Preparation Of Hetero-atoms Doped Carbon Nanofibers And Their Electrocatalytic Performance For Oxygen Reduction Reaction

As an energy device of conservation and conversion,fuel cells（FC）have many advantages,such as high energy density and efficiency,environmentally-friendly,which are considered to have a wide application in advanced energy field in the future.However,the sluggish kinetics of cathodic oxygen reduction reaction（ORR）limit the work efficiency of fuel cells seriously,and hinder the development of fuel cells in commercial application.Generally,using catalysts in cathode can accelerate the oxygen reduction reaction.Pt-based catalysts are considered to be the best ORR catalyst in the market currently,but they have no developed very well because of the scarcity and high-cost.In order to solve these problems,exploring other cathodic catalysts with low cost and high performances is necessary.In this paper,bacterial cellulose（BC）was used as carbon source to prepare carbon nanofibers（CNFs）composites toward ORR by the facile strategy.The as-prepared catalysts were tested by physical characterizations and electrochemical measurements,some results were presented as follows:（1）BC was used as the carbon source,ferric chloride as the iron source and phosphoric acid as the phosphorus source to synthesize the Fe-P/CNFs by impregnation method and pyrolyzation.From the SEM and TEM images,we found that the Fe-P/CNFs inherited the 3-dimentional（3D）network structure of BC which was beneficial to the diffusion of oxygen and electrolyte permeating in ORR.The P-C,Fe-O-P in Fe-P/CNFs by the XPS analysis was the active site which played an important role for enhancing ORR.（2）Based on the 3D network structure of BC,the BC was used as template.Polydopamine was coated on the surface of BC by in-situ polymerization,preparing the N-CNFs.And then we employed a facile chemical reduction method to attach Au nanoparticles on the N-CNFs to obtain the Au-N/CNFs.Au-N/CNFs displayed the high ORR performances and the better stability because of the efficient ORR catalytic activity and steady electron structure of Au nanoparticles.（3）BC was used as substrate,then introducing melamine and cobalt nitrate to preparethe Co-N/CNFs via pyrolysis.The electrochenmical measurements have confirmed the best carbonization temperature and the introduction of Co²⁺ during the preparation of Co-N/CNFs.XPS data demonstrated that the cobalt could increase the content of nitrogen,and the formations of Co-N,Co@CoO active sites in Co-N/CNFs were the key to enhance ORR.