Iron‐based pyrophosphates are attractive cathodes for sodium‐ion batteries due to their large framework,cost‐effectiveness,and high energy density.However,the understanding of the crystal structure is scarce and on...Iron‐based pyrophosphates are attractive cathodes for sodium‐ion batteries due to their large framework,cost‐effectiveness,and high energy density.However,the understanding of the crystal structure is scarce and only a limited candidates have been reported so far.In this work,we found for the first time that a continuous solid solution,Na_(4−α)Fe_(2+α)_(2)(P_(2)O_(7))_(2)(0≤α≤1,could be obtained by mutual substitution of cations at center‐symmetric Na3 and Na4 sites while keeping the crystal building blocks of anionic P_(2)O_(7) unchanged.In particular,a novel off‐stoichiometric Na_(3)Fe(2.5)(P_(2)O_(7))_(2)is thus proposed,and its structure,energy storage mechanism,and electrochemical performance are extensively investigated to unveil the structure–function relationship.The as‐prepared off‐stoichiometric electrode delivers appealing performance with a reversible discharge capacity of 83 mAh g^(−1),a working voltage of 2.9 V(vs.Na^(+)/Na),the retention of 89.2%of the initial capacity after 500 cycles,and enhanced rate capability of 51 mAh g^(−1)at a current density of 1600 mA g^(−1).This research shows that sodium ferric pyrophosphate could form extended solid solution composition and promising phase is concealed in the range of Na_(4−α)Fe_(2+α)_(2)(P_(2)O_(7))_(2),offering more chances for exploration of new cathode materials for the construction of high‐performance SIBs.展开更多
Carbonate-bearing fluids widely exist in different geological settings,and play important roles in transporting some elements such as the rare earth elements.They may be trapped as large or small fluid inclusions(with...Carbonate-bearing fluids widely exist in different geological settings,and play important roles in transporting some elements such as the rare earth elements.They may be trapped as large or small fluid inclusions(with the size down to<1μm sometimes),and record critical physical-chemical signals for the formations of their host minerals.Spectroscopic methods like Raman spectroscopy and infrared spectroscopy have been proposed as effective methods to quantify the carbonate concentrations of these fluid inclusions.Although they have some great technical advantages over the conventional microthermometry method,there are still some technical difficulties to overcome before they can be routinely used to solve relevant geological problems.The typical limitations include their interlaboratory difference and poor performance on micro fluid inclusions.This study prepared standard ion-distilled water and K_(2)CO_(3)aqueous solutions at different molarities(from 0.5 to 5.5 mol/L),measured densities,collected Raman and infrared spectra,and explored correlations between the K_(2)CO_(3)molarity and the spectroscopic features at ambient P-T conditions.The result confirms that the Raman O-H stretching mode can be used as an internal standard to determine the carbonate concentrations despite some significant differences among the correlations,established in different laboratories,between the relative Raman intensity of the C-O symmetric stretching mode and that of the O-H stretching mode.It further reveals that the interlaboratory difference can be readily removed by performing one high-quality calibration experiment,provided that later quantifying analyses are conducted using the same Raman spectrometer with the same analytical conditions.Our infrared absorption data were collected from thin fluid films(thickness less than~2μm)formed by pressing the prepared solutions in a Microcompression Cell with two diamond-II plates.The data show that both the O-H stretching mode and the O-H bending mode can be used as internal standards to determine the carbonate concentrations.Since the IR signals of the C-O antisymmetric stretching vibration of the CO32ion,and the O-H stretching and bending vibrations from our thin films are very strong,their relative IR absorbance intensity,if well calibrated,can be used to investigate the micron-sized carbonate-bearing aqueous fluid inclusions.This study establishes the first calibration of this kind,which may have some applications.Additionally,our spectroscopic data suggest that as the K_(2)CO_(3)concentration increases the aqueous solution forms more large water molecule clusters via more intense hydrogen-bonding.This process may significantly alter the physical and chemical behavior of the fluids.展开更多
Waste selective catalytic reduction(SCR)catalysts are potential environmental hazards.In this study,the recovery of vanadium and tungsten from waste SCR catalysts by K_(2)CO_(3)roasting and water leaching was investig...Waste selective catalytic reduction(SCR)catalysts are potential environmental hazards.In this study,the recovery of vanadium and tungsten from waste SCR catalysts by K_(2)CO_(3)roasting and water leaching was investigated.The roasting and leaching conditions were optimized:the leaching efficiencies of vanadium and tungsten were 91.19%and 85.36%,respectively,when 18 equivalents of K_(2)CO_(3)were added to perform the roasting at 900℃ for 2 h,followed by leaching at 90°C for 1 h.Notably,in the described conditions,the leaching rate of silicon was only 28.55%.Titanates,including K_(2)Ti_(6)O_(13)and KTi8017,were also produced.Si removal was achieved in 85%efficiency adjusting the pH to 9.5,and the Si impurity thus isolated was composed of amorphous Si.Tungsten and vanadium were precipitated using CaCl_(2).At pH 10 and following the addition of 0.10 mol of H_(2)O_(2)and 16 equivalents of CaCl_(2),the precipitating efficiencies of tungsten and vanadium were 96.89%and 99.65%,respectively.The overall yield of tungsten and vanadium was 82.71%and 90.87%,respectively.展开更多
基金National Natural Science Foundation of China,Grant/Award Numbers:21972108,U20A20249,U22A20438Changzhou Science and Technology Bureau,Grant/Award Number:CM20223017Innovation and Technology Commission(ITC)of Hong Kong,The Innovation&Technology Fund(ITF)with Project No.ITS/126/21。
文摘Iron‐based pyrophosphates are attractive cathodes for sodium‐ion batteries due to their large framework,cost‐effectiveness,and high energy density.However,the understanding of the crystal structure is scarce and only a limited candidates have been reported so far.In this work,we found for the first time that a continuous solid solution,Na_(4−α)Fe_(2+α)_(2)(P_(2)O_(7))_(2)(0≤α≤1,could be obtained by mutual substitution of cations at center‐symmetric Na3 and Na4 sites while keeping the crystal building blocks of anionic P_(2)O_(7) unchanged.In particular,a novel off‐stoichiometric Na_(3)Fe(2.5)(P_(2)O_(7))_(2)is thus proposed,and its structure,energy storage mechanism,and electrochemical performance are extensively investigated to unveil the structure–function relationship.The as‐prepared off‐stoichiometric electrode delivers appealing performance with a reversible discharge capacity of 83 mAh g^(−1),a working voltage of 2.9 V(vs.Na^(+)/Na),the retention of 89.2%of the initial capacity after 500 cycles,and enhanced rate capability of 51 mAh g^(−1)at a current density of 1600 mA g^(−1).This research shows that sodium ferric pyrophosphate could form extended solid solution composition and promising phase is concealed in the range of Na_(4−α)Fe_(2+α)_(2)(P_(2)O_(7))_(2),offering more chances for exploration of new cathode materials for the construction of high‐performance SIBs.
基金the DREAM project of MOST,China(Grant No.2016YFC0600408)the Strategic Priority Research Program(B)of Chinese Academy of Sciences(Grant No.XDB18000000)the Program of the National Mineral Rock and Fossil Specimens Resource Center from MOST,China.
文摘Carbonate-bearing fluids widely exist in different geological settings,and play important roles in transporting some elements such as the rare earth elements.They may be trapped as large or small fluid inclusions(with the size down to<1μm sometimes),and record critical physical-chemical signals for the formations of their host minerals.Spectroscopic methods like Raman spectroscopy and infrared spectroscopy have been proposed as effective methods to quantify the carbonate concentrations of these fluid inclusions.Although they have some great technical advantages over the conventional microthermometry method,there are still some technical difficulties to overcome before they can be routinely used to solve relevant geological problems.The typical limitations include their interlaboratory difference and poor performance on micro fluid inclusions.This study prepared standard ion-distilled water and K_(2)CO_(3)aqueous solutions at different molarities(from 0.5 to 5.5 mol/L),measured densities,collected Raman and infrared spectra,and explored correlations between the K_(2)CO_(3)molarity and the spectroscopic features at ambient P-T conditions.The result confirms that the Raman O-H stretching mode can be used as an internal standard to determine the carbonate concentrations despite some significant differences among the correlations,established in different laboratories,between the relative Raman intensity of the C-O symmetric stretching mode and that of the O-H stretching mode.It further reveals that the interlaboratory difference can be readily removed by performing one high-quality calibration experiment,provided that later quantifying analyses are conducted using the same Raman spectrometer with the same analytical conditions.Our infrared absorption data were collected from thin fluid films(thickness less than~2μm)formed by pressing the prepared solutions in a Microcompression Cell with two diamond-II plates.The data show that both the O-H stretching mode and the O-H bending mode can be used as internal standards to determine the carbonate concentrations.Since the IR signals of the C-O antisymmetric stretching vibration of the CO32ion,and the O-H stretching and bending vibrations from our thin films are very strong,their relative IR absorbance intensity,if well calibrated,can be used to investigate the micron-sized carbonate-bearing aqueous fluid inclusions.This study establishes the first calibration of this kind,which may have some applications.Additionally,our spectroscopic data suggest that as the K_(2)CO_(3)concentration increases the aqueous solution forms more large water molecule clusters via more intense hydrogen-bonding.This process may significantly alter the physical and chemical behavior of the fluids.
基金from the Fundamental Research Funds for the Central Universities(2010YH14).
文摘Waste selective catalytic reduction(SCR)catalysts are potential environmental hazards.In this study,the recovery of vanadium and tungsten from waste SCR catalysts by K_(2)CO_(3)roasting and water leaching was investigated.The roasting and leaching conditions were optimized:the leaching efficiencies of vanadium and tungsten were 91.19%and 85.36%,respectively,when 18 equivalents of K_(2)CO_(3)were added to perform the roasting at 900℃ for 2 h,followed by leaching at 90°C for 1 h.Notably,in the described conditions,the leaching rate of silicon was only 28.55%.Titanates,including K_(2)Ti_(6)O_(13)and KTi8017,were also produced.Si removal was achieved in 85%efficiency adjusting the pH to 9.5,and the Si impurity thus isolated was composed of amorphous Si.Tungsten and vanadium were precipitated using CaCl_(2).At pH 10 and following the addition of 0.10 mol of H_(2)O_(2)and 16 equivalents of CaCl_(2),the precipitating efficiencies of tungsten and vanadium were 96.89%and 99.65%,respectively.The overall yield of tungsten and vanadium was 82.71%and 90.87%,respectively.
