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Advanced materials: structural polarization of electrocatalysts and synchrotron radiation analysis of monodisperse active site injection

wallpapers News 2020-12-06
As one of the most important clean energy sources in the future hydrogen is the most important part of the earth's energy structure. Electrocatalytic decomposition of water to produce hydrogen is considered as a promising way to obtain hydrogen. So far many reported electrocatalysts have shown excellent performance in electrolyzing water in acidic medium but the development of low-cost electrocatalysts with high activity under alkaline conditions is still facing challenges. One of the main reasons is that the overall catalytic efficiency of hydrogen evolution reaction is low due to the high energy barrier of hydrolysis separation. In addition in order to achieve a more efficient separation of hydrogen molecules the adsorbed hydrogen produced by hydrolysis also needs to have a more appropriate desorption kinetic process. In recent years the electronic structure control of

catalysts has been considered as an effective strategy to enhance their electrocatalytic activity. For example nitrogen or manganese doped cobalt disulfide can optimize the free energy of hydrogen adsorption on active sites. In addition subjectively introducing hydrogen evolution active sites to some carriers is also a feasible strategy. Therefore how to inject high-density monatomic sites into suitable supports to achieve high atomic utilization (especially for noble metals) better catalytic properties at the same time has attracted researchers' attention. However it is still a great challenge to achieve high-density loading monatomic dispersion at the same time especially for non carbon based supports including hydroxides oxides nitrides sulfides Phosphates etc.

Professor Song Li's research group successfully anchored the noble metal Ru ion to the metal vacancy rich Ni (OH) 2 by impregnation method obtained the single atom Ru site doped ni5p4 electrocatalyst by phosphating treatment analyzed the structure of the catalyst by synchrotron radiation X-ray photoelectron spectroscopy absorption spectroscopy. Electrochemical tests show that ni5p4 doped with Ru site can achieve more efficient catalytic activity for hydrogen evolution in alkaline solution with a starting potential of 35mV a current density of 10macm-2 at an overpotential of 123mv with good stability. By loading the catalyst onto a large collector (carbon paper) the overall catalytic activity was further improved the over potential of 54 MV was finally achieved which was close to the activity of commercial Pt / C catalyst. Using X-ray absorption spectroscopy theoretical calculation the phenomenon of local structure polarization caused by Ru site doping is revealed: the local structure polarization brings about electron rich Ru sites which greatly promotes the occurrence of hydrolysis stepping the local structure related to Ru doping is also more favorable for the desorption process of adsorbed hydrogen. In addition when H2O dissociates at the Ru site the dissociated species will quickly transfer to the nearby site which also brings great help to the release of Ru site. The strategy of structure control active site injection introduced in this work is expected to be a universal method for the design of efficient electrocatalysts which will be widely studied applied in improving the performance of catalysts. At the same time there is still great potential for synchrotron radiation in-situ analysis method to be used in the characterization of electrocatalyst operado. The related work of

is supported by the key R & D program of the Ministry of science technology of the people's Republic of China the National Natural Science Foundation of the people's Republic of China (NSFC) the joint fund for large science installations the international partnership program of the Chinese Academy of Sciences the collaborative innovation of Hefei large science center.

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