Construction Of Hollow Porous Carbon Sphere@cobalt Phosphide/nitrogen Doped Carbon Supported Platinum Hybrid Catalyst And Its Application In Methanol Fuel Cell

With the emergence of energy and environmental issues,demand for sustainable energy is growing.In recent years,fuel cells have attracted attention of scientists for their high conversion efficiency.Among them,direct methanol fuel cells（DMFCs）are easy to store with high power density and energy density,they also can be started quickly at low temperatures.However,Pt-based catalysts are still the most effective catalysts for DMFCs,the high cost of Pt-based catalysts and decrease in activity due to adsorption of carbon-containing intermediates have hindered their commercial development.To address these issues,researchers are looking for efficient cocatalysts in which transition metal phosphides are widely recognized for their unique electronic and catalytic properties.In this paper,ZIF-67 is used as a direct source of phosphide.But the low carbon content of the MOFs leads to poor conductivity,it is assembled on the surface of the phenolic resin in this subject,so that the carbonized composite materials will exert their respective advantages.On the one hand,the hollow porous carbon sphere obtained by carbonization of the phenolic resin has good electrical conductivity and low electrical resistance.On the other hand,ZIF-67 can directly convert to CoP/NC by carbonization and phosphating.In this paper,hollow porous phenolic resin spheres（HPCS）were prepared by in-situ polymerization using nano silica spheres as templates.Then,ZIF-67 was assembled on the surface of the hollow porous phenolic resin,followed by carbonization and low-temperature phosphating to obtain hollow porous carbon spheres@CoP/nitrogen-doped carbon（HPCS@CoP/NC）.Finally,Pt-HPCS@CoP/NC catalyst was prepared by microwave-assisted polyol.Field emission scanning electron microscopy（FE-SEM）,X-ray diffraction（XRD）,X-ray photoelectron spectroscopy（XPS）,high-resolution transmission electron microscopy（HRTEM）and nitrogen adsorption-desorption isotherms were characterized to analyse characterization and structure,cyclic voltammetry（CV）,electrochemical impedance spectroscopy（EIS）,CO stripping voltammetry and chronoamperometry（I-t）was used to test the electrochemical performance of the catalyst.The results are as follows:（1）The diameter of the hollow porous phenolic resin is about 900 nm,the pore volume is 0.017 cm³ g^-1,the specific surface area is 6.082 m²g^-1.The obtained HPCS@CoP/NC composite has a hollow spherical structure with a pore diameter of 4nm with large specific surface area and pore volume,which can provide a large number of active sites,while the mesopores contribute to the transport of mass and electrons.TEM results show that the particle size of Pt nanoparticles is 2 nm,which is uniformly distributed on the HPCS@CoP/NC support,which is beneficial to the exposure of Pt active sites.XPS results confirmed a strong interaction between Pt and CoP,which exhibits an enhanced effect for the performance of the catalyst.（2）In order to determine the ratio of HPCS to ZIF-67,we prepared different Pt-HPCS@CoP/NC catalysts.The results show that the performance of the catalyst with250 mg HPCS is best.Electrochemical results show that the electrochemical specific surface area（ECSA）of Pt-HPCS@CoP/NC catalyst is 145.5 m²g^-1,the mass specific activity can reach 688 mA mg_Pt^-1,it also exhibits better stability and anti-CO ability.Therefore,the Pt-HPCS@CoP/NC catalyst is a promising anode catalyst for methanol oxidation reaction（MOR）of DMFCs.