Synthesis Of 2D Nitrogen-doped Mesoporous Carbon Catalyst And The Electrocatalytic Investigation On Oxygen Reduction Reaction

Traditional platinum-based catalysts show high electrocatalytic performance;however,its source scarcity and high price seriously hinder the wide application of fuel cells.Therefore,great efforts have been devoted to exploring alternative non-precious metal electrocatalysts with higher activity and lower cost.As for the nanostructured heteroatom-doped carbon,the precise control over the surface composition,like by nitrogen-doping,can effectively tune the chemical nature of the active site and thus increase the ORR turnover frequency.As known,apart from the catalysis itself,the mass transfer is of great importance in terms of the concentration polarization and the utilization efficiency of the active sites.Two dimensional(2D)nanostructure materials have attracted enormous attentions,because of its high specific surface area,a lot of exposure of active site and the regulation of mesoporous.Among them,2D nitrogen-doped carbon is an ideal candidate as an electrocatalyst for the ORR due to its unique features.In this work,nitrogen-doped mesoporous carbon(NMC)is synthesized by the nanocasting method.Then,the effect of co-template,the concentration of co-template and surfactant are extensively investigated on the NMC.Moreover,the microstructure,elemental composition and dimensionality are extensively investigated by the nitrogen ad/desorption isotherm,small angle X-ray diffraction,transmission electron microscopy,atomic force microscope,X-ray photoelectron spectroscopy.And electrochemical methods,including the cyclic voltammetry,rotating disk electrode,are applied to investigate the electrochemical behavior.Firstly,a novel ultrathin silica film with fingerprint-like mesopores is synthesized with the aid of the dual templates of graphene oxide(GO)and tri-block copolymer P123.The formation is proposed to proceed by a co-operative assembly mechanism.The paraller mesochannels originate from the template P123 micelles,meanwhile,the 2D morphology results from the cotemplate GO,which provides guidance for controllable morphology of mesoporous materials.Secondly,an ultrathin(thickness 1.0 nm)2D nitrogen-doped hierarchically porous carbon film(2DNHPC)is developed by introducing the GO.Characterizations reveal that 2DNHPC is featured by an extremely high aspect ratio(several hundred)and a bimodal pore distribution.Such a 2D hierarchically porous structure is found to facilitate both the mass transfer of the reactive species and the utilization of active site in the electrode.Thirdly,we employ another tri-block copolymer,F127,to further control the textural features of the 2D silica film.It is found that the parallel porous will be obtained when P123 is used as template;and when F127 is used,the vertical one will be obtained.Then,the silica is used as a template to direct the synthesis of the 2D nitrogen-doped mesoporous carbon,which yields a much better electrocatalytic activity than its Pt counterpart.Finally,introducing the cationic surfactant CTAB as template,the electrostatic interaction between ammonium cations and negatively charged GO will be effective in guiding the ordered mesoporous structure.Following this understanding,an ultrathin mesoporous silica film is synthesized here by the aid of dual templates,viz.GO and CTAB,which is then used as a template to synthesize nitrogen-doped mesoporous carbon(NMC)sheet.Analyzing its component and structure,a conclusion is drawn that its outstanding activity originates from the high nitrogen content,specific area and utilization of active site.