| It is crucial to develop high performance and stable non-precious metal oxygen reduction reaction catalysts for realizing the large-scale commercial use of fuel cells.The metal-porphyrin monomers with good chemical stability,high conjugate structure and good four electron reduction selectivity are ideal oxygen reduction reaction electrocatalysts,metal-porphyrin polymers have extended conjugated frameworks,which can exhibit better ORR electrocatalytic activity and catalyse ORR to follow the four electronic processes.The polymers of metal-porphyrin are usually synthesized by organic synthesis,but the method is more complicated and poor controllability,in this paper,simple and controllable electrochemical polymerization of metalloporphyrins have been achieved by electrochemical polymerization with simple operation and easy adjustment of polymerization parameters,at the same time,the metalloporphyrins polymers prepared by the method can be directly prepared on a conductive substrate and can be used as an electrochemical catalytic electrode to simplify the electrode preparation process.The functional groups of meso-tetra(4-aminophenyl)porphine(TAPP)and its metal derivatives are phenylamin,and the process of polymerization is similar to aniline polymerization,which tends to be polymerized,so we choose TAPP and its metal derivatives as research objects to carry out the following two aspects of the study:(1)Cyclic voltammetry was used to realize the electrochemical polymerization of TAPP monomer.TAPP polymer with the morphology of inerratic and integrated array structure was obtained by adjusting the solvent composition of the reaction solution,the scanning speed and the number of cycles of the cyclic voltammetry.Based on the conditions of cyclic voltammetry,the morphology of TAPP polymer was further optimized by adjusting different potentials and reaction time by potentiostatic method.The polymer was characterized by UV-vis absorption spectroscopy(UV-vis),infrared spectrum(IR spectrum)and the polymerisation mechanism was verified,besides,the ability for electrocatalyzing ORR of TAPP polymer was preliminary explored.Finally,we extended the electrical polymerization method to prepare FeTAPP and NiTAPP polymers.The UV-visible absorption spectroscopy test was used to prove that the FeTAPP monomer and the NiTAPP monomer were polymerized.Then we explored the effect of different scanning potential ranges and scanning cycles on the morphology and electrocatalysing ORR performance of the polymers.(2)TAPP,FeTAPP and NiTAPP were electrochemically polymerized onto the surface of Zn O surface with the ZnO arrays by cyclic voltammetry using template-assisted method,porphyrin polymers-ZnO composite nanorod arrays electrode were obtained.The physical structure was characterized by field emission scanning electron microscopy(FESEM),transmission potential microscopy(TEM)and UV-vis absorption spectroscopy(UV-vis).The result confirmed that the as-prepared material took on core-shell structure and the polymers were uniformly distributed on the surface of ZnO.Then the ZnO@pMTAPP(M = H,Fe,Ni)composites were calcined at argon atmosphere,the calcination temperatures was setted as 600 °C,700 °C and 800 °C,respectively.The material was heated for 2 h at the heating rate of 5 °C/min.The performance of electrocatalysing ORR was compared by cyclic voltammetry(CV)and linear sweep voltammetry(LSV),which was to explore the electron transfer in the process of catalysing oxygen reduction reaction,the material which showed best performance of catalysing oxygen reducing was conducted on the test of resistance to methanol poisoning,and then commercially available Pt catalysts were also compared.Finally,the stability of the catalyst was evaluated by the change of current density after 5000 s at-0.4 V(vs.Ag/AgCl)through i-t method.In addition,the porphyrin was polymerized on the carbon cloth surface and then calcined to test its catalysing oxygen reduction properties,compared with ZnO@pMTAPP-800 with array structure.to investigate the influence of array structure on the activity of oxygen reduction reaction. |
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