Heteroatoms Doped Porous Carbon Catalysts For ORR

The fast development of world economy demands a larger amount of energy supply than ever before.Meanwhile,the fossil fuel still takes an absolute portion in the energy component and causes a series of social and environmental problems.To put an end to the limitless energy crisis and environment pollution,and to seek for the sustainable development of human society,it is very much necessary to use large-scale new types of clean energy.Among them,the oxygen reduction reaction(ORR)is the key reaction in the energy conversion and storage devices as fuel cells and metal-air batteries.However the sluggish kinetics of the ORR in the cathode has greatly limited the efficiency of fuel cells and metal-air batteries.Noble metal(Pt)based catalysts is the state of art commercialized catalysts.Despite of the excellent efficiency,the noble metal(Pt)based catalysts suffer from several drawbacks such as high cost,scarcity and poor long-term durability.These drawbacks greatly hindered the application of noble metal(Pt)based catalysts.To develop cheap,highly efficient and stable catalysts based on non-precious metal or even metal free materials is the key to push on the real application of fuel cells.Here,we have prepared a series of nonprecious metal based catalysts and metal free catalysts through doping,assembling and template,the main achievement were shown down below:1.It still remains a great challenge to rationally design the nonprecious metal electrocatalysts to replace precious Pt catalysts in fuel cells.Here,we propose a core/shell nanoparticle(NP)template strategy to synthesize nonprecious metal and nitrogen-codoped porous carbons as efficient bifunctional electrocatalysts for oxygen reduction reaction(ORR)and oxygen evolution reaction(OER).As a typical sample of the strategy,we use a ZnO@ZIF-67 core/shell NP as a self-sacrificed template and mix with additional nitrogen/carbon sources to synthesize Co,N co-doped porous carbons.The resulting Co/N-codoped electrocatalysts not only show almost similar ORR activity with commercial 20%Pt/C,but also exhibit comparable OER activity with IrO2 in alkaline medium.Moreover,we also use density functional theory to investigate ORR/OER mechanism of Co/N-codoped porous carbons,and further reveal that the highly efficient electrocatalysts can be designed by using N-doped carbons to encapsulate electrophilic components like Co3O4,which provides a new strategy for development of bifunctional catalysts for ORR and OER.2.We use the composite of inexpensive polyaniline and superfine polytetra-fluoroethylene powder as precursor to synthesize a metal-free N,F-codoped porous carbon catalyst(N,F-Carbon).Results indicate that the N,F-Carbon catalyst obtained at the optimized temperature 1000?exhibits almost the same onset(0.97 V vs.RHE)and half-wave potential(0.84 V vs.RHE)and better durability and higher crossover resistance in alkaline medium compared to commercial 20%Pt/C,which is attributed to the well dispersion of fluorine and nitrogen atoms in the carbon matrix,high specific surface area and the synergistic effects of fluorine and nitrogen on the polarization of adjacent carbon atoms.This work provides a new strategy for in situ synthesis of N,F-codoped porous carbon as high efficient metal-free electrocatalyst for ORR in fuel cells.3.We use thiourea and polytetrafluoroethylen(PTFE)superfine powder as precursor to prepare a series metal-free N,F,S-tridoped catalysts.In alkaline medium,the catalyst obtained at the optimized temperature 1000?,SNFC-1000,shows a onset potential(0.97 V vs.RHE),half-wave potential(0.86 V vs.RHE)and the same limited current density with commercial 20%Pt/C catalyst at the same catalyst loading.Moveover,SNFC-1000 has better durability and higher crossover resistance.We believe the highly efficient activity is attributed to the successful doping of N,F and S into the carbon bones,which leads to synergistic effects of the doped heteroatoms.This work provides a new strategy for in situ synthesis of heteroatoms doped porous carbon as high efficient metal-free electrocatalyst for ORR in fuel cells.