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Advanced materials: metal to metal bonding helps metal atom level dispersion

wallpapers News 2020-10-21
The active components in the

monatomic catalyst can be exposed to the surface of the support to the greatest extent with nearly 100% atom utilization which can greatly improve the intrinsic catalytic activity of the active site. These monoatomic catalysts can be obtained by bottom-up or top-down methods. The bottom-up method is controllable but in the process of obtaining metal atoms the agglomeration of metal atoms should be considered. On the other h if we directly start from metal nanoparticles use them as the initial products we can obtain atom level dispersed metals by decomposition which can not only eliminate the worries about the formation of clusters particle by-products in the bottom-up method but also exp the application scope of single atom catalysts. At present the dispersion of atoms in the matrix can be enhanced by increasing the entropy of atoms. If the top-down dispersion process can be realized at lower temperature it will help to control the cost of this method exp the scope of application. Aiming at this problem Wang Jiacheng Liu Jianjun of Shanghai Institute of silicate Chinese Academy of Sciences Liu Zheng of Nanyang University of technology in Singapore have studied in detail the influence of RH Fe bond on the atom level dispersion of RH Fe metals using nitrogen doped hollow carbon spheres as the matrix. The experimental results show that Fe nanoparticles can not be decomposed without RH Fe bond remain in the state of nanoparticles; RH nanoparticles will be formed before heat treatment. In contrast the existence of RH Fe bond can not only maintain the atomic level dispersion of RH but also induce the atomic level dispersion of Fe particles at low temperature. Experiments combined with first principles calculations show that the formation of intermediate iron particle-fe-n4 can activate the surrounding C atoms to form C vacancies thus effectively capturing the RH ions in the solution; the trapped RH further bonds with the Fe atoms in iron particle-fe-n4 stripping the Fe atoms from the original Fe particles to achieve atomic level dispersion. Based on a series of electrochemical characterization these n-doped hollow spheres with stable RH Fe monoatomic sites have excellent catalytic activity for her. At the current density of 10 Ma cm-2 the overpotential is only 36 MV the Tafel slope is 26 MV dec-1. At the same time it has good cycle stability has better catalytic performance than commercial Pt / C. This study provides a new idea for the promotion of metal atom level dispersion process the design of efficient atom level dispersion catalysts.

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