Application Of Molecular Catalysts Metalloporphyrin In The Cathode Catalyst Layer Of Fuel Cells

Fuel cells are one of the most potential and promising technologies currently available for power generation and heat supply.It can be used in a very wide range of application scenarios,showing good development prospect.However,in order to make this technology feasible for commercialization,there are still some limitations that must be overcome first.Taking proton exchange membrane fuel cells(PEMFCs)as an example,in PEMFCs,the performance of the cathode catalyst layer depends on the effective formation and uniform distribution of the three-phase boundaries(TPBs).However,the traditional cathode catalyst layer structure based on heterogeneous catalysis exhibits low catalyst utilization and mass transfer efficiency of oxygen reduction reactions(ORR),further restricting the development of PEMFCs.Therefore,we covalently grafted ORR molecular catalyst TMPPFe onto the side chain of Nafion ionomer,which enabled the catalytic center of the transition metal macrocyclic to be anchored within the ionic channel.This unique structure may mimic a homogeneous catalytic environment,which enables complete utilization of catalytic centers and substantially improves the mass transfer efficiency.Mossbauer spectroscopy analysis showed that the kinetics of electrode reaction was improved due to the increase of electron density around the Fe center.In addition,improvements in the utilization of catalytic active sites and mass(proton,oxygen)transfer effectively promoted the performance output of fuel cells.In order to improve the stability and performance of MMCs in the catalyst layer,MMCs is further considered for use in anion exchange membrane fuel cells(AEMFCs),Based on the above research,herein,the ORR molecular catalyst TFPPCo was in-situ copolymerized onto carbon nanotubes with small molecular materials that can be quaternized,which was subsequently quaternized to obtain a composite material.A uniform distribution between the catalytic centers of the composite material and the ionic channels composed of quaternary ammonium salts was achieved at the molecular level.The results indicate that the coordination and electronic structure of the catalytic center had not changed,the intrinsic catalytic activity of the catalytic center had not improved,however,there is a significant improvement of the fuel cell performance,which is due to the improvement of the utilization of catalytic sites and the conductivity of composite materials.Based on the research in the above two chapters,Based on the research in the above two chapters,after applying MMCs to the AEMFCs cathode catalyst layer and achieving satisfactory performance,the performance of MMCs in microbial fuel cells(MFCs)under neutral media was preliminarily explored,compared to H2/O2 fuel cells,MFCs has milder conditions and is more friendly to catalysts.The Metal Organic Frameworks(MOFs)material has a well-defined structure and it is easy to adjust,and it has large specific surface area and permanent porosity,which can promote gas transfer.Additionally,the immobilization and accumulation of redox active sites of the MOFs material can be controlled to realize an ideal density for improved ORR reaction kinetics.Therefore,a MOFs material for MFCs under neutral media was designed and prepared.Similar to the research results in the previous two chapters,composite materials containing quaternary ammonium salts and carbon nanotubes showed good catalytic activity under neutral conditions and achieved good performance output on MFCs cathodes.The novel catalyst layer structure designed and prepared in this thesis can provide a new platform for the development of high-performance molecular catalysts for fuel cells and other energy devices,pointing out a direction for the development of fuel cell technology,and providing new insights for the large-scale commercial application of fuel cells.