Nitrogen-Metal Coordination Engineering And Its Relationship With The Electrocatalytic Activities Of Catalysts

The development of electrocatalytic hydrogen production and metal-air batteries is of great significance to the practical application of clean energy in the future.This paper provides several strategies for adjusting the nitrogen-metal coordination structures of the catalysts,which effectively adjusts the charge density of the metallic active sites such as Mo,Co,and Ru,thereby optimizing the adsorption energy of reaction intermediates,and facilitating the kinetic process of the reactions.The structure-activity relationship between nitrogen-metal coordination structures and electrocatalytic activity has been established.And the efficient and stable electrocatalysts is significant to reduce the use of precious metals.1.The 2H-Mo S₂/N-doped mesoporous graphene composite catalysts with adjustable interfacial N-Mo coordination types were prepared by laser irradiation and one-step hydrothermal method.It was found that the p H-universal HER activities of these electrocatalysts are positively correlated with the content of interfacial pyridinic N-Mo bonds,rather than other types of N-Mo bonds,predominantly accounting for the substantially enhanced p H-universal HER activities.Density functional theory（DFT）calculations have further verified that pyridinic N can effectively adjust the charge density of Mo atoms in the interfacial N-Mo bonds,and promote the hydrogen adsorption and water splitting process for p H-universal HER.Therefore,interfacial pyridinic N-Mo bonds are the main active sites for the series of catalysts.As expected,the best-performance composite catalyst（Mo S₂/NLG-3）exhibits high catalytic activities and long-term stability in all-p H conditions.2.The perovskite-type LaCoO₃ nanoparticles are loaded on the N-doped mesoporous graphene in situ to prepare LaCo O₃/N-doped mesoporous graphene composite catalysts.It is found that pyridinic N atoms are more likely to bond with Co atoms at the interface,and the ORR/OER activity of these electrocatalysts is related to the interfacial pyridinic N-Co bond content.Therefore,the construction of more interfacial pyridinic N-Co bonds is conducive to improving the bifunctional oxygen electrocatalytic performance of LaCo O₃.In addition,both experiments and DFT calculations further reveal that in Co₃O₄/N-doped graphene composite electrocatalysts,the surface oxygen vacancies introduced by laser irradiation can produce a synergistic effect with the interfacial Co-N bonds to effectively modulate the charge density of oxygen-vacant Co active sites.The synergistic effect can futher optimize the adsorption energies for intermediates based on the interfacial Co-N bonding,and in turn remarkably enhancing intrinsic ORR/OER activities.The optimized catalyst(Co₃O_4-x-97/NG)exhibits an excellent cyclic charge-discharge performance in zinc-air battery.3.S was doped into the single-atom electrocatalyst with Ru-N₄ coordination structures by the hydrothermal method and high-temperature pyrolysis method.It is found that the S atoms are coordinated with N atoms in the second shell of Ru single atoms instead of directly bonding with central Ru,and the Ru-N₄-S coordination is beneficial to further regulate the charge density of Ru single atoms,thereby optimizing the adsorption of reaction intermediates and reducing the overpotential of the ORR process.In the alkaline media,the optimized electrocatalyst（Ru-SAS/SNC）exhibits excellent ORR activity and stability,and it also has ideal discharge performance in Zn-air,Al-air,and Li-O₂ batteries.