The article is devoted to the study of ecological and geochemical features of interlayer waters of the Dnieper–Donetsk aquifer system in Ukraine,used for the potable water supply of Kyiv.A wide range of methods was u...The article is devoted to the study of ecological and geochemical features of interlayer waters of the Dnieper–Donetsk aquifer system in Ukraine,used for the potable water supply of Kyiv.A wide range of methods was used,including Microsoft Excel,Statistica,and Attestat software packages,MapInfo Professional 6.5 and ArcGIS-ArcMap 9.3 programs;the method of mass spectrometry with inductively coupled plasma(ICP-MS)and GEMS software were performed.Monitoring study results(during 2007–2023)were analyzed for two interlayer aquifers—Cenomanian-Callovian groundwater complex and Bajocian aquifer.It was determined that the normalized value of mineralization increased with a decrease in water intake during 1980–2010,which indicates a relative increase in the content of mineral substances during longterm exploitation.A high negative correlation(Kcor.=-0.54 to-0.86)is also typical for normalized values of oxidizability,total hardness,pH,Ca,Mg,and Cl content.Comparative analysis of two different aquifers revealed that the macrocomponent composition of Bajocian aquifer remains stable,once for Cenomanian-Callovian groundwater complex,there is a tendency to decrease hydrogen carbonates and increase chlorides and sulfates,whereas the cation composition remains relatively stable.A significant increase(by 55%)of the total mineralization in the representative well located on the right bank of the Dnieper River was found.There is also a significant increase(by more than 5 times)in the iron content,which the authors associate with the unsatisfactory technical condition of the well casing pipes.Physico-chemical modeling of trace elements,performed for investigated aquifers,shows that both aquifers are characterized by the predominant migration of the following metals in the cationic form(aqua-ions):Ca,Mg,Na,Ba,Co,Cu,Mn,Ni,Sr,Zn.It was found that the predominant migration forms of metals in the studied interlayer waters are free uncomplexed ions,carbonate,and hydroxo complexes.展开更多
Nickel-iron layered double hydroxides(NiFe LDHs) have been identified as one of the best promising electrocatalysts-candidates for oxygen evolution reaction(OER). However, the catalytic activity effected by interlayer...Nickel-iron layered double hydroxides(NiFe LDHs) have been identified as one of the best promising electrocatalysts-candidates for oxygen evolution reaction(OER). However, the catalytic activity effected by interlayer water molecules is ignored and rarely reported. Herein, Ni(OH)_2, NiFe LDHs vertically aligned Ni foam are designed for OER. As a contrast, the corresponding electrocatalysts with the removal of the interlayer water molecules(Ni(OH)_2-AT, NiFe LDHs-AT) are developed to probe into the influence of the interlayer water molecules towards OER. As expected, NiFe LDH nanoplates exhibit excellent catalytic performance and durability for water electrolysis in alkaline conditions with lower overpotential and smaller Tafel slope compared to those of NiFe LDHs-AT, which are influenced mainly by stability of crystal structure due to the existence of interlayer water molecules. The discovery opens up a similar pathway by controlling the amount of water molecules to boost catalytic performance for studying other electrocatalysts with heteroatom dopant.展开更多
In most cases, layered transition metal dichalcogenides (LTMDs), containing metallic phases, show electrochemical behavior different from their semiconductor counterparts. Typically, two-dimensional layered metallic...In most cases, layered transition metal dichalcogenides (LTMDs), containing metallic phases, show electrochemical behavior different from their semiconductor counterparts. Typically, two-dimensional layered metallic 1T-MoS2 demonstrates better electrocatalytic performance for water splitting compared to its 2H counterpart. However, the characteristics of low metallic phase concentration and poor stability limit its applications in some cases. Herein, we demonstrate a simple and efficient bottom-up wet-chemistry strategy for the large-scale synthesis of nanoscopic ultrathin Mo1-xWxS2 nanosheets with enlarged interlayer spacing and high metallic phase concentration. Our characterizations, including X-ray absorption fine structure spectroscopy (XAFS), high-angle annular dark-field- scanning transmission electron microscopy (HAADF-STEM), and X-ray photoelectron spectroscopy (XPS) revealed that the metallic ultrathin ternary Mo1-xWxS2 nanosheets exhibited distorted metal-metal bonds and a tunable metallic phase concentration. As a proof of concept, this optimized catalyst, with the highest metallic phase concentration (greater than 90%), achieved a low overpotential of about -155 mV at a current density of -10 ma/cm^2, a small Tafel slope of 67 mV/dec, and an increased turnover frequency (TOF) of 1.3 H2 per second at an overpotential of -300 mV (vs. reversible hydrogen electrode (RHE)), highlighting the importance of the metallic phase. More importantly, this study can lead to a facile solvothermal route to prepare stable and high-metallic- phase-concentration transition-metal-based two-dimensional materials for future applications.展开更多
基金financially supported by budget thematic of M.P.Semenenko Institute of Geochemistry,Mineralogy and Ore Formation of the NAS of Ukraine and the State Institution‘‘The Institute of Environmental Geochemistry of the National Academy of Sciences of Ukraine’’。
文摘The article is devoted to the study of ecological and geochemical features of interlayer waters of the Dnieper–Donetsk aquifer system in Ukraine,used for the potable water supply of Kyiv.A wide range of methods was used,including Microsoft Excel,Statistica,and Attestat software packages,MapInfo Professional 6.5 and ArcGIS-ArcMap 9.3 programs;the method of mass spectrometry with inductively coupled plasma(ICP-MS)and GEMS software were performed.Monitoring study results(during 2007–2023)were analyzed for two interlayer aquifers—Cenomanian-Callovian groundwater complex and Bajocian aquifer.It was determined that the normalized value of mineralization increased with a decrease in water intake during 1980–2010,which indicates a relative increase in the content of mineral substances during longterm exploitation.A high negative correlation(Kcor.=-0.54 to-0.86)is also typical for normalized values of oxidizability,total hardness,pH,Ca,Mg,and Cl content.Comparative analysis of two different aquifers revealed that the macrocomponent composition of Bajocian aquifer remains stable,once for Cenomanian-Callovian groundwater complex,there is a tendency to decrease hydrogen carbonates and increase chlorides and sulfates,whereas the cation composition remains relatively stable.A significant increase(by 55%)of the total mineralization in the representative well located on the right bank of the Dnieper River was found.There is also a significant increase(by more than 5 times)in the iron content,which the authors associate with the unsatisfactory technical condition of the well casing pipes.Physico-chemical modeling of trace elements,performed for investigated aquifers,shows that both aquifers are characterized by the predominant migration of the following metals in the cationic form(aqua-ions):Ca,Mg,Na,Ba,Co,Cu,Mn,Ni,Sr,Zn.It was found that the predominant migration forms of metals in the studied interlayer waters are free uncomplexed ions,carbonate,and hydroxo complexes.
基金financially supported by the National Natural Science Foundation of China (51622102, 51571124, 21421001)MOST (2017YFA0206702)+3 种基金the 111 Project (B12015)the Natural Science Foundation of Tianjin (16PTSYJC00030)the Fundamental Research Funds for the Central Universitiesthe Tianjin Colle ge Students Innovation and Entrepreneurship Training Project (201814038024)。
文摘Nickel-iron layered double hydroxides(NiFe LDHs) have been identified as one of the best promising electrocatalysts-candidates for oxygen evolution reaction(OER). However, the catalytic activity effected by interlayer water molecules is ignored and rarely reported. Herein, Ni(OH)_2, NiFe LDHs vertically aligned Ni foam are designed for OER. As a contrast, the corresponding electrocatalysts with the removal of the interlayer water molecules(Ni(OH)_2-AT, NiFe LDHs-AT) are developed to probe into the influence of the interlayer water molecules towards OER. As expected, NiFe LDH nanoplates exhibit excellent catalytic performance and durability for water electrolysis in alkaline conditions with lower overpotential and smaller Tafel slope compared to those of NiFe LDHs-AT, which are influenced mainly by stability of crystal structure due to the existence of interlayer water molecules. The discovery opens up a similar pathway by controlling the amount of water molecules to boost catalytic performance for studying other electrocatalysts with heteroatom dopant.
基金We acknowledge the financial support of the National Basic Research Program of China (Nos. 2014CB848900 and 2016YFA0200602), the National Natural Science Foundation of China (Nos. U1532112, 11375198, 11574280, and 21573204), CUSF (No. WK2310000053) and funds from Key Laboratory of Advanced Energy Materials Chemistry (Ministry of Education). L. S. thanks the recruitment program of global experts, the CAS Hundred Talent Program. We also thank the Shanghai synchrotron Radiation Facility (14W1, SSRF), the Beijing Synchrotron Radiation Facility (1W1B and soft-X-ray endstation, BSRF), the Hefei Synchrotron Radiation Facility (MCD and Photoemission Endstations, NSRL) and USTC Center for Micro and Nanoscale Research and Fabrication.
文摘In most cases, layered transition metal dichalcogenides (LTMDs), containing metallic phases, show electrochemical behavior different from their semiconductor counterparts. Typically, two-dimensional layered metallic 1T-MoS2 demonstrates better electrocatalytic performance for water splitting compared to its 2H counterpart. However, the characteristics of low metallic phase concentration and poor stability limit its applications in some cases. Herein, we demonstrate a simple and efficient bottom-up wet-chemistry strategy for the large-scale synthesis of nanoscopic ultrathin Mo1-xWxS2 nanosheets with enlarged interlayer spacing and high metallic phase concentration. Our characterizations, including X-ray absorption fine structure spectroscopy (XAFS), high-angle annular dark-field- scanning transmission electron microscopy (HAADF-STEM), and X-ray photoelectron spectroscopy (XPS) revealed that the metallic ultrathin ternary Mo1-xWxS2 nanosheets exhibited distorted metal-metal bonds and a tunable metallic phase concentration. As a proof of concept, this optimized catalyst, with the highest metallic phase concentration (greater than 90%), achieved a low overpotential of about -155 mV at a current density of -10 ma/cm^2, a small Tafel slope of 67 mV/dec, and an increased turnover frequency (TOF) of 1.3 H2 per second at an overpotential of -300 mV (vs. reversible hydrogen electrode (RHE)), highlighting the importance of the metallic phase. More importantly, this study can lead to a facile solvothermal route to prepare stable and high-metallic- phase-concentration transition-metal-based two-dimensional materials for future applications.