Inspired by molecular catalysts,researchers developed atomically precise nitrogen-coordinated single or dual metal sites imbedded in graphitized carbon(M-N-C)to fully utilize metallic sites for 02activation.These cata...Inspired by molecular catalysts,researchers developed atomically precise nitrogen-coordinated single or dual metal sites imbedded in graphitized carbon(M-N-C)to fully utilize metallic sites for 02activation.These catalysts performed remarkably well in the electrocatalytic oxygen reduction reaction(ORR)due to their distinct coordination and electrical structures,Nonetheless,their maximum efficacy in practical applications has yet to be achieved.This agenda identifies tailoring the coordination environment,spin states,intersite distance,and metal-metal interaction as innovative approaches to regulate the ORR performance of these catalysts.However,it is necessary to undertake a precise assessment of these methodologies and the knowledge obtained to be implemented in the design of future M-N-C catalysts for ORR.Therefore,this review aims to analyze recent progress in M-N-C ORR catalysts,emphasizing their innovative engineering with aspects such as alteration in intersite distance,metal-metal interaction,coordination environment,and spin states.Additionally,we critically discuss how to logically monitor the atomic structure,local coordination,spin,and electronic states of M-N-C catalysts to modulate their ORR activity.We have also highlighted the challenges associated with M-N-C catalysts and proposed suggestions for their future design and fabrication.展开更多
Single-atom catalysts(SACs)have been a research hotspot due to their high catalytic activity,selectivity,and atomic utilization rates.However,the theoretical research of SACs is relatively fragmented,which restricts f...Single-atom catalysts(SACs)have been a research hotspot due to their high catalytic activity,selectivity,and atomic utilization rates.However,the theoretical research of SACs is relatively fragmented,which restricts further understanding of SAC stability and activity.To address this issue,we report our analysis of the geometric structures,electronic characteristics,stabilities,catalytic activities,and descriptors of 132 graphene-based singleatom catalysts(M/GS)obtained from density functional theory calculations.Based on the calculated formation and binding energies,a stability map of M/GS was established to guide catalyst synthesis.The effects of metal atoms and support on the charge of metal atoms are discussed.The catalytic activities of M/GS in both nitrogen and oxygen reduction reactions are predicted based on the calculated magnetic moment and the adsorption energy.Combined with the electronegativity and d-band center,a two-dimensional descriptor is proposed to predict the O adsorption energy on M/GS.More importantly,this theoretical study provides predictive guidance for the preparation and rational design of highly stable and active single-atom catalysts using nitrogen doping on graphene.展开更多
This paper presents a new method for extract three-dimensional （3D） discrete spherical Fourier descriptors based on surface curvature voxels for pollen particle recognition. In order to reduce the high amount of pol...This paper presents a new method for extract three-dimensional （3D） discrete spherical Fourier descriptors based on surface curvature voxels for pollen particle recognition. In order to reduce the high amount of pollen information and noise disturbance, the geometric normalized curvature voxels with the principal curvedness are first extracted to represent the intrinsic pollen volumetric data. Then the curvature voxels are decomposed into radial and angular components with spherical harmonic transform in spherical coordinates. Finally the 3D discrete Fourier transform is applied to the decomposed curvature voxels to obtain the 3D spherical Fourier descriptors for pollen recognition. Experimental results show that the presented descriptors are invariant to different pollen particle geometric transformations, such as pose change and spatial rotation, and can obtain high recognition accuracy and speed simultaneously.展开更多
Knowledge of genetic relatedness among accessions of germplasm is necessary for the development of breeding strategies to produce improved cultivars. The present investigation on Hippophae rhamnoides was carried out t...Knowledge of genetic relatedness among accessions of germplasm is necessary for the development of breeding strategies to produce improved cultivars. The present investigation on Hippophae rhamnoides was carried out to assess its genetic variability in Himachal Pradesh, India, by employing morphological and RAPD markers. Different areas of Himachal Pradesh were surveyed and eight sites were finally selected Twenty four genotypes were selected for further studies, i.e., three genotypes from each site. On the basis of morphological studies, the genotypes of the Ropa site （Kinnaur） were considered elite genotypes. To assess the variability at the molecular level, RAPD patterns were studied by random primers. The total number of bands amplified was 607, out of which 487 bands were identified as polymorphic, depicting 80.23 per cent variability. Six unique bands were produced from three primers （OPA- 05, OPA-10 and OPD-08） specific for five genotypes, including three genotypes of the Ropa site, Kinnaur District.展开更多
基金supported by the Research Fund for International Scientists(RFIS-Grant numbers:52150410410)National Natural Science Foundation of Chinathe Deanship of Scientific Research and Graduate Studies at King Khalid University for funding this research work through Large Research Project under the grant number RGP2/121/1445.
文摘Inspired by molecular catalysts,researchers developed atomically precise nitrogen-coordinated single or dual metal sites imbedded in graphitized carbon(M-N-C)to fully utilize metallic sites for 02activation.These catalysts performed remarkably well in the electrocatalytic oxygen reduction reaction(ORR)due to their distinct coordination and electrical structures,Nonetheless,their maximum efficacy in practical applications has yet to be achieved.This agenda identifies tailoring the coordination environment,spin states,intersite distance,and metal-metal interaction as innovative approaches to regulate the ORR performance of these catalysts.However,it is necessary to undertake a precise assessment of these methodologies and the knowledge obtained to be implemented in the design of future M-N-C catalysts for ORR.Therefore,this review aims to analyze recent progress in M-N-C ORR catalysts,emphasizing their innovative engineering with aspects such as alteration in intersite distance,metal-metal interaction,coordination environment,and spin states.Additionally,we critically discuss how to logically monitor the atomic structure,local coordination,spin,and electronic states of M-N-C catalysts to modulate their ORR activity.We have also highlighted the challenges associated with M-N-C catalysts and proposed suggestions for their future design and fabrication.
基金the National Natural Science Foundation of China(No.91545122)Beijing Natural Science Foundation(2182066)+1 种基金Natural Science Foundation of Hebei Province of China(B2018502067)the Fundamental Research Funds for the Central Universities(2017XS121).
文摘Single-atom catalysts(SACs)have been a research hotspot due to their high catalytic activity,selectivity,and atomic utilization rates.However,the theoretical research of SACs is relatively fragmented,which restricts further understanding of SAC stability and activity.To address this issue,we report our analysis of the geometric structures,electronic characteristics,stabilities,catalytic activities,and descriptors of 132 graphene-based singleatom catalysts(M/GS)obtained from density functional theory calculations.Based on the calculated formation and binding energies,a stability map of M/GS was established to guide catalyst synthesis.The effects of metal atoms and support on the charge of metal atoms are discussed.The catalytic activities of M/GS in both nitrogen and oxygen reduction reactions are predicted based on the calculated magnetic moment and the adsorption energy.Combined with the electronegativity and d-band center,a two-dimensional descriptor is proposed to predict the O adsorption energy on M/GS.More importantly,this theoretical study provides predictive guidance for the preparation and rational design of highly stable and active single-atom catalysts using nitrogen doping on graphene.
基金Project supported by the National Natural Science Foundation of China (Grant No. 60472061)the Natural Science Foundation of Jiangsu Province,China (Grant No. BK20090149)the Natural Science Foundation of Higher Education Institutions of Jiangsu Province,China (Grant No. 08KJD520019).
文摘This paper presents a new method for extract three-dimensional （3D） discrete spherical Fourier descriptors based on surface curvature voxels for pollen particle recognition. In order to reduce the high amount of pollen information and noise disturbance, the geometric normalized curvature voxels with the principal curvedness are first extracted to represent the intrinsic pollen volumetric data. Then the curvature voxels are decomposed into radial and angular components with spherical harmonic transform in spherical coordinates. Finally the 3D discrete Fourier transform is applied to the decomposed curvature voxels to obtain the 3D spherical Fourier descriptors for pollen recognition. Experimental results show that the presented descriptors are invariant to different pollen particle geometric transformations, such as pose change and spatial rotation, and can obtain high recognition accuracy and speed simultaneously.
文摘Knowledge of genetic relatedness among accessions of germplasm is necessary for the development of breeding strategies to produce improved cultivars. The present investigation on Hippophae rhamnoides was carried out to assess its genetic variability in Himachal Pradesh, India, by employing morphological and RAPD markers. Different areas of Himachal Pradesh were surveyed and eight sites were finally selected Twenty four genotypes were selected for further studies, i.e., three genotypes from each site. On the basis of morphological studies, the genotypes of the Ropa site （Kinnaur） were considered elite genotypes. To assess the variability at the molecular level, RAPD patterns were studied by random primers. The total number of bands amplified was 607, out of which 487 bands were identified as polymorphic, depicting 80.23 per cent variability. Six unique bands were produced from three primers （OPA- 05, OPA-10 and OPD-08） specific for five genotypes, including three genotypes of the Ropa site, Kinnaur District.
