Preparation And Application Of Phthalonitrile Based Porous Carbon Materials

Heteroatom doped porous carbon materials are widely used in energy?supercapacitor,secondary cell and fuel cell,etc.?,environmental protection?CO₂ adsorption and sewage treatment,etc.?,catalysis and other fields due to their controllable pore structure,environmentally friendly,large specific surface area,stable physical and chemical properties,rich heteroatom and high conductivity.However,at present,the preparation procedure is tedious and the conditions are harsh.Therefore,it is great importance to develop a simple and scalable way of preparing porous carbon materials with high specific surface area,suitable pore size distribution and high heteroatom content.For this reason,new corresponding strategies were proposed in this paper.Firstly,N/O co-doped hierarchical porous carbon materials were synthesized by carbonization and activation at high temperature with KOH as the activator and the phthalonitrile resin as precursor,which was prepared by curing1,3-bis?3,4-dicyanophenoxy?benzene?DPPH?via zinc chloride/urea composite curing agent.In addition,in order to further simplify the preparation process,DPPH,urea and KOH were directly mixed and calcined at high temperature in nitrogen atmosphere,and N/O co-doped porous carbon materiasl can be prepared by one-pot method,where polymerization,carbonization and activation were realized in one step.?1?Phthalonitrile resin was prepared by using DPPH as raw material and zinc chloride/urea as composite curing agent,and then the graded porous carbon material with high specific surface area,developed pores and high N/O content was successfully prepared by adding DPPH resin as raw material and KOH as activator.The effect of curing temperature on the content of nitrogen of porous carbon materials was studied.It was found that the N content of porous carbon materials prepared by the precursor with curing temperature of 400^oC was the highest?4.97 wt%?;at the same time,the material exhibited a large surface area(2026 m² g^-1),a high percentage of micropores?0.9?,and a high O content?7.53 wt%?.In a three-electrode system using 1 M H₂SO₄ solution,it was found that the sample with 400 ^o C curing temperature showed the best electrical properties,with a specific capacitance of 567 F g^-1,low resistance and good rate performance.Using the resin cured at 400?as the precursor,the effect of KOH content on the pore structure and heteroatom doping of porous carbon materials was studied,it was found that with the increase of KOH,the N content was decreased,but the specific surface area was increased.The specific capacitance of the material was measured by the acid three electrode system.It was found that the best performance was obtained when the mass ratio of resin and KOH was 1:1.It is worth mentioning that the material showed high cycle stability at the same time,and the specific capacitance retention rate was 119%after 100000 cycles.?2?Herein,a scalable and straightforward strategy was introduced to synthesize N/O co-doped hierarchical porous carbons?DNKs?with large specific surface area,high pore volume,high microporosity,and high heteroatom content derived from an all-in-one DPPH with the assistant of potassium hydroxide and urea.In this facile and template-free method,all the raw materials were placed in the tube furnace,and the one-pot process involved polymerization,carbonization and activation.Urea and KOH were selected as the catalyst and activator of DPPH,and the synergistic effect of the two additives in the preparation of DPPH based porous carbon materials was explored:The addition of urea promoted the polymerization of cyano group in DPPH,at the same time,it can also improve the N content of porous carbon materials as its own nitrogen source,the N content of the samples prepared by adding urea and KOH was 1.07 wt%higher than that of the sample only added KOH;KOH was the key to pore formation,and the porous carbon materials prepared by adding urea only showed a dense surface with a specific surface area of only 140 m² g^-1,while the specific surface area of porous carbon material prepared by adding only KOH was 1012 m²g^-1;meanwhile,adding urea and KOH can play a synergistic activation role,and the specific surface area,pore volume and microporosity of materials were greatly improved,reaching1801 m² g^-1,0.89 m³ g^-11 and 0.9,respectively.The effect of activation temperature on the composition and pore structure of the material was further studied in this paper.Appropriately increasing the temperature was beneficial to increase the specific surface area and pore volume,but reduced the content of N.The carbon material prepared by the above method can be served as outstanding gas adsorbent and electrode material of super capacitor with high cycle stability.Due to its high nitrogen content?7.93 wt%?and suitable microporous structure,DNK@550?activation temperature is 550 ^oC?showed a very high adsorption capacity(7.27mmol g^-1)for CO₂ at 273 K?1 bar?.DNK@650 exhibited excellent electrochemical performance in the three electrode system of 1 M H₂SO₄ electrolyte.At 0.1 A g^-1,its specific capacitance was as high as 487 F g^-1,and it had very good cycle stability(at 20 A g^-1,the specific capacity remains at 103%after 100000 cycles).