Layered P2-type cathodes with high voltage,large capacity,and easy synthesis show great potential for developing sodium(Na)-ion batteries(NIBs).However,the P2–O2 phase transition makes their structural degradation an...Layered P2-type cathodes with high voltage,large capacity,and easy synthesis show great potential for developing sodium(Na)-ion batteries(NIBs).However,the P2–O2 phase transition makes their structural degradation and the Na^(+)/vacancy ordering lowers their redox kinetics.Here,we rationally propose a compositionally graded P2-type cathode,where nickel(Ni)and manganese(Mn)fractions decrease gradually,and cobalt(Co)content increases contiguously from the inside to the outside of a secondary particle.Inside these particles,the Ni/Mn-based compound delivers high capacity and high voltage.On the surface of particles,the Co/Mn-based solid solution offers a stable buffer matrix.Benefiting from these synergistic effects,this graded P2-type cathode shows the elimination of P2–O2 transformation even when charged to 4.4 V,which enables good structural stability,maintaining capacity retention reaching~80%within 300 cycles.Moreover,the Na^(+)/vacancy ordering superstructure is further suppressed,and the Na^(+)diffusion kinetics is significantly improved.The proposed graded structure with optimized chemical composition offers a new perspective for eliminating the unwanted phase transition and thus enhancing the electrochemistry of high-voltage layered cathodes for advanced NIBs.展开更多
The present work establishes a systematic approach based on the application of in-situ Fourier transform infrared spectroscopy （FTIR） for the investigation of the crystal structure, thermal stability, redox behavior...The present work establishes a systematic approach based on the application of in-situ Fourier transform infrared spectroscopy （FTIR） for the investigation of the crystal structure, thermal stability, redox behavior （temperature-programmed reduction/temperatureprogrammed re-oxidation） as well as the catalytic properties of Co3O4 thin films. The syntheses of Co3O4 were achieved by chemical vapor deposition in the temperature range of 400-500℃. The structure analysis of the as-prepared material revealed the presence of two prominent IR bands peaking at 544 cm-1 （υ1） and 650 cm-1 （υ2） respectively, which originate from the stretching vibrations of the Co-O bond, characteristic of the Co3O4 spinel. The lattice stability limit of Co3O4 was estimated to be above 650℃. The redox properties of the spinel structure were determined by integrating the area under the emission bands υ1 and υ2 as a function of the temperature. Moreover, Co3O4 has been successfully tested as a catalyst towards complete oxidation of dimethyl ether below 340 ℃. The exhaust gas analysis during the catalytic process by in situ absorption FTIR revealed that only CO2 and H2O were detected as the final products in the catalytic reaction. The redox behavior suggests that the oxidation of dimethyl ether over Co3O4 follows a Mars-van Krevelen type mechanism. The comprehensive application of in situ FTIR provides a novel diagnostic tool in characterization and performance test of catalysts.展开更多
Stable and flexible metal nanoparticles(NPs)with regeneration ability are critical for long-term operation of solid oxide electrolysis cells(SOECs).Herein,a novel perovskite electrode with stoichiometric Pr_(0.4)Sr_(0...Stable and flexible metal nanoparticles(NPs)with regeneration ability are critical for long-term operation of solid oxide electrolysis cells(SOECs).Herein,a novel perovskite electrode with stoichiometric Pr_(0.4)Sr_(0.6)Co_(0.125)Fe_(0.75)Mo_(0.125)O_(3)−δ(PSFCM)is synthesized and studied,which undergoes multiple redox cycles to validate its structural stability and NPs reversibility.The Co-Fe alloy has exsolved from the parent bulk under reducing atmosphere,and is capable of reincorporation into the parent oxide after re-oxidation treatment.During the redox process,we successfully manipulate the size and population density of the exsolved NPs,and find that the average particle size significantly reduces but the population density increases correspondingly.The electrode polarization resistance of the symmetric cell remains stable for 450 h,and even activates after the redox cycling,which may be attributed to the higher quantity and larger specific surface area of the regenerated Co-Fe alloy NPs.Moreover,the electrochemical performance towards carbon dioxide reduction reaction(CO_(2)RR)is evaluated,and the CO_(2)electrolyzer consisting of CoFe@PSCFM-Ce_(0.8)Sm_(0.2)O_(1.9)(SDC)dual-phase electrode exhibits an excellent current density of 1.42 A·cm^(−2)at 1.6 V,which reaches 1.7 times higher than 0.83 A·cm^(−2)for the pristine PSCFM electrode.Overall,with this flexible and reversible high-performance SOEC cathode material,new options and perspectives are provided for the efficient and durable CO_(2)electrolysis.展开更多
基金funded by the National Natural Science Foundation of China(No.52102252)the Natural Science Foundation of Shandong Province(No.ZR2021QB052)China Postdoctoral Science Foundation(No.2021T140268).
文摘Layered P2-type cathodes with high voltage,large capacity,and easy synthesis show great potential for developing sodium(Na)-ion batteries(NIBs).However,the P2–O2 phase transition makes their structural degradation and the Na^(+)/vacancy ordering lowers their redox kinetics.Here,we rationally propose a compositionally graded P2-type cathode,where nickel(Ni)and manganese(Mn)fractions decrease gradually,and cobalt(Co)content increases contiguously from the inside to the outside of a secondary particle.Inside these particles,the Ni/Mn-based compound delivers high capacity and high voltage.On the surface of particles,the Co/Mn-based solid solution offers a stable buffer matrix.Benefiting from these synergistic effects,this graded P2-type cathode shows the elimination of P2–O2 transformation even when charged to 4.4 V,which enables good structural stability,maintaining capacity retention reaching~80%within 300 cycles.Moreover,the Na^(+)/vacancy ordering superstructure is further suppressed,and the Na^(+)diffusion kinetics is significantly improved.The proposed graded structure with optimized chemical composition offers a new perspective for eliminating the unwanted phase transition and thus enhancing the electrochemistry of high-voltage layered cathodes for advanced NIBs.
文摘The present work establishes a systematic approach based on the application of in-situ Fourier transform infrared spectroscopy （FTIR） for the investigation of the crystal structure, thermal stability, redox behavior （temperature-programmed reduction/temperatureprogrammed re-oxidation） as well as the catalytic properties of Co3O4 thin films. The syntheses of Co3O4 were achieved by chemical vapor deposition in the temperature range of 400-500℃. The structure analysis of the as-prepared material revealed the presence of two prominent IR bands peaking at 544 cm-1 （υ1） and 650 cm-1 （υ2） respectively, which originate from the stretching vibrations of the Co-O bond, characteristic of the Co3O4 spinel. The lattice stability limit of Co3O4 was estimated to be above 650℃. The redox properties of the spinel structure were determined by integrating the area under the emission bands υ1 and υ2 as a function of the temperature. Moreover, Co3O4 has been successfully tested as a catalyst towards complete oxidation of dimethyl ether below 340 ℃. The exhaust gas analysis during the catalytic process by in situ absorption FTIR revealed that only CO2 and H2O were detected as the final products in the catalytic reaction. The redox behavior suggests that the oxidation of dimethyl ether over Co3O4 follows a Mars-van Krevelen type mechanism. The comprehensive application of in situ FTIR provides a novel diagnostic tool in characterization and performance test of catalysts.
基金supported by the National Natural Science Foundation of China(No.U21A20317)the National Key Research and Development Program of China(No.2022YFA1504701)+2 种基金the Fundamental Research Funds for the Central Universities(No.2042022gf0002)the start-up research funds from Wuhan Institute of Technology(No.K202201)Guangdong Basic and Applied Basic Research Foundation(No.2023A1515010429).
文摘Stable and flexible metal nanoparticles(NPs)with regeneration ability are critical for long-term operation of solid oxide electrolysis cells(SOECs).Herein,a novel perovskite electrode with stoichiometric Pr_(0.4)Sr_(0.6)Co_(0.125)Fe_(0.75)Mo_(0.125)O_(3)−δ(PSFCM)is synthesized and studied,which undergoes multiple redox cycles to validate its structural stability and NPs reversibility.The Co-Fe alloy has exsolved from the parent bulk under reducing atmosphere,and is capable of reincorporation into the parent oxide after re-oxidation treatment.During the redox process,we successfully manipulate the size and population density of the exsolved NPs,and find that the average particle size significantly reduces but the population density increases correspondingly.The electrode polarization resistance of the symmetric cell remains stable for 450 h,and even activates after the redox cycling,which may be attributed to the higher quantity and larger specific surface area of the regenerated Co-Fe alloy NPs.Moreover,the electrochemical performance towards carbon dioxide reduction reaction(CO_(2)RR)is evaluated,and the CO_(2)electrolyzer consisting of CoFe@PSCFM-Ce_(0.8)Sm_(0.2)O_(1.9)(SDC)dual-phase electrode exhibits an excellent current density of 1.42 A·cm^(−2)at 1.6 V,which reaches 1.7 times higher than 0.83 A·cm^(−2)for the pristine PSCFM electrode.Overall,with this flexible and reversible high-performance SOEC cathode material,new options and perspectives are provided for the efficient and durable CO_(2)electrolysis.
