Preparation And Catalytic Performances Of Metal And Nitrogen Co-doped Carbon Materials

The deterioration of water quality brings great difficulties to human beings in the term of of drinking water.Catalytic chemical processes are important to solve the problem of water environment pollution.The catalyst is an essential cornerstone in the catalytic processes.Meanwhile,rapid consumption of fossil energy is causing a global energy shortage,forceing people to develop new energy resources.As a type of important new energy,the development of fuel cell is inseparable from the efficient electrocatalyst.Therefore,the catalysts are an important class of substances needed for sustainable development in both environment and energy fields.The metal and nitrogen co-doped carbon（M-N-C）composite is composed of metal species coordinated on the nitrogen doped carbon skeleton,which are well-positioned to exploit more active sites.M-N-C catalysts show excellent catalytic activities in the above-mentioned application of the degradation and electrocatalysis.Herein,we fabricate a efficient M-N-C catalysts which Cu and Co metals are anchored and coordinated on the carbon matrix framework,respectively.The main research results are as follows.（1）A Cu and N co-doped graphene composite（Cu/N-rGO）was fabricated via a hydrothermal method（180 ^oC,6h）using the oxide graphene,copper nitrate trihydrate and ammonia as raw materials.The enhancement effect of graphene by Cu and N co-doping on the catalytic activation of H₂O₂ are studied.The effects of various reaction parameters（Cu load,H₂O₂ concentration,Na₂CO₃ concentration,and temperature）toward the adsorption and oxidative degradation of Rh B over Cu/N-r G are investigated.It is found that,by the as-obtained Cu/N-rGO at 3wt%of Cu-feeding mass as the catalyst with addition of 40mmol L^-1H₂O₂ and 4 mmol L^-1 Na₂CO₃,the Fenton-like process removed more than 94%of the added Rh B(30 mg L^-1)in 20 min.Quenching experiments and EPR analysis demonstrated that the major reactive species generated in the catalytic process were surface-bound·OH.Horeover,Cu/N-rGO also showed good has excellent electrochemical catalytic performances through the four-electron mechanism.On the Cu/N-rGO electrode,the ORR reaction exhibited a low onset potential of-0.1 V and half-wave potentials of-0.248 V,being close to that of Pt/C electrode.The 3%Cu/N-rGO catalyst still retained 97.5%of its original current after 1000s in methanol,whereas the 20%Pt/C displayed an dramatically decline（current loss of 23.9%）,illustrating the superior tolerance toward methanol of 3%Cu/N-rGO relative to that of 20%Pt/C.Such outstanding catalytic properties were attributed to the abundant active sites of Cu-N-C.（2）A novel MF-Co carbon composite,which was rich in both Co O and Co N species,was prepared through a simple pyrolysis process(5 ^oC min^-1,400^oC,2h)using the bulk Melamine foam（MF）,cobalt nitrate hexahydrate as Co source;Its catalytic reduction performance was also studied.The MF rich in nitrogen,and build a 3D interconnected network-like N-doped carbon framework after carbonization,which support and disperse the metal catalysts species.3D pore provides convenient mass transfer channels,and improves mass transfer efficiency.After pyrolysis,Co-ions are effectively adsorbed and coordinated on the carbonized sponge surface,which obtains both Co O and Co N active species.We investigate the catalytic performance of the MF-Co catalysts by the reduction of p-NP in the presence of Na BH₄ and the effects of the preparation conditions（the Co（NO₃）₂·6H₂O feeding amounts）and various reaction parameters including Na BH₄concentration and temperature.It was observed that the use of 1.3 mg L^-1 MF-Co catalyst together with 0.04 mol L^-1 Na BH₄ almost completely reduced the added of p-NP(0.2 mmol L^-1)in 7 min at 30 ^oC and the good reusability with nearly 100%of catalytic reduction efficiency after five cycles.In addition,it was found that MF-Co catalyst also has good reduction ability for other nitroaromatic compounds,and the reduction rate constant follows the orde of 4-NP>4-NT>2-NP>2,4-DNP>2,4,6-TNP.