Synthesis Of Iron-based Nanomaterials And Application In Electrocatalytic Reduction Reactions

Nowadays,the extensive use of fossil fuels has resulted in severe environmental pollution.Hydrogen is regarded as the most promising clean and sustainable energy due to the zero-carbon emission and high energy conversion efficiency.Water-splitting performs as an efficient way to acquire hydrogen through the half-reaction of hydrogen evolution reaction（HER）.Up to now,platinum group metals（PGM）are still the most effective catalyst for HER and oxygen reduction reaction（ORR）.However,the high cost and scarcity of PGM catalysts impede their large-scale production and utilization.Thus,it is of vital importance to design efficient non-noble metal catalysts to overcome these limitations.Herein,this thesis mainly focuses on the design synthesis of low-cost iron-based nanomaterials and the investigation of their potential electrocatalytic HER and ORR activity.This thesis includes three parts in contents as follow:1.The design synthesis of hollow structured Fe₃O₄-Fe₃C-FeP/XC-72（Fe-C-P）nanocomposites through the solvothermal-calcination approach for HER catalysis.The unique hollow structure not only increases the surface area,which enables more exposed active sites but also enhances the mass transfer in the electrocatalysis process.In 1.0 M KOH,the overpotential of Fe-C-P is 180 mV at a current density of 10 mA cm^-2(denoted as 180 mV@10 mA cm^-2)and 470 mV to aquire a current density of 1000 mA cm^-2 for HER.In 1.0 M HClO₄,the HER overpotential of Fe-C-P is 144 mV@10 mA cm^-2,and320 mV@500 mA cm^-2,superior to the benchmarks without hollow structures.2.The design synthesis of nitrogen-doped mesoporous carbon spheres（meso-N-C）supported Fe₃O₄ nanoparticles through a micro-emulsion method and subsequent in-situ loading strategy for efficient ORR catalysis.Uniform Fe₃O₄ nanoparticles with a size of8.9±0.8 nm were well-dispersed in carbon spheres.Through high-temperature pyrolysis in nitrogen,Fe₇C₃/NC composites were obtained.Fe₇C₃/NC exhibit excellent ORR activity with a half-wave potential of 0.712 V.3.A novel coordination assisted polymerization assembly strategy is developed to synthesize the atomic Fe dispersed N-doped mesoporous carbon spheres（meso-Fe-N-C）.The meso-Fe-N-C possess a monodispersed particle size of 120.8±5.7 nm,mesopore size of 6.8±0.5 nm,high surface area of 494.7 m² g^-1,and abundant Fe content of 2.9wt%.Benefit from abundant atomic dispersed Fe-N_x active sites and ordered connected mesoporous structures,meso-Fe-N-C exhibit an efficient electrocatalytic activity and long-term stability for ORR in alkaline condition.In 0.1 M KOH,the half-wave potential of meso-Fe-N-C is 0.846 V and no apparent decay is observed in ORR activity even after5000 cycles.The meso-Fe-N-C also show good methanol tolerance.This synthesis method is believed to be applied to design other metal atomic dispersed multifunctional mesoporous materials for diverse catalytic reactions.