Construction And Property Studies Of Co-based Micro-/Nano-structures Derived From Metal Organic Frameworks

Owing to the excellent chemical and physical properties of metal-organic frameworks(MOFs),such as controllable pore structure,abundant active sites with unsaturated metal ions,high specific surface area,easy-modified channel surface and so on,they are used as matrices and templates for the preparation of micro/nano derivative structures using in different energy storage and conversion applications,such as lithium-ion batteries,lithium-sulfur batteries,metal-air batteries and water electrocatalysis.How to make full use of the advantages of MOF materials is still a great challenge to construct excellent electrode materials for electrocatalysis.Herein,we design to construct micro-nano derivative composite materials by controlling the composite,size and structure of MOF materials to improve the electrochemical performance.The main contents are summarized as followed:1.In Situ Anti-solvent Approach towards Novel Hydrangea-like HCo3O4-NC@CoNi-LDHs Core@shell Superstructures for Highly Efficient Water ElectrolysisDue to electronic transmission capacity and abundant redox reaction sites of Co3O4 supported on nitrogen-doped carbon substrate converted from MOF,and large specific surface area,and rich active sites of layered double hydroxide(LDH),in this chapter,we combine their characteristics and report an in situ anti-solvent approach for synthesizing ultrathin Co-Ni layered double hydroxide(CoNi-LDH)nanosheets wrapped on hollow Co3O4 nanoparticle-embedded nitrogen-doped carbon(HCo304-NC)as a high-performance catalyst for oxygen evolution reaction(OER).Although HCo3O4-NC or NiCo-LDH alone does not show good OER activity,their hybrid exhibits low overpotential and Tafel slope as well as high stability,which would be contributed to synergistic effect of Co304 and LDH.The hydrangea-like HCo3O4-NC@NiCo-LDH core@shell composite also exhibits higher catalytic activity and stability than the commercial IrO2,making it a high-performance non-precious metal-based catalyst for OER.2.Quantum-effect on Bimetallic-MOF for Construction of Two-dimensional Co3O4-embedded Nitrogen-doped Porous Carbon Nanosheet-arrays as Bifunctional Oxygen ElectrocatalystWith the decrease of material size,nanomaterial exhibits properties that are different from their counterpart bulk,which depend greatly on their dimension and morphology.In this chapter,we report an ammonia-modulating method for the synthesis of nanosized bimetallic ZnCo-ZIF.With ammonia amount increasing the size of ZnCo-ZIF crystals can be controlled to less than 10 nm.Owing to quantum effect the nanosized ZnCo-ZIF can be transformed into a well-aligned two-dimensional mono-crystalline Co3O4-embedded nitrogen-doped porous carbon nanosheet-arrays(2D-MCo3O4-NCNAs)as bi-functional electrocatalysts,which is totally different from the calcination product of microsized ZnCo-ZIF.These novel two-dimensional nanosheet-arrays lead to large active surface area,enhanced mass/charge transport capability,numerous active sites and strong structure stability.When used as bi-functional catalysts for oxygen reduction reaction(ORR)and oxygen evolution reaction(OER),the 2D-MCo3O4-NCNAs exhibit superior ORR activity as well as efficient OER activity in alkaline electrolyte,in comparison to the state-of-the-art precious metal catalysts.3.Formation of 2D-N-doped-PdO@CoO2-BCNSs from Prussian Blue Analogues by In-situ Ion Exchange with Enhanced OER and HER PerformancePrussian blue analogues have an open skeleton structure where the metal ions are readily interchanged with other ions.Noble metal Pd has similar crystal structure and lattice constant,as well as higher catalytic activity but lower price compared with Pt.In this chapter,Ni-Co PBA is used as template and precursor to be etched by ammonia.With the addition of palladium acetylacetonate,Pd2+ substituted for Ni2+ during the etching process.The original nanocube structure can be transformed into a unique butterfly-like nanosheet structure.Subsequently,it is calcined under N2 to obtain two-dimensional N-doped PdO@Co02 butterfly-like nanosheets(2D-N-doped-PdO@CoO2-BCNSs).It has many advantages such as large specific surface area and plentiful pore structures,which has been explored as OER and HER catalysts,showing excellent catalytic activity.