Preparation And Surface Modification Of Nitrogen-doped Carbon Nanotubes And Their Application In Gas Electrocatalysis

Nitrogen-doped carbon nanotubes are widely used in electrocatalysis and many other fields because of their abundant active sites,excellent electrical conductivity and convenience for batch preparation.Carbon dioxide reduction and hydrogenation reaction are both gas-consuming reactions,which requires that the material itself has not only good electrocatalytic activity,but also sufficient three-phase contact between the electrode,the reaction gas and the electrolyte.Meanwhile,taking both thermodynamics and kinetic factors into consideration could fully exploit the advantages of the material to achieve efficient electrocatalytic efficiency.Among the catalysts reported in the current literature related to carbon dioxide electrocatalytic reduction reaction,many materials have shortages such as large overpotential,low current density,or low Faraday efficiency.As for the hydrogenation reaction,although platinum is used as a highly efficient catalytic material due to its good hydrogenophilicity,its high cost still hinders further application.In view of these problems described above,and combined with the research status of carbon nanotubes in electrocatalysis,we further explored the properties of nitrogen-doped carbon nanotubes:1.Nitrogen-doped carbon nanotube arrays(NCNTs)were applied to the electrocatalytic reduction of carbon dioxide.NCNTs with uniform size and a large number of active sites were prepared by hydrothermal method and the following CVD method.The arrays electrode avoided the use of binders,reduced the resistance of electrodes and improved the utilization of electric energy.Reductive acid was used to improve the purity of carbon nanotubes.The addition of a polytetrafluoroethylene(PTFE)modified layer to prepare an underwater superaerophilic electrode greatly improves the kinetics of the electrode reaction.At-1.4V vs.Ag/AgCl,the carbon monoxide has a Faraday efficiency of 95.56%with high current density(4.56 mA cm-2)and stability.The nitrogen-doped carbon nanotubes prepared in the first step were further applied to the photothermal evaporation reaction,and good effects were still obtained.2.Study on platinum modified carbon nanotubes for electrocatalytic hydrogen oxidation.NCNTs embedded with cobalt metal were grown by methods similar to the previous one,then plated 2?5 nm trace platinum particles on the arrays by cyclic voltammetry.Although platinum loading of carbon nanotube arrays is less than a quarter of the commercial Pt/C,the current density(0.619 mA cm-2)are better than the contrast(0.485 mA cm-2).Furthermore,the modification with polytetrafluoroethylene improves the aerobic property,and the catalytic activity is greatly enhanced.Under 1.0 V vs RHE,the current density of PTFE 0.4-Ptl-H-CoNCNTs can reach up to 17 mA cm-2.