Preparation Of Lipstick-type Hollow Mesoporous Nitrogen-doped Carbon Materials And Their Research On Their Oxygen Reduction Activity

The rapid changes in social life are inseparable from the great contribution of energy.However,the increasingly severe environmental crisis and the depletion of non-renewable energy sources have become problems that people have to face and need to be resolved.Therefore,it is urgent to explore and develop renewable,effective,safe,and environmentally friendly new energy sources and technologies.Because of its advantages,fuel cell has entered the field of vision and become a hot field of new energy research.The oxygen reduction reaction(ORR)of the cathode has become the main limiting factor for the development of fuel cells due to its extremely slow kinetic process.A supported catalyst is the best way to solve this problem.To date,platinum(Pt)and its composites are the most excellent catalysts for ORR catalysis.But Pt's low abundance and high cost have greatly limited its wide application.Based on this,non-precious metal catalysts have aroused great interest.Among them,non-metal lic carbon-based catalysts have been widely concerned because of their low cost,wide sources,strong stability,and good resistance to acids/bases/methanol.But because the original carbon material is chemically inert and has poor catalytic activity,it must be modified to improve its electrocatalytic performance.In this research,we adopt a bottom-up template participation strategy and prepare a series of lipstick-like hollow mesoporous nitrogen-doped carbon(HNC-1000)materials through solvothermal reactions and other methods.Methods such as thermal reflux and solvothermal reaction,as well as the effects of reaction temperature,reaction time,and raw material ratio on the structure and morphology of ZnO particles,ZnO@ZIF-8 core-shell particles,and the target catalyst HNC-1000 were investigated.The results of field emission scanning electron microscopy and transmission electron microscopy show that the precursor ZnO particles,the intermediate ZnO@ZIF-8 core-shell particles,and the target HNC-1000 particles all maintain a lipstick-like morphology,and HNC-1000 is a hollow nitrogen carbon material.The specific surface area and pore size analysis show that the synthesized HNC-1000 has a very rich mesoporous structure and belongs to a mesoporous material.X-ray photoelectron spectroscopy results showethat the nitrogen in the catalyst HNC-1000 is mainly pyridine nitrogen and graphite nitrogen.Compared with the structure of NC-1000 prepared with ZIF-8 as a precursor without template,it is shown that the lipstick-like hollow morphology and mesoporous structure of HNC-1000 are due to the influence of the template and the preparation method.In terms of ORR activity,the prepared HNC-1000 has excellent catalytic performance:the onset potential(E0)and the half-wave potential(E1/2)are 0.98 V and 0.85 V,respectively,and the limiting diffusion current density JLis 5.51 mA cm-2.The performance of HNC-1000 is very close to the commercial Pt/C(20 wt.%),much higher than the NC-1000 catalyst prepared by the template-free method.At the same time,HNC-1000 also has high stability and excellent methanol tolerance,which is superior to commercial Pt/C catalysts.The excellent performance of HNC-1000is closely related to its unique morphology and composition.