Ni-ZIF-derived Porous Inorganic Metarials And Their Electrochemical Performances

Nowadays,the continuous consumption of energy and the worsening of environmental problems have aroused great concern of human beings.In recent years,researchers have made some progress in hydrogen evolution reaction and anode materials for metal ion batteries.For hydrogen evolution reaction（HER）,high efficiency electrocatalyst is a necessary condition to improve the conversion efficiency,but at present the best catalytic performance of catalysts for HER are still precious metals（Pt and Ir）.Therefore,it is very desirable to search for non-noble metal catalysts with low price.As one of metal ion battery,the lithium ion battery is developing rapidly and commercializing at present.However,owning to the low lithium resources and its unevenly distribution on Earth,researchers have begun to explore sodium/potassium ion batteries.Metal-organic frameworks（MOFs）derived materials are considered to be the best materials for electrocatalyst and metal ion battery due to their large specific surface area and pore size,unique electronic properties,adjustable active sites,and good conductivity.Under inert high temperature conditions,N-containing organic ligands in MOFs will form N-doped graphene at high temperature.And the resulting materials are very suitable for electrocatalysts and anode materials for metal ion batteries.Therefore,we design Ni-based MOFs-derived materials as electrocatalysts for HER and anode materials for sodium/potassium metal ion batteries.The specific work is as follows:1.The design and fabrication of low-cost,efficient,and robust electrocatalysts for the hydrogen evolution reaction is of great importance in accelerating the development of water electrolysis technology.Herein,Ni Ru alloys nanostructures embedded in nitrogen-doped carbon matrix（Ni Ru@NC）have been fabricated through a facile metal-organic frameworks-derived（MOFs-derived）strategy.Benefiting from their advantages in the unique structures and components,the resulting Ni Ru@NC possesses excellent activity and durability towards the reaction,which exhibits low overpotentials of 85 and 53 m V at 10 m A cm^-2 in acidic and alkaline electrolytes,respectively.2.Though nickel sulfides with high theoretical capacities have been demonstrated as promising anode materials for both sodium-ion batteries（SIBs）and potassium-ion batteries（PIBs）,they always suffer from some Problem such as volume expansion and inferior electronic conductivity,resulting in bad behavior（whatever capacity and stability）.In this work,we design and prepare Ni S nanosheets anchored on the inner surface of nitrogen-doped hollow carbon matrixes（h-Ni S@N-C）,which could provide much more exposed active sites for electrochemical reactions for both SIBs and PIBs.The void space in nitrogen-doped carbon matrixes not only could largely buffer volume expansion of Ni S nanosheets but also could storage electrolyte and shorten the diffusion distance for ions during the discharge/charge process.Benefiting from the unique structural features,h-Ni S@N-C exhibits a high sodium-storage capacity of 510 m Ah g^-1 for 200 times at 0.1A g^-1 and a long-term stability with a capacity(290 m Ah g^-1 for 1000 times even at 1 A g^-1).The h-Ni S@N-C also shows excellent reversible capacity of 500 m Ah g^-1for 200 cycles at 0.1 A g^-1 and shows good cycle stability performance(260 m Ah g^-1 at 1 A g^-1 over 1000 cycles)in the PIBs.Furthermore,the sodium-ion full-cell performance suggests the potential of practical application of h-Ni S@N-C for energy storage devices.3.Porous carbonaceous materials have been extensively explored as promising anodes for potassium-ion batteries（PIBs）,and their potassium storage capacities are always higher than the theoretical specific capacity(279 m Ah g^-1).However,the origin of the extra capacity for PIBs in porous carbonaceous materials is rarely explored.Moreover,the development of carbonaceous anodes with high specific capacities and long-term cycling stability for PIBs remains a major challenge.Herein,we synthesized nitrogen-doped porous carbon materials（NPCs）with abundant interconnected nanopores modified by abundant edge-doped N atoms to investigate the origin of the extra capacity for PIBs.As expected,the resulting NPCs-600displays outstanding electrochemical performance with a high reversible capacity(409 m Ah g^-1 at 0.1A g^-1for 200 cycles),excellent rate capability(235 m Ah g-1 at 5 A g^-1),and remarkable long-term cycling stability(168 m Ah g^-1at 5 A g^-1 after 10000cycles).The remarkable performance results from the nanopores grafted by edge-doped nitrogen atoms on the inner surface which can adsorb more K⁺to enhance the capacity of carbon materials.Furthermore,the density functional theory（DFT）calculations further demonstrate that edge-doped nitrogen atoms on the inner surface of nanopores facilitate to the sorption of K⁺,providing the extra capacity for PIBs.