized by high organic carbon contents, ranging from 1.8% to 26.1%. The carbon isotope curve displays the δ 13C values of the kerogen (δ 13Ckerogen) fluctuating from –26.22 to –23.53‰ PDB with a positive excursion close to 2.17‰, which, albeit significantly smaller, may also have been associated with other Early Toarcian Oceanic Anoxic Events (OAEs) in Europe. The organic atomic C/N ratios range between 6 and 43, and the curve of C/N ratios is consistent with that of the δ 13Ckerogen values. The biological assemblage, characterized by scarcity of benthic organisms and bloom of calcareous nannofossils (coccoliths), reveals high biological productivity in the surface water and an unfavorable environment for the benthic fauna in the bottom water during the Oceanic Anoxic Event. On the basis of organic geochemistry and characteristics of the biological assemblage, this study suggests that the carbon-isotope excursion is caused by the changes of sea level and productivity, and that the black shale deposition, especially oil shales, is related to the bloom and high productivity of coccoliths.
文摘Aqueous E pH Diagram is an essential tool for analyzing hydrometallurgical and corrosion processes. Due to the requirements for environmental protection and energy saving in recent years, waste water processing and hydrometallurgical process of concentrate have been greatly developed. The construction of E pH diagrams has turned to multi component systems. However, there are some limits in plotting such diagrams. There is only one diagram for one multi component system, which can not reflect the truth of the aqueous reaction. In the paper, a new computation method is proposed to construct E pH diagrams. Component activity term is used to determine the boundary of stable areas. For the multi component systems, different atom ratios of elements have been taken into account. M S H 2O system is chosen to study since it is of importance in metallurgical solution. Compared with conventional methods, the algorithm is simple and conforms to real conditions.
文摘Tropical peat swamp forest beds that have been reclaimed for agricultural use are generally an active source of nitrous oxide （N2O） efflux, however, the mechanism by which reclaimed tropical peat soils promote the emergence of N2O emitters in soil microbial communities remains unclear. The purpose of this study was to reveal the vertical distribution of N2O emission potential and its correlation with mineral nitrogen contents in reclaimed soils. Using a culture-based N2O emission assay, the N2O emission potentials of soil at various depths （0-450 cm） were investigated in two oil palm plantations in Sarawak, Malaysia, which had elapsed times of two years （E2Y） and 10 years （El 0Y） after deforestation, respectively. On the basis of the relationship between the vertical profiles of N2O emission potentials and the contents of mineralized nitrogen in the peat soils at various depths, the impact of land management on soil microbial communities was discussed. The peat soil at plantation site E2Y showed a trend of high N2O production in deep layers （200-400 cm）, whereas the older plantation site E10Y showed considerably more active N2O emission in shallow soil （10-50 cm）. N2O emission potentials among the soil microbial communities at different soil depths at the E10Y site showed positive correlations with NO3- and NH4＋ contents, whereas, soils obtained from the E2Y site had N2O emission potentials that were inversely proportional to the contents of NO3-. This contrasting vertical correlation between N2O-emitting potentials and mineralized nitrogen contents in bulk soils suggests that active N2O emission in deep soil at the E2Y site has maintained the original carbon-nitrogen （C/N） ratio of the peat soil, whereas at EIOY, such a regulatory system has been lost due to advanced soil degradation, leading to dynamic changes in the nitrogen cycle in shallow soil.
