Adsorption And Conversion Of Carbon Dioxide Based On Porous Materials

The excessive use of fossil fuels has led to the increasing content of CO₂ in the atmosphere,so that the world is facing two major crises of energy shortage and climate warming.However,CO₂ is still a very important green carbon resource.Recycling it through capture and conversion technology can not only reduce the content of CO₂ from the root,help alleviate the greenhouse effect,but also transform CO₂ into recyclable high value-added chemical products such as CO,CH₄ and organic fuels,which is more conducive to alleviate the energy crisis.However,the current CO₂ capture and conversion technology has some problems,such as low adsorption capacity of adsorbent,high production cost,and low CO₂ conversion efficiency.In order to solve these problems,this paper prepared new porous materials by improving the synthesis process or combining with other porous materials,and finally achieved the purpose of improving the adsorption performance or conversion efficiency of CO₂gas.Firstly,commercial nano-CaCO₃ was used as a dual-functional template to prepare a high cost-performance hierarchical porous carbons(HPCs)based material with micro-mesoporous structure by carbonization of raw sugar,and its adsorption performance was studied as a CO₂ adsorbent.This work not only studied the effects of raw material ratio and carbonization temperature on the micro-mesoporous structure and adsorption properties of HPCs based materials,but also studied the importance of post activation behavior in the process of micropore formation and the optimal synthesis route for forming interconnected micro-mesoporous structure.The results revealed that the HPCs based materials excellent carbon dioxide uptake reaching up2.84 mmol/g(25 ^oC,1 bar),with micropore surface area of 786 m²/g,micropore volume of 0.320 cm³/g and mesopore volume of 0.233 cm³/g.After analysis,the reasons for the significant improvement of the adsorption performance of HPCs based materials mainly come from two aspects.On the one hand,the combination of carbonation reaction and internal activation reaction during the experiment can effectively induce the formation of regional micropores.On the other hand,the combination of nano-CaCO₃ incorporation and CO₂ post activation can not only effectively promote the formation of interconnected micro-mesoporous structures constructed by ultra-thin carbon walls,but also further improve its microporous structure and CO₂ adsorption performance.Secondly,the porous material zeolitic imidazolate frameworks(ZIF-8)was successfully loaded on Ti/TiO₂ NT by combining the anodic oxidation method and hydrothermal synthesis method to form the composite,and then it was decomposed or transformed by calcination method to form Ti/TiO₂ NT-ZIF-8 based composites material,which was used as the photoanode for the study of photoelectrocatalytic CO₂reduction performance.The effects of different calcination temperatures and external bias on CO₂ reduction ability of Ti/TiO₂ NT-ZIF-8 based composites material were studied.The experimental results show that,compared with the pure Ti/TiO₂ NT sample,the Ti/TiO₂ NT-ZIF-8-400?sample obtained after hydrothermal and calcination treatment showed good CO₂ reduction ability.The CO yield can reach12.9?mol cm^-2 and CH₄ yield can reach 3.36?mol cm^-2.The photoelectrocatalytic CO₂ reduction ability of Ti/TiO₂ NT-ZIF-8-400?has been significantly improved.This is mainly due to the fact that ZIF-8 is partially transformed into Zn O phase after calcination and forms semiconductor heterojunction with Ti/TiO₂ NT,which is beneficial to improve the photoelectric response ability of the material,and ultimately enhancing the photoelectrocatalytic CO₂ reduction efficiency.