Enhancement Mechanism And Methods For Molecules Or Ions Adsorption In Porous Carbon Materials

Development of large-scale energy storage technology is the direction for solving the peak and valley difference in traditional power industry and and the intermittent shortcoming of new energy power generation technologies.Coal-fired power generation supports China's economic development,but at the same time brings serious environmental pollution.Carbon-based functional materials featuring both physical and chemical activity,are important adsorption media for gas molecules and liquid ion for both electrochemical energy storage and pollutant removal processes.Porous carbon-based electrochemical energy storage and contaminant control processes have a common scientific nature,namely,the adsorption,reaction,transport and storage of target species?molecules,ions,electrons?,the storage of material or energy in the pore structure of carbon materials is the common theme.High transport rate and storage capacity require well-developed activity;long cycle life requires high carbon structure stability;the contradiction between activity and stability is another key issue.This paper draws four key questions about the energy storage and pollut ant control of carbon materials:?1?Sulfur adsorption,conversion and migration mechanism in the nanopores of porous carbons;?2?Construction of nitrogen-containing defects in carbon materials and mechanism of ion adsorption enhancement;?3?Construction of boron-containing defects in carbon materials and mechanism of lithium ion storage enhancement;?4?Mesoporous structure homogeneously construction in carbon materials for synergistically enhancing the activity and stability of active lithium storage materials.Through studying the above four key issues,this paper aims to step-by-step reveal the influence mechanism and strengthening method for carbon based ion adsorption and storage,molecule adsorption and storage and multiphase adsorption catalysis.Based on the above studies,this paper proposes several strategies for synergistically enhancing the activity and stability of porous carbons,which lays the theoretical foundation for the development of advanced carbon-based pollutant control and energy storage technology.The adsorption process of SO₂ in actived coke involves the process of adsorption and oxidation of SO₂,the migration of intermediates and final products.In this paper,the effects of the pore structure and nitrogen-containing active sites on the adsorption of SO₂ molecules were firstly studied.The results show that micropores with pore size less than 0.7 nm are the main space for SO₂ physical adsorption.In order to accurately obtain the effect of nitrogen-containing active sites on the adsorption of SO₂,a series of carbon materials with the same pore structure parameters and different nitrogen contents were prepared and studied for the adsorption of SO₂.Combining the DFT calculation,this paper for this time reveals the enhancing mechanism of nitrogen-containing active sites on the SO₂ adsorption process.The calculation results indicate that the introduction of nitrogen-containing active sites changes the electron distribution of the carbon-based surface,which promotes the adsorption of SO₂ on the carbon-based surface,in particular,can promote the physical adsorption of SO₂ molecules on the carbon-based surface and the edge of carbon surface.Nitrogen atom itself is not the SO₂ point-to-point combination site.Based on the study of SO₂ separate adsorption,this paper further studied the mechanism of O₂ and H2 O in flue gas on SO₂ oxidation and sulfuric acid formation and migration.The results show that the SO₂ removal capacity in the presence of O₂ and H2 O is 7 times higher than that of SO₂ separate adsorption;the activated coke with hierarchically pore gives the best desulfurization performance;the mesopore and macropore connected structures provide the migration and storage space for desulfurization products SO3 and H2SO4.On the basis of the above research,this paper creatively proposed the SO3/H2SO4 polarity-induced migration mechanism.It is considered that the polar functional groups,distributing in mesopores of activated coke play a significant role in the SO₂ removal process.Polar functional groups act as the adsorption centers of polar molecules.Relying on polar effect or hydration,the byproduct SO3 or H2SO4 forming in micropores are able to migrate out of micropores and into mesopores or macropores in the form of liquid.The introduction of nitrogen defects in the carbon material could enhance the supercapacitor activity,however,non-uniform doping or surface doping can affect the carbon structure cycling stability.To solve the problem,this paper reports a novel nitrogen-rich carbon sphere?NRC?based on molecular self-assembly process assisted with aerosol spray process which is easy to amplify the production.The morphology,porosity and nitrogen defects can be synergistically regulated,which achieves molecule-scale embedding of nitrogen species into carbon structure with a high content.Through the correlation analysis between structure characterization results,electrochemical properties and the quantum chemical calculation results,this paper reveals the strengthening mechanism of nitrogen defects on ion transport and adsorption.The results indicate that the energy density of NRC-based supercapacitor is 3-5 times that of the commercial carbon-based double-layer supercapacitor and the cycling life is up to 10,000 times;nitrogen defects induce the surface polarity and non-uniform electron distribution and thus improve the ion diffusion and adsorption capability which leads to enhanced double-layer supercapacitive behavior.In view of the problem that the graphite anode has low lithium capacity and poor stability,this paper further employs molecular self-assembly technique and aerosol spray process to prepare boron-doped nanocarbon sphere by which the highly active and highly stable BC structure can be introduced into carbon structure.Strengthening mechanism of boron doping on lithium storage Activity and stability was systematically studied.The results indicate that boron doping greatly enhance the carbon based anode properties in terms of high lithium storage capacity,excellent rate capability and long lifespan.The constructed anode exhibits no capacity decay at high current density even after 3000 cycles,which represents the highest level among the reported carbon based anode materials.Through the correlation analysis between structure characterization results,electrochemical properties and the quantum chemical calculation results,the enhancing effect of boron doping on ion/electron conductivity,lithium ion adsorption capability and carbon structure stability were elucidated.The synergistic effects endow the boron-doped nanocarbon spheres with both high lithium storage activity and stability.Aiming at the problem of volume strain of active metal and metal oxide during charge and discharge cycles,this paper adopted a mesoporous carbon skeleton for coating with nano metal/metal oxide particles.The nano-confined growth mechanism of active materials in carbon framework was studied.The lithium storage characteristic of prepared nanocomposite was tested.Combing the morphology and structure characterizations,the enhancing mechanis m of mesoporous carbon coating on lithium storage activity and stability was obtained.The results indicate that the uniformly distributed mesoporous structure in carbon framework the ZnO or Sn particles in the composite to be nanocrystalline and dispersed uniformly.The lithium storage capacity and cycling property reach the highest level among reported similar metal/metal oxide based anode materials.The construction of homogeneous mesopores of carbon skeleton is the key to suppress the volumetric strain of active substances and improve the utilization of electrode in order to realize the synergistic enhancement of lithium storage activity and stability.