Fine-tuning of the coordination environment of single-atom catalysts(SACs)is effective to optimize their catalytic performances,yet it remains challenging due to the vulnerability of SACs.Herein,we report a new approa...Fine-tuning of the coordination environment of single-atom catalysts(SACs)is effective to optimize their catalytic performances,yet it remains challenging due to the vulnerability of SACs.Herein,we report a new approach to engineering the coordination environment of M-N-C(M=Fe,Co,and Ni)SACs by using glutamic acid as the N/C source and pyrolysis atmosphere as a regulator.Compared with that in N2,NH3 was able to promote the doping of N at 7<700℃yet etch the N-species at higher temperatures,by which the M-N coordination number(CN)and the electronic structure were delicately tuned.It was found that the electron density of Ni single atoms increased with the decrease of Ni-N CN.As a consequence,the capability of Ni-N-C to dissociate H2 was greatly enhanced and a higher catalytic activity in chemoselective hydrogenation of functionalized nitroarenes was achieved.Moreover,this modulation method could be applied to other transition metals including Fe and Co.In particular,the as-synthesized Co-N-C SAC afforded a turnover frequency of 152.3 h~1 with 99%selectivity to 3-vinylaniline in the hydrogenation of 3-nitrostyrene,which was the highest ever reported thus far and was at least one order of magnitude more active than state-of-the-art noble-metal-free M-N-C catalysts,demonstrating the great potential of engineering the coordination environment of SACs.展开更多
Supported metal-group materials are commonly utilized as state-of-the-art catalysts in industry.Atomic-sites catalysts(ASCs)have attracted increasing attention in catalysis owing to their 100%atom efficiency and uniqu...Supported metal-group materials are commonly utilized as state-of-the-art catalysts in industry.Atomic-sites catalysts(ASCs)have attracted increasing attention in catalysis owing to their 100%atom efficiency and unique catalytic performances toward various reactions.In particular,atomic dispersion of bulk and nano metals has become the focus of research and development in the synthesis of ASCs.Over the past decade,burgeoning interests have been paid to atomic dispersion in ASCs and their applications in catalysis.However,to the best of our knowledge,the systematic summary and analysis of atomic dispersion were rarely reported.In this review,recently developed ASCs by atomic dispersion were discussed in terms of synthetic atmosphere,driving force,applications in thermal catalytic reactions.Perspectives related to challenges and directions as well as design strategies of ASCs in atomic dispersion were also provided.展开更多
Descriptions of unusually high waves appearing on the sea surface for a short time (freak, rogue or killer waves) have been considered as a part of marine folklore for a long time. A number of instrumental registratio...Descriptions of unusually high waves appearing on the sea surface for a short time (freak, rogue or killer waves) have been considered as a part of marine folklore for a long time. A number of instrumental registrations have appeared recently making the community to pay more attention to this problem and to reconsider known observations of freak waves. To allow a better understanding of the behavior of rogue waves associated with tornadoes in terms of their origin, the nonlinear theory of off-balance systems is developed in the specific case of strong agitations constantly seen on the surface of extensive and deep rivers, when they are crossed by an atmosphere’s low pressure system (tornadoes, cyclones, hurricanes, etc.). A mathematical model based on the Navier-Stokes and Euler Lagrange equations coupled with assumptions derived from instrumental registrations on the training locations (or birth places) of freak waves is developed to enhance the physics of processes responsible for the formation (or origin) of the waves associated with atmosphere’s low pressure systems. Freak waves births’ constraints are mainly the need for both consistent water (i.e., extensive-deep rivers) and potential velocity flow availabilities. Numerical simulations, based on the use of the NLSE (Nonlinear Schrodinger Equation) are performed to validate our mathematical model on the births of single carrier waves associated with atmosphere’s low pressure systems.展开更多
基金supported by the National Key Technology R&D Program of China(No.2020YFA0710202)the National Natural Science Foundation of China(Nos.U1662130,21690080,21690084,and 21721004)the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDB17020100)。
文摘Fine-tuning of the coordination environment of single-atom catalysts(SACs)is effective to optimize their catalytic performances,yet it remains challenging due to the vulnerability of SACs.Herein,we report a new approach to engineering the coordination environment of M-N-C(M=Fe,Co,and Ni)SACs by using glutamic acid as the N/C source and pyrolysis atmosphere as a regulator.Compared with that in N2,NH3 was able to promote the doping of N at 7<700℃yet etch the N-species at higher temperatures,by which the M-N coordination number(CN)and the electronic structure were delicately tuned.It was found that the electron density of Ni single atoms increased with the decrease of Ni-N CN.As a consequence,the capability of Ni-N-C to dissociate H2 was greatly enhanced and a higher catalytic activity in chemoselective hydrogenation of functionalized nitroarenes was achieved.Moreover,this modulation method could be applied to other transition metals including Fe and Co.In particular,the as-synthesized Co-N-C SAC afforded a turnover frequency of 152.3 h~1 with 99%selectivity to 3-vinylaniline in the hydrogenation of 3-nitrostyrene,which was the highest ever reported thus far and was at least one order of magnitude more active than state-of-the-art noble-metal-free M-N-C catalysts,demonstrating the great potential of engineering the coordination environment of SACs.
基金Japan Society of Promotion of Science(JSPS)(Nos.P21354 and P22049).
文摘Supported metal-group materials are commonly utilized as state-of-the-art catalysts in industry.Atomic-sites catalysts(ASCs)have attracted increasing attention in catalysis owing to their 100%atom efficiency and unique catalytic performances toward various reactions.In particular,atomic dispersion of bulk and nano metals has become the focus of research and development in the synthesis of ASCs.Over the past decade,burgeoning interests have been paid to atomic dispersion in ASCs and their applications in catalysis.However,to the best of our knowledge,the systematic summary and analysis of atomic dispersion were rarely reported.In this review,recently developed ASCs by atomic dispersion were discussed in terms of synthetic atmosphere,driving force,applications in thermal catalytic reactions.Perspectives related to challenges and directions as well as design strategies of ASCs in atomic dispersion were also provided.
文摘Descriptions of unusually high waves appearing on the sea surface for a short time (freak, rogue or killer waves) have been considered as a part of marine folklore for a long time. A number of instrumental registrations have appeared recently making the community to pay more attention to this problem and to reconsider known observations of freak waves. To allow a better understanding of the behavior of rogue waves associated with tornadoes in terms of their origin, the nonlinear theory of off-balance systems is developed in the specific case of strong agitations constantly seen on the surface of extensive and deep rivers, when they are crossed by an atmosphere’s low pressure system (tornadoes, cyclones, hurricanes, etc.). A mathematical model based on the Navier-Stokes and Euler Lagrange equations coupled with assumptions derived from instrumental registrations on the training locations (or birth places) of freak waves is developed to enhance the physics of processes responsible for the formation (or origin) of the waves associated with atmosphere’s low pressure systems. Freak waves births’ constraints are mainly the need for both consistent water (i.e., extensive-deep rivers) and potential velocity flow availabilities. Numerical simulations, based on the use of the NLSE (Nonlinear Schrodinger Equation) are performed to validate our mathematical model on the births of single carrier waves associated with atmosphere’s low pressure systems.
