Preparation Of Transition Metal Carbon Nanocomposite And Its Electrochemical Catalysis And Energy Storage Research

The global energy crisis and environmental pollution are two of major issues humanity facing today.In the past few decades,scientists and engineers have worked hard to study and solve these two serious problems by developing new energy-related technologies such as wind and solar energy.Among them,energy conversion and storage are the key factors to achieve efficient and environmentally friendly use of renewable energy.Carbon nanomaterials,one of the forefront of hottest basic materials,have also become one of the important pillars for the advancement of contemporary science and technology,providing important material support and expansion potential for many industrial products.So far,the research on nanostructured materials with unique shapes and excellent properties has been rapidly developed,and has been widely used in nanoelectronic devices,energy materials,optoelectronic devices and biomedicine.Nanofibers are one of the most important nanostructures leading the way in nanoscience and nanotechnology.Among them,electrospinning technology has become a direct method for manufacturing nanofibers with high specific surface area,high porosity and controllable compositions.This paper mainly studies the application of different carbon nanomaterials in electrocatalysis and lithium ion batteries.?1?In this chapter,cobalt-based Prussian blue analogues?Co₃[Co?CN?₆]₂·nH₂O,abbreviated as Co-PB?were synthesized by chemical synthesis.The precursor solution was prepared by dispersed Co-PB and PAN,and then formed the Co-PB/PAN composite nanofiber by electrospin.The nanofibers were pre-oxidized and carbonized to form flexible3D Co@CNT-CNF carbon fiber films with carbon nanotubes grown on the surface.The flexible thin films obtained can be directly used as electrocatalytic electrodes for hydrogen evolution?HER?and oxygen evolution?OER?.A series of Co-PB composite carbon fiber materials were synthesized by exploring the different doping ratio of Co@CNT-CNF and the temperature conditions.The products with the optimum doping ratio of 10%and the optimum carbonization temperature of 1000°C were selected by the test.As a catalytic electrode for HER,the catalytic overpotential at a current density of 10 mA cm^-2 was 129 mV.As a catalytic electrode for OER,the catalytic potential was 162 mV at a current density of 10 mA cm^-2.At the same time,the membrane material was used in the water cracking of 1 mol L^-1KOH solution.For the whole water splitting experiment,the low overpotential of 1.53 V can achieve the current density of 10 mA cm^-2,and showed perfect electrocatalytic performance and high catalytic durability.This was mainly due to the large specific surface area,high conductivity and nano-porous composite structure of Co@CNT-CNF carbon fiber.?2?In this chapter,CoP@NC HNS hollow nanospheres,composed of ultrathin CoP@NC nanosheets doped with phosphorus and nitrogen,were prepared by designing SiO₂nanospheres as a sacrificial template.The synthesized hollow sphere has a size of about 320nm and a spherical shell thickness of about 40 nm.Owing to the carbon coating and nitrogen doping,the as-prepared CoP@NC HNS improved electrocatalysis performance towards the OER.Remarkably,the electrode based on these CoP@NC HNS attained a small overpotential of 320 mV(j=10 mA cm^-2),with a small Tafel slope of 68 mV dec^-1 and remarkable stability in alkaline electrolyte.When the temperature of the reaction went up to 60 ^oC,the catalytic performance was further improved(the overpotential about 290 mV at 10 mA cm^-2 and Tafel solpe=61 mV dec^-1).The excellent activity of CoP@NC HNS was possibly putted down to the nanoscopic CoP@NC interfaces in the heterostructure.The excellently active CoP@NC catalyst with low-cost,earth abundance and environmentally friendly is promising for future water splitting applications..?3?In this chapter,phytic acid?PA?was used as phosphorus and carbon source.The precursors containing phytic acid and iron were simply synthesized by precipitation method,and further FeP_x was synthesized by high temperature annealing.At the same time,the raw material was doped with graphene to synthesize FeP_x@C material,which was used as a high performance LIB anode material.Analysis of the results showed that the FeP_x and FeP_x@C composites provided lithium ion storage capacity of 637 and 818.3 mAh g^-1 at a current density of 100 mA g^-1.Phosphorus-doped carbon materials improved electrical conductivity and reduce volumetric changes in FeP_x during charge-discharge,maintaining structural integrity.In addition,based on its good lithium battery performance,the precursor was spun into nanofibers by electrospinning technology.It was pre-oxidized in air and carbonized at high temperature to form flexible FeP_x@CNF carbon nanofiber material,which was used as flexible lithium battery anode material.The results show the flexible carbon fiber provides a lithium ion storage capacity of 98.2 mAh g^-1 at a current density of 100 mA g^-1.