Confined Fe-based Nanocomposites: Construction And Electrocatalytic Applications

In order to achieve the goal of"double carbon",practice the strategy of healthy China,and create an environmentally friendly,green,low-carbon,healthy and civilized high-quality life,it is an inevitable trend to vigorously develop hydrogen energy and biosensing detection.Catalyic materials are the core of hydrogen production from water electrolysis and electrochemical biosensor.The development of efficient,cheap and stable catalytic materials is the top priority.It is found that the catalytic performance of the catalytic materials is closely related to the composition,particle size,crystal structure,support,pore structure,dispersion state,and specific surface area.Fe is the most abundant transition metal element in the Earth’s crust andis cheap and easy to obtain.This paper focuses on the theme of how to enhance the catalytic activity and stability of catalysts and reduce the cost of materials.Inspired by the confinement effect,a series of highly dispersed nano-catalytic materials with different supports are constructed based on Fe-based nanocomposites by three different confinement strategies,and their electrocatalytic performance and mechanism are studied in depth.1.Highly dispersed FeNiP/NPC composites:Confined construction by electrospinning and HER performanc studyHighly dispersed FeNiP/NPC composites were prepared by chemical bonding atom confinement strategy combined with electrospinning technology for electrocatalytic hydrogen evolution reaction（HER）.The chemical bonding atom confinement strategy was used to form a supramolecular PA-PAN network denoted here as PPA through phytic acid（PA）and polyacrylonitrile（PAN）,which played a limiting effect on metal ions and prevented the agglomeration of metal phosphides in the subsequent pyrolysis process.Among them,PA was a safe and environmentally friendly phosphorus source,PAN was a precursor for in-situ formation of N-doped carbon fibers,and N-doped carbon fibers were used as carriers of metal phosphides.Benefiting from the regulation of carbon fiber electrons by N,P doping,the regulation of hydrogen adsorption by bimetallic phosphides,and the enhanced interaction between in-situ formed supports and metal phosphides,the prepared FeNiP/NPC catalyst exhibits excellent electrocatalytic hydrogen evolution activity and stability.The overpotential of FeNiP/NPC800 is 277 mV at a current density of 10 mA cm^-2 in acidic electrolyte,which is better than that of single metal FeP/NPC800 and Ni P/NPC800.2.Highly dispersed hollow Fe₂P/N-C:Construction by confined nanospace and HER performanc studyHighly dispersed Fe₂P/C composite catalyst with hollow structure was prepared by nanospace confinement strategy and used for HER.Highly dispersed Fe₂P/N-C composite catalyst with hollow structure was prepared by nanospace confinement strategy and used for electrocatalytic hydrogen evolution.The high porous NH₂MIL-88B（Fe）denoted here as NH₂MIL was used as template to prepare the hollow MOF.And PA was used as etching agent to achieve the regulation of the precursor by etching time.During the pyrolysis process,N in NH₂MIL can be doped into carbon,and PA can also be used as a phosphorus source to participate in the synthesis of metal phosphides.Through the modulation of the electronic conductivity of the carbon substrate,the limiting effect of high porosity on the metal,and the full utilization of the internal and external active sites of the hollow structure,the overpotential of NH₂MIL-PA-900 at 10 mA cm^-2 in 0.5 M H₂SO₄ is only 157 mV,and the Tafel slope is 76mV dec^-1,showing excellent HER performance.3.MOF-derived carbon network confined PtFe alloy and HER performanc studyHighly dispersed PtFe alloy porous carbon composites were prepared by nanospace confined strategy using NH₂MIL as template and confined skeleton for HER.The hierarchical porous MOF was prepared by etching NH₂MIL with tannic acid（TA）,and the adsorption of H₂PtCl₆ was completed by impregnation method to realize the modulation of the precursor.Subsequent agglomeration of PtFe is restricted by the network of NH₂MIL itself and subsequent modulation of porosity.NH₂MIL also provides Fe source for PtFe alloy.The particle size of PtFe alloy is less than 10 nm.Due to its small particle size,modulation of hydrogen adsorption energy by PtFe alloy,high dispersion,and hierarchical porous properties,PtFe/C catalyst materials require only 20 mV over potential in 0.5 M H₂SO₄ to achieve a current density of 10mA cm^-2,with a Tafel slope of 26 mV dec^-1,which is superior to commercial 20%Pt/C catalysts.4.MOF-confined growth of prussian blue and its application in electrochemical detection of H₂O₂The well-dispersed and stable PB@NH₂MIL material was prepared by using precursor self-confined strategy and NH₂MIL coordinated unsaturated Fe sites as anchor points to grow prussian blue（PB）for electrochemical detection.Among them,the free coordination Fe sites of NH₂MIL can be used as Fe sources for the growth of PB,and the ordered structure of metal nodes and ligands can limit the growth and aggregation of PB.Based on the catalytic performance of PB@NH₂MIL for H₂O₂,a highly sensitive electrochemical sensor was constructed for the detection for H₂O₂.The linear range is 0.01～1000μM,and the detection limit is as low as 3 nM.