POMs Or MOFs Based Composite Electrocatalysts Prepared By Electrospinning

In recent years,it is urgent to develop alternative,clean,efficient,and renewable energy sources,due to the increasingly severe energy crisis,environmental pollution,and global warming.Fuel cell as a new energy have been intensively researched,however,rare and noble Pt-based catalysts have limited its widespread application,and the transition metal compounds are widely studied with highly similar Pt metal.In this paper,a series of transition metal based composites were designed and synthesized using transition metal-rich POMs and MOFs as precursors,and the electrochemical oxygen reduction performance was studied.The main work includes the following three aspects:?1?PMo₁₂@PAN/PMMA fibers was prepared by electrospinning using phosphomolybdic acid(H₃PMo₁₂O₄₀.xH₂O,PMo₁₂)as precursors,and MoS₂ wrapped in nitrogen-doped porous carbon fiber?MoS₂@N-PCFs?were obtained by sulfuration under N₂ atmosphere.In addition,by adjusting the PAN/PMMA mass ratio and vulcanization temperature,MoS₂@N-PCF-2 exhibited the best ORR performance when the mass ratio of PAN/PMMA was 1:1 and the vulcanization temperature were 800?.?2?NENU-5@PAN/PMMA fiber was prepared by electrospinning using NENU-5 as precursors,and Cu_1.96S/Cu₉S₅/MoS₂ coated in nitrogen-doped porous carbon fiber (Cu_1.96S/Cu₉S₅/MoS₂@N-PCFs)was obtained by sulfuration in nitrogen atmosphere.At the same time,by comparing Cu_1.96S/Cu₉S₅@N-PCFs,MoS₂@N-PCFs,and Cu_1.96S/Cu₉S₅/MoS₂,prepared from different precursors,the influence of different components of the catalyst and 1D fiber structure on ORR performance were investigaed.In addition,the effect of different vulcanization temperatures on the ORR electrocatalytic properties of Cu_1.96S/Cu₉S₅/MoS₂@N-PCFs was also investigated.The results show that Cu_1.96S/Cu₉S₅/MoS₂@N-PCFs-2 obtained by vulcanized at 800? exhibited the best ORR activity,which was superior to those obtained at 700? and 900?,and superior to the other three catalysts.More importantly,the excellent ORR performance of Cu_1.96S/Cu₉S₅/MoS₂@N-PCFs-2 is the synergistic effects of Cu_1.96S/Cu₉S₅,MoS₂ and nitrogen-doped porous carbon fibers.?3?Zn_xCo_1-x-ZIFs@PAN fibers were prepared by electrospinning using Zn_xCo_1-x-ZIFs as precursors,and uniform Co nanoparticles encapsulated in nitrogen-doped porous carbon fibers?Co@N-PCFs for brevity?were obtained by directly carbonized.Herein,with precisely controlling of the Zn/Co molar ratio in the Zn_xCo_1-x-ZIFs precursor and carbonization temperature,Co@N-PCF-3 exhibited excellent ORR activity.The half wave potential,limiting current,stability and methanol resistance of Co@N-PCF-3 were superior to commercial Pt/C,except the onset potential.Through a series of characterizations such as XRD,TEM,N₂-adsorption/desorption measurements,Raman,and XPS,it was found that the excellent ORR performance of Co@N-PCF-3 is the collaborative role of the following aspects:the mesoporous texture,1D fibrous structure,larger specific surface area,high graphitization degree,abundant active sites derived from Co-N_x and the higher content of graphitic-N and pyridinic-N and superior electron and mass conductivity.