| With the continuous consumption of non–renewable fossil energy and the accompanying environmental pollution problem,the search for clean and renewable energy has become a hotspot to meet the current rapid development of society.As a clean energy conversion system,electrochemical energy conversion has the characteristic of mutual conversion between electrical energy and chemical energy,this advantage can contribute to the needs of current sustainable energy.In order to design and develop efficient energy conversion system,the construction of cost–effectiveness non–precious catalyst with excellent catalytic performance is the key.Although some non–noble metal–based catalysts have catalytic performances that even exceed those of precious metals,they still can not meet the present huge challenges.Carbon–based composite materials,due to their unique physical and chemical characteristics of controllable morphology and controllable microstructure,have become the key research objects of electrochemical energy conversion.Carbon–based composite materials have demonstrated excellent electrochemical conversion efficiency.This article focuses on the design,preparation and application of non–noble transition metal carbon–based composite materials in the field of electrocatalytic energy conversion.Some results were obtained as followed:?1?An iron–nickel bimetallic phosphide nanoparticle supported on three–dimensional porous carbon?FexNi2–xP/PC??0<x<2?was prepared by co–deposition method and in–situ phosphating method.The large specific surface area,rich micropores and oxygen–containing functional groups ofthe porous carbon substrate,contribute to the pre–dispersion of Fe Ni–OH precursor on the carbon sheet through confined growth,and the ultra–small FexNi2–xP nanoparticles supported on interconnected porous carbon sheets were obtained after the phosphating process.The FexNi2–xP/PC catalyst has a large specific surface area and high conductivity,which can provide abundant catalytic active sites,can optimize the electronic structure,facilitate mass transfer,and improve electrocatalytic activity.By adjusting the Ni/Fe source ratio,the optimal bimetallic phosphide exhibited an ultra–small overpotential of 210 m V at10 m A cm–2 for the oxygen evolution reaction in alkaline electrolysis cell.When the catalyst was used as the cathode and anode materials for water splitting in alkaline electrolyte,the overpotential of 1.63 V at 10 m A cm–2 was obtained.?2?Through a simple organometallic framework?MOF?assisted strategy,and the pyrolysis of MOF and DCA mixed powder,we successfully designed and synthesized a metal–Nx component/N–doped carbon nanotube–coated Co Ni alloy nanoparticles composite?Co Ni@NCNTs?.The high conductivity of the carbon nanotubes in the composite,the abundant M–Nx sites,the synergy of N–doped carbon nanotubes and monoatomic Co/Ni–Nx sites,and the optimized electronic structure make it highly efficient dual–function catalytic activity and durability.Specifically,in alkaline electrolytes,the catalyst exhibits excellent OER and ORR performance.The overpotential at a current density of 10 m A cm–2 is only 370 m V for OER,and the half–wave potential is 0.822 V for ORR.The voltage interval between OER and ORR is only0.78 V.This work can open up new perspectives for the design of bifunctional electrocatalysts.?3?Through the dual action of small molecule confinement and carbon pores,Fe?phen?3 complex and porous carbon precursor were calcined at high temperature to synthesize an atomically dispersed Fe atom anchored in porous carbon nanocomposites?Fe–SA/PC?.The study found that the optimized Fe–SA/PC catalyst has excellent electrocatalytic performance for ORR with the half–wave potential of 0.91 V,and high catalytic stability and methanol resistance.Experimental and theoretical studies have proved that the vacant edges with oxygen can promote the micropores to capture Fe?phen?3 complex in advance,and the double–limiting action can inhibit the aggregation of iron during the pyrolysis process,thereby forming a uniformly dispersed Fe–Nx components.In addition,compared with the complete Fe–Nx atomic configuration,Fe–Nx sites with adjacent carbon defects can effectively reduce the catalytic reaction barriers.This work can provide new strategies for designing and constructing high–performance single–atom catalysts.?4?Through double solvent method,transition metal ions pre–dispersed into ZIF8channels were prepared.Based on the channels and the nitrogen–rich organic framework,a variety of M–Nx–C composites were synthesized under the condition of high temperature pyrolysis duo to space confinement and nitrogen capture.This type of M–Nx–C composite catalyst can exhibit excellent electrocatalytic ORR activity.Among them,the catalyst with Mn–Nx component dispersed on the graphite carbon skeleton generated by carbonization of the structure shows excellent ORR electrocatalytic performance in both acidic and alkaline media.Specifically,the half–wave potentials of Mn–Nx–C catalyst in 0.1 M KOH and 0.5 M H2SO4 are 0.9 V and0.76 V,respectively.Compared with commercial Pt/C catalysts,Mn–Nx–C catalysts have good ORR activity.Such methods can be extended to prepare a variety of other single–atom composite catalytic materials,and provide novel ideas for the design and preparation of single–atom embedded carbon–based composite materials. |
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