Design Of Oxide With Hierarchical Structure And Its Gas-sensing Or Energy-storing Property

No matter applied in gas sensors or supercapacitors,the morphology of oxides has been the constant focus in corresponding fields,since the rational design of microstructure can enhance their performance effectively.Given this,a series of oxides with novel morphologies were successfully synthesized using a facile solvothermal or hydrothermal method,after which the gas-sensing or energy-storing properties were also analyzed carefully.Our work may provide a deeper understanding of the relationship between structure and performance,and may enlighten the design and fabrication of other kinds of materials.Details of our work are discussed below:Owing to the slenderness of the single spider silk and the fluffy arrangement of numerous monomers,the cobweb has the sufficient contact with the water vapor in air and can form dewdrops on it.Enlightened by this,WO₃ nanowires with a great length-diameter ratio and a non-compact assembly are inferred to possess an excellent gas-sensing property.As a proof-of-concept,the cobweb-like WO₃ was firstly synthesized through a facile solvothermal method using the water-ethanol mixed solution.The subsequent gas-sensing measurements testified this kind of cobweb-like WO₃ indeed displays an enhanced sensitivity towards the ethanol at a relatively low temperature.Nanorod arrays possess a large surface area due to the orderly arrangement of monomers,and thus are considered as an ideal microstructure to be utilized in the interface-related process such as the gas-sensing reaction.But their adoption is plagued by the complicated synthesis route in which the substrate is usually necessary.Here we propose a substrate-free fabrication of WO₃ nanorod arrays through the facile hydrothermal method.Subsequent measurements testify the superior NH₃-sensing property of WO₃ nanorod arrays.The corresponding response is as high as 8.3 at a concentration of 50 ppm and a temperature of 200?,surpassing other WO₃-based NH₃sensors reported.Composed of the heart,cardiac valves and blood vessels,the blood circulation system can manage the aggregation and the movement of the blood regularly and efficiently.Due to the analogical fluidity of the charge carrier and the blood,such system may act as the inspiration to design the advanced gas-sensing material.As a proof-of-concept,firstly,the porous WO₃ monomer was synthesized and recombined with the one-dimensional NiO monomer through the P-N junction to construct a similar structure.Subsequently,a series of gas-sensing tests towards the ethanol were measured.The obtained result indicates this nature-inspired nanocomposite indeed shows an enhanced gas-sensing property towards the ethanol,testifying the rationality of our design.The thorn-like surface can avert the compact stacking of nanoparticles through the mutual supporting of thorns.While the hollow structure can provide more active sites by the utilization of the inner surface.On account of these,we reported the facile synthesis of self-supporting MnCo₂O₄ hollow structures using a hydrothermal way and subsequent calcination.Fluorine-coordinated metal ions(Mn²⁺and Co²⁺)react with OH^-and CO₃^2-,generating the initial nanoparticles.Nanoparticles then go through a two-step assembly and a gas-driven deformation,ultimately forming the aforementioned morphology.In this process,the fluorine ion and the urea are regarded to play significant roles.The selection of electrode materials and the optimization of electrode configurations are two effective approaches to achieve high-performance energy storage.As a representative ternary metal oxide,CoMoO₄ has been directly grown on the carbon cloth via a facile hydrothermal method and subsequent calcination,forming a binder-free electrode.Further measurements reveal that this electrode is composed of CoMoO₄ nanosheets assembled 3D-framworks?NAFs?and thereby shows a superb electrochemical property in KOH solution.It is worth mentioning that the specific capacitance reaches as high as 1234 F/g at the current density of 1 A/g,which exceeds most of CoMoO₄ and CoMoO₄-based composites reported so far.Meanwhile,when the current density increases to 10 A/g,a considerable specific capacitance of 446 F/g is still obtained and can maintain nearly unchanged after 5000 cycles.