Preparation Of N-Containing Porous Carbons For CO₂ Capture And Electrochemical Investigation

Nitrogen-doped porous carbons have become a research hotspot in the field of energy and environment because of their low cost,high activity and excellent stability,and Nitrogen-doped porous carbon is usually obtained by the carbonization of nitrogen-rich precursors.However,there are still some technical difficulties in the actual preparation of nitrogen-doped porous carbons from nitrogen-rich precursors.Some nitrogen-contained sources possess poor performance as precursor to prepare carbons due to their structure and intrinsic defects.The superior thermal and chemical stability of zeolite Imidazolate Frameworks?ZIFs?with abundant nitrogen content make it an ideal candidate for the preparation of nitrogen-doped porous carbons.At the same time,combining with molecular sieve template method,the potential applications of nitrogen-containing porous carbons in carbon dioxide uptake and electrochemistry are explored.The main contents are as follows:Firstly,we accomplished the crystallization synthesis of ZIF-8 in the phase of deionized water.Then ZIF-8 was used as carbon precursor to prepare porous carbons Z-T?where T represents 600,800 and 1000?,respectively?which are rich in nitrogen species.Variation of carbonization temperatures,Z-800 has the highest specific surface area of 640.8 m²/g.The adsorption capacity of Z-800 to CO₂ reaches3.25 mmol/g at 0?,and the selectivity is S_Z-800=48.When carbonization temperature runs up to 1000?,Z-1000 exhibits better catalytic activity toward oxygen reduction reaction(onset potential E_Onset=0.81V vs RHE,limiting current density j_k=3.5 mA/cm²)due to the increase of conductivity and graphite nitrogen content.Secondly,we added amino acids to regulate the growth of ZIF-8 in aqueous solution to prepare AZIF,then carbonized the amino-functionalized AZIF at different temperatures to obtain N-doped carbon A-Z-T?where T represents 800 and 1000?,respectively?.Compared with porous carbons obtained by direct carbonization of ZIF-8 at identical temperature,A-Z-800 has higher specific surface area,wider pore size distribution and high CO₂ adsorption selectivity S_A-Z-800=75.Compared with Z-1000,the results indicated that A-Z-1000 contains a V_meso/V_micro ratio of 70.6%,higher than that of 31.5%for Z-1000,and higher graphite nitrogen content,which makes it exhibit better electrocatalytic activity toward oxygen reduction reaction(onset potential E_Onset=0.87V vs RHE,limiting current density j_k=4.25 mA/cm²).In order to investigate the effect of post-treatment with nitrogen source on the nitrogen doping species and capacitance performance of porous carbons,we prepared microporous carbon materials XPC-700 using molecular sieve 10X as template and furfuryl alcohol as extra carbon source.Then we carbonized it with melamine,and further tuned its pore structure by chemical activation with KOH to obtain multiporous nitrogen-doped carbon materials ANXC-T?where T represents 600,700,80?,respectively?.When in the 6 M KOH,ANXC-700 exhibits the capacitance of45.7 F/g at 0.1 A/g and 42.0 F/g at 10 A/g with 92%capacitance of initial capacitance as current density increased up to 100-fold,also exhibits excellent cycle stability at high current density with capacitance retention up to 91%at 10 A/g after 10000 cycles.The results provide clear evidence for the carbon frameworks with N-doping in the enhancement of electrochemical performance.