Study On Preparation And Electrocatalytic Performance Of Transition Metal-Based Nitrogen-Doped Carbon Composite

Hydrogen is a broad application prospects energy with high efficiency,environmental protection.Low temperature fuel cell is a new type of energy storage and conversion device,which can be widely used in communications,aerospace,portable power,transportation and other fields.In this paper,the design uses transition metals nickel,cobalt,iron,copper(Ni,Co,Fe,Cu)and nitrogen-doped carbon materials to composite,with the help of the synergy between nitrogen-doped carbon materials and transition metals to obtain a new type of high efficiency through high-temperature heat treatment.The transition metal-based nitrogen-doped carbon electrocatalyst and its application in the study of oxygen reduction reaction(ORR)in fuel cells and hydrogen evolution reaction(HER)in the process of electrolysis of water are as follows:1.Nitrogen-doped carbon nanotubes(N-CNTs/E-NNP)with nickel-based nanoparticles embedded on the top were successfully synthesized by direct calcination of melamine and nickel foam in argon using an in-situ one-step calcination strategy.At 520°C and 540?,the melamine pyrolysis derivative interacts with the unevenly mixed nickel foam to form nickel-based nanoparticles.After heating to 700°C,the formed Ni-based nanoparticles promoted the formation of N-CNTs.The ORR test of the material shows that the initial potential(E_onset)and half-wave potential(E_1/2)in 0.1 M KOH are 0.96 V and 0.86 V(vs.RHE),respectively,which are comparable to commercial 10 wt%Pt/C Similar potential.However,N-CNTs/E-NNPs have higher stability and better methanol tolerance.In addition,the Tafel slope of N-CNTs/E-NNP is 76 m V dec^-1lower than 83m V dec^-1of commercial 10 wt%Pt/C,showing a good kinetic process.The distribution of transition metal nanoparticles on N-CNTs will affect the ORR activity of CNTs.Compared with transition metal-based nanoparticles loaded on the outer surface of N-CNTs,transition metal-based nanoparticles encapsulated in N-CNTs can induce host-guest electronic interactions,weaken the Oswald-like effect,and improve the performance of CNTs.The local work function makes the outer surface of the carbon layer have higher ORR activity and stability.The simple preparation,low cost,and superior catalytic performance make it a new path for the development of ORR catalysts.2.Firstly,copper and cobalt are uniformly grown on the surface of nickel foam through hydrothermal reaction to form Cu-Co-Ni-based ternary nanoparticles(T-CCN),and then melamine and T-CCN are successfully calcined through direct program in argon.Nitrogen-doped carbon nanotubes(N-CNTs/T-CCN)embedded with copper,cobalt,and nickel-based nanoparticles on the top were synthesized.The starting potential and half-wave potential in0.1 M KOH are 0.96 V and 0.87 V(vs.RHE).Most importantly,compared with 20wt%Pt/C,the catalyst showed better methanol tolerance and higher stability.The H₂O₂output is less than 7.5%,and the electron transfer number(n)is about 3.9.Compared with the metal-based nanoparticles supported on carbon,the nano-particles of the transition metal wrapped by the carbon material attenuate the Oswald-like effect in the material.The Fermi level of metal is lower than that of CNTs.When the metal and carbon materials are in contact,the buffer layer formed can allow electrons to flow from the metal to the CNTs to maintain work balance.At the same time,for nanomaterials,the periodic boundary is destroyed,the atomic density of the surface layer of the nanoparticle is reduced,and the locality and coherence are enhanced to make the distribution of transition metals uniform and enhance the surface activity of the nanomaterial.Good electron and mass transfer and synergy make N-CNTs/T-CCN show excellent ORR catalytic activity.3.Electrodeposit aniline on carbon paper(CP)by galvanostatic deposition method to obtain vertically aligned PANI.Then,using organic matter as the skeleton and Fe and Co as the connection point,PANI coated with MOFs-74 was prepared by the hydrothermal reaction of PANI with Fe Cl₂and Co(NO₃)₂.Then N-C@Co P₃/Fe P is obtained by phosphating.Among them,the vertically arranged PANI has many amino groups as fixed points of metal ions,which can prevent the aggregation of metal nanoparticles,thereby driving the heterogeneous nucleation and growth of MOFs.After phosphating,electrons tend to transfer from metal atoms to more negatively charged phosphorus atoms.Phosphorus atoms can effectively capture protons.The structure of MOFs can provide more active sites and unimpeded transmission channels for electrons,which can give full play to the synergy of materials.In the 0.5 M H₂SO₄electrolyte,the initial overpotential of N-C@Co P₃/Fe P is only 50.04 m V,and the Tafel slope and impedance are low.In addition,the catalyst also has excellent durability,and the current density remains 96.3%after 6 hours.The vertically arranged conductive PANI nano-array obtained by electrodeposition retains the morphology of the array to the greatest extent,thereby realizing the formation of the array morphology of the catalyst surface and the construction of the nitrogen-doped carbon matrix.The obtained N-C@Co P₃/Fe P has excellent electrocatalytic performance.This research will open up ideas for a new generation of electrocatalysts with porous hybrid nanostructures,and have broad prospects in controlling morphology and function and potential applications in other technical systems.