Metal oxides derived from metal-organic framework(MOF) have attracted considerable attention due to its excellent performance and unique structure. Doping is considered as an effective method to improve gas-sensing pe...Metal oxides derived from metal-organic framework(MOF) have attracted considerable attention due to its excellent performance and unique structure. Doping is considered as an effective method to improve gas-sensing performance. However, nonmetal doped metal oxides derived from MOF as gas-sensing materials have not been reported. Within this work, N atoms were successfully doped into the lattice of ZnO nanoparticles using ZIF-8 as a self-sacrificial template through a thermal treatment process with the assistant of urea. The obtained N-ZnO exhibited competitive ethanol-sensing performance, in which the response value of N-ZnO-5 to 100 ppm ethanol reached 115 at 190 ℃ with a satisfactory selectivity. It was found that the N-doping in ZnO facilitated the formation of oxygen vacancy that promoted the generation of adsorbed oxygen species to achieve the enhanced gas-sensing performance. Besides, the larger specific surface area resulting from the size reduction during the urea-assisted pyrolysis process can also be responsible for the improving of the ethanol-sensing performance.展开更多
By employing zinc acetate and sodium hydroxide as raw materials, ultrafine ZnO powders with different morphologies were successfully synthesized through hydrothermal method. The influences of the reaction temperature,...By employing zinc acetate and sodium hydroxide as raw materials, ultrafine ZnO powders with different morphologies were successfully synthesized through hydrothermal method. The influences of the reaction temperature, the OH-/Zn2＋ mol ratio and the reaction time on the morphologies of the ZnO powders were discussed. The reaction conditions were obtained, under which the ZnO of flower-like particles, micro-rods and flake particles was synthesized, respectively. The crystal structures and morphologies of those ZnO particles were characterized by X-ray diffraction （XRD） and scanning electron microscopy （SEM）. The ZnO with flower-like structures was composed of lots of micro-rods with hexagon morphology. The XRD patterns indicated that the ZnO powders were hexagonal wurtzite structures with high purity. Finally, the growth mechanism of the ZnO particles was discussed.展开更多
Based on the density functional theory （DFT）, using first-principles plane-wave ultrasoft pseudopotential method, the models of the unit cell of pure ZnO and two highly In-doped supercells of Zn0.9375In0.0625O and Z...Based on the density functional theory （DFT）, using first-principles plane-wave ultrasoft pseudopotential method, the models of the unit cell of pure ZnO and two highly In-doped supercells of Zn0.9375In0.0625O and Zn0.875In0.125O are constructed, and the geometry optimizations of the three models are carried out. The total density of states （DOS） and the band structures （BS） are also calculated. The calculation results show that in the range of high doping concentration, when the doping concentration is hihger than a specific value, the conductivity decreases with the increase of the doping concentration of In in ZnO, which is in consistence with the change trend of the experimental results.展开更多
ZnO thin films were deposited on n-Si （111） at various substrate temperatures by pulsed laser deposition （PLD）. X-ray diffraction （XRD）, photoluminescence （PL）, Fourier transform infrared spectrophotometer （F...ZnO thin films were deposited on n-Si （111） at various substrate temperatures by pulsed laser deposition （PLD）. X-ray diffraction （XRD）, photoluminescence （PL）, Fourier transform infrared spectrophotometer （FTIR）, and scanning electron microscopy （SEM） were used to analyze the structure, morphology, and optical property of the ZnO thin films. An optimal crystallized ZnO thin film was obtained at the substrate temperature of 600℃. A blue shift was found in PL spectra due to size confinement effect as the grain sizes decreased. The surfaces of the ZnO thin films were more planar and compact as the substrate temperature increased.展开更多
The discovery of efficient,selective,and stable electrocatalysts can be a key point to produce the largescale chemical fuels via electrochemical CO_(2) reduction(ECR).In this study,an earth-abundant and nontoxic ZnO-b...The discovery of efficient,selective,and stable electrocatalysts can be a key point to produce the largescale chemical fuels via electrochemical CO_(2) reduction(ECR).In this study,an earth-abundant and nontoxic ZnO-based electrocatalyst was developed for use in gas-diffusion electrodes(GDE),and the effect of nitrogen(N)doping on the ECR activity of ZnO electrocatalysts was investigated.Initially,a ZnO nanosheet was prepared via the hydrothermal method,and nitridation was performed at different times to control the N-doping content.With an increase in the N-doping content,the morphological properties of the nanosheet changed significantly,namely,the 2D nanosheets transformed into irregularly shaped nanoparticles.Furthermore,the ECR performance of Zn O electrocatalysts with different N-doping content was assessed in 1.0 M KHCO_(3) electrolyte using a gas-diffusion electrode-based ECR cell.While the ECR activity increased after a small amount of N doping,it decreased for higher N doping content.Among them,the N:ZnO-1 h electrocatalysts showed the best CO selectivity,with a faradaic efficiency(FE_(CO))of 92.7%at-0.73 V vs.reversible hydrogen electrode(RHE),which was greater than that of an undoped Zn O electrocatalyst(FE_(CO)of 63.4%at-0.78 V_(RHE)).Also,the N:ZnO-1 h electrocatalyst exhibited outstanding durability for 16 h,with a partial current density of-92.1 mA cm^(-2).This improvement of N:ZnO-1 h electrocatalyst can be explained by density functional theory calculations,demonstrating that this improvement of N:ZnO-1 h electrocatalyst comes from(ⅰ)the optimized active sites lowering the free energy barrier for the rate-determining step(RDS),and(ⅱ)the modification of electronic structure enhancing the electron transfer rate by N doping.展开更多
基金supported by the National Natural Science Foundation of China (Nos. 21806008, 21876008)Science and Technology General Project of Beijing Municipal Education Commission, China (No. KM202110016010)。
文摘Metal oxides derived from metal-organic framework(MOF) have attracted considerable attention due to its excellent performance and unique structure. Doping is considered as an effective method to improve gas-sensing performance. However, nonmetal doped metal oxides derived from MOF as gas-sensing materials have not been reported. Within this work, N atoms were successfully doped into the lattice of ZnO nanoparticles using ZIF-8 as a self-sacrificial template through a thermal treatment process with the assistant of urea. The obtained N-ZnO exhibited competitive ethanol-sensing performance, in which the response value of N-ZnO-5 to 100 ppm ethanol reached 115 at 190 ℃ with a satisfactory selectivity. It was found that the N-doping in ZnO facilitated the formation of oxygen vacancy that promoted the generation of adsorbed oxygen species to achieve the enhanced gas-sensing performance. Besides, the larger specific surface area resulting from the size reduction during the urea-assisted pyrolysis process can also be responsible for the improving of the ethanol-sensing performance.
基金supported by the National Natural Science Foundation of China (No. 51204054)the Fundamental Research Funds for the Central Universities, China (No.N110402012)
文摘By employing zinc acetate and sodium hydroxide as raw materials, ultrafine ZnO powders with different morphologies were successfully synthesized through hydrothermal method. The influences of the reaction temperature, the OH-/Zn2＋ mol ratio and the reaction time on the morphologies of the ZnO powders were discussed. The reaction conditions were obtained, under which the ZnO of flower-like particles, micro-rods and flake particles was synthesized, respectively. The crystal structures and morphologies of those ZnO particles were characterized by X-ray diffraction （XRD） and scanning electron microscopy （SEM）. The ZnO with flower-like structures was composed of lots of micro-rods with hexagon morphology. The XRD patterns indicated that the ZnO powders were hexagonal wurtzite structures with high purity. Finally, the growth mechanism of the ZnO particles was discussed.
基金the National Natural Science Foundation of China(Grant Nos.51261017 and 21261013)the Ministry of Education"Spring Sunshine" Plan Funding,China+1 种基金the Natural Science Foundation of Inner Mongolia Autonomous Region,China(Grant No.2011BS0104)the College Science Research Project of Inner Mongolia Autonomous Region,China(Grant Nos.NJZY12068 and NJZZ13099)
文摘Based on the density functional theory （DFT）, using first-principles plane-wave ultrasoft pseudopotential method, the models of the unit cell of pure ZnO and two highly In-doped supercells of Zn0.9375In0.0625O and Zn0.875In0.125O are constructed, and the geometry optimizations of the three models are carried out. The total density of states （DOS） and the band structures （BS） are also calculated. The calculation results show that in the range of high doping concentration, when the doping concentration is hihger than a specific value, the conductivity decreases with the increase of the doping concentration of In in ZnO, which is in consistence with the change trend of the experimental results.
基金This work was financially supported by the Key Research Program of National Natural Science Foundation of China (No. 90301002 and No. 90201025)
文摘ZnO thin films were deposited on n-Si （111） at various substrate temperatures by pulsed laser deposition （PLD）. X-ray diffraction （XRD）, photoluminescence （PL）, Fourier transform infrared spectrophotometer （FTIR）, and scanning electron microscopy （SEM） were used to analyze the structure, morphology, and optical property of the ZnO thin films. An optimal crystallized ZnO thin film was obtained at the substrate temperature of 600℃. A blue shift was found in PL spectra due to size confinement effect as the grain sizes decreased. The surfaces of the ZnO thin films were more planar and compact as the substrate temperature increased.
基金supported by the Basic Science Research Program through the National Research Foundation of Korea (NRF) (Grant Nos.2018R1A6A1A03024334,2019R1A2C1007637,2021M3I3A1082880,2021R1I1A1A01044174)the Basic Science Research Capacity Enhancement Project through Korea Basic Science Institute (Grant No.2019R1A6C1010024)。
文摘The discovery of efficient,selective,and stable electrocatalysts can be a key point to produce the largescale chemical fuels via electrochemical CO_(2) reduction(ECR).In this study,an earth-abundant and nontoxic ZnO-based electrocatalyst was developed for use in gas-diffusion electrodes(GDE),and the effect of nitrogen(N)doping on the ECR activity of ZnO electrocatalysts was investigated.Initially,a ZnO nanosheet was prepared via the hydrothermal method,and nitridation was performed at different times to control the N-doping content.With an increase in the N-doping content,the morphological properties of the nanosheet changed significantly,namely,the 2D nanosheets transformed into irregularly shaped nanoparticles.Furthermore,the ECR performance of Zn O electrocatalysts with different N-doping content was assessed in 1.0 M KHCO_(3) electrolyte using a gas-diffusion electrode-based ECR cell.While the ECR activity increased after a small amount of N doping,it decreased for higher N doping content.Among them,the N:ZnO-1 h electrocatalysts showed the best CO selectivity,with a faradaic efficiency(FE_(CO))of 92.7%at-0.73 V vs.reversible hydrogen electrode(RHE),which was greater than that of an undoped Zn O electrocatalyst(FE_(CO)of 63.4%at-0.78 V_(RHE)).Also,the N:ZnO-1 h electrocatalyst exhibited outstanding durability for 16 h,with a partial current density of-92.1 mA cm^(-2).This improvement of N:ZnO-1 h electrocatalyst can be explained by density functional theory calculations,demonstrating that this improvement of N:ZnO-1 h electrocatalyst comes from(ⅰ)the optimized active sites lowering the free energy barrier for the rate-determining step(RDS),and(ⅱ)the modification of electronic structure enhancing the electron transfer rate by N doping.
