Structural Control,Surface Functionalization And Electrocatalytic Application Of Porous Carbons

Porous carbon is a new kind of carbon material with high electronic transmission ability,large specific surface area,good mechanical strength and various structures.All these advantages are conducive to the electron/mass transmission,homogeneously dispersing electrocatalytic active sites and then boosting the catalytic efficiency of porous carbon based hybrid catalysts.Especially,for some electrochemical reactions with gaseous products appearing in the reaction processes（oxygen evolution reaction（OER）and hydrogen evolution reaction（HER））,the abundant open and out-plan macropores can also facilitate the release of gas bubbles from catalyst surfaces.This progress is conducive to renewal and recycle of active sites dispersed on catalyst surfaces,which can comparatively promote the catalytic actives and stabilities of hierarchically porous carbon based hybrid electrocatalysts.The functionalized porous carbons by different active sites,as the novel catalysts,demonstrate huge application potential in energy conversion devices,electrochemical energy storage devices and electrochemical sensors.In the introduction section,the kinds,methods for synthesis,methods for the functionalization and the electrochemical application of porous carbons were summarized.Specially,the synthesis methods of porous carbons,functionalization methods for porous carbons and electrochemical application of functionalized porous carbons in various fields are introduced in detail.Through designing and regulating structures of carbons,we have constructed a series of hierarchically porous carbons.After functionalizing them by some special active centers,some novel catalysts were successfully prepared and used in various catalysis reactions.Meanwhile,these hierarchically porous hybrid catalysts respectively show excellent catalysis activities for ORR,OER,HER or glucose oxidation/detection.At last,this dissertation consists of the following six aspects:（1）A series of cobalt and nitrogen co-embedded onion-like mesoporous carbon vesicles（Co–NMCV）were synthesized by the typical soft template method as non-noble metal catalysts for the first time.After optimizing the Co dosages in precursor,the optimal Co10-NMCV display the lamellar porous shell structures accompanying a considerable surface area and a large pore volume.Meantime,large amounts of Co-N-C species are uniformly dispersed along the surfaces of Co10-NMCV.Electrochemically experimental results indicated that the optimal Co10-NMCV shows excellent ORR catalysis activities in both acidic and alkaline electrolytes.Co10–NMCV catalyst also shows higher durability of the ORR catalytic activity and better methanol tolerance than the commercial Pt/C catalyst.（2）In order to study the roles of pores with different pore diameters in boostingelectrocatalytic activities of carbon hybrid materials,imporous graphene oxide（GO）,macroporous carbon（MPC）,mesoporous carbon vesicles（MCVs）and ordered mesoporous carbon（OMC）with open structures were synthesized and adopted as carbon matrices for loading Co3O4 and CoP nanoparticles（NPs）respectively.Because of the abundant open porous channels,large specific surface area,and more carbon edges/defects of OMC matrix,Co3O4 and CoP NPs dispersed and embedded on surfaces of OMC matrix without using any extreme conditions and harmful organic reagents or surfactants.As the high electron/mass transinformation rates and abundant active site exposures degree for both Co3O4-OMC and CoP-OMC,when they are used for catalyzing glucose oxidation and HER respecially,Co3O4-OMC displays excellent glucose oxidation efficiency and CoP-OMC affords outstanding HER catalysis activity and long-term stability.（3）Pyrolyzing the paper towels-Fe（AC）₂-Co（AC）2 mixture precursor can obtain a novel porous carbon based hybrid catalyst.After optimizing the Fe（AC）2/Co（AC）2 ratios of paper towels-Fe（AC）2-Co（AC）2 mixture precursor,the resultant Fe0.5Co0.5-N/PCs sample own the typical 3D hierarchical meso/macroporous structures,large specific surface area,and vast carbon edges/defects.Moreover,large amounts of M-N-C、N-C and CoFe@C active sites are uniformly dispersed along the surfaces of Fe0.5Co0.5-N/PCs.In alkaline electrolyte,Fe0.5Co0.5-N/PCs shows considerable ORR activity comparable with commercial Pt/C catalyst via a 4 e-pathway.For OER catalysis,it also displays a more negative E10.（4）Pyrolyzing the mixture precursor of the hollow natural product catkin,Fe Cl₃ and melamine will realize the in-situ growth of iron and nitrogen co-doped carbon nanotubes（denoted as Fe/N/CNT）along with both inner and outer surfaces of PCFs.As the excellent electron transinformation rate,abundant mass transport channels and uniformly dispersed active sites（Fe-N-C,N-C and Fe@C）along the surfaces of Fe/N/CNT@PCF.The ORR catalyzed by Fe/N/CNT@PCF is efficient accompanying higher durability of ORR electrocatalytic activity and more excellent methanol tolerance compared with the commercial Pt/C catalyst.When the PCF matrices were used for loading CuO,vast bamboo leaf shaped CuO nanorods uniformly dispersed along with both inner and outer walls of PCFs.The novel CuO NR@PCFs demonstrates excellent oxidation and detection efficiency to glucose.（5）The homogeneous precursor solution [i.e.,PVA-Fe（C₂H₃O₂）₂-H₃PO₄] were first electrospunned into the typical 3D PVA/Fe（C2H3O2）2/H3PO4 precursor networks.In the carbonizing processes,H3PO4 works as both P sources and pore forming substance.Upon optimizing the dosages of H3PO4 in precursor slurries and the calcination temperatures,the resultant Fe/P/C0.5-800 networks own vast 3D hierarchical meso/macroporous structures,large specific surface area and vast carbon edges/defects.Above all,large amounts of Fe-P、P-C and Fe3C@C active sites are uniformly dispersed along the total surfaces of Fe/P/C0.5-800 networks.Furthermore,Fe/P/C0.5-800 networks display excellent catalysis activities anddurability for ORR/HER/OER catalysis.（6）The homogeneous PVP-Fe（AC）₂-Co（AC）₂-DMF precursor solution were first woven into the typical 3D networks consist of vast long fibers.Upon optimizing the Fe（AC）2/Co（AC）2 adopted in precursor slurries and the pyrolysis temperature,a novel 3D hierarchically meso/macroporous flower-like architecture of ultra-thin N-doped carbon nanosheets（NCNS）with fine FeCo@NC core-shell units dispersed on surfaces（denoted as FeCo@NC/NCNS）is successfully synthesized.Fe0.5Co0.5@NC/NCNS also owns abundant3 D hierarchical meso/macroporous structures,large specific surface area and vast carbon edges/defects.The surfaces of Fe0.5Co0.5@NC/NCNS also disperse large amounts of M-N-C and FeCo@NC active centers.More importantly,when Fe0.5Co0.5@NC/NCNS was used as the positive and negative electrodes in a two-electrode system for overall water splitting,it displays excellent catalysis activities accompanying the excellent catalysis long-term stability.