Synthesis And Electro-catalytic Performance Of Hollow Phosphide Nanoparticles

Hydrogen production from electrolyzed water is a possible way to cleanly produce hydrogen energy in the future.Transition metal phosphide nanomaterials have excellent catalytic activity as cathode hydrogen evolution catalysts in electrolyzed water,and hollow-structured nanomaterials are expected to further enhance their catalytic activity.This paper focuses on the synthesis and characterization of hollow iron-based phosphide nanomaterials and their electrocatalytic properties for hydrogen evolution.The specific research contents are as follows:In the first part,we selected iron oxide nanoparticles as the precursor of hollow iron phosphide nanomaterials.We have prepared uniform iron oxide nanoparticles with different particle sizes by selecting solvents with different boiling points to control the synthesis temperature.Hollow iron phosphide nanomaterials were prepared by ion exchange.We studied the effect of phosphating conditions(ie,phosphating temperature and phosphating heating rate)on the morphology and phase of hollow iron phosphide nanomaterials.After electrochemical tests,we found that the activity of the resulting hollow phosphide nanoparticles has a volcanic relationship with the size.If the size is too small,the hollow structure is difficult to use.When the size is too large,the specific surface area of the material decreases,which is not conducive to the hydrogen evolution reaction.Hollow iron phosphide nanomaterial catalysts prepared with an average particle size of 9.1 nm,a phosphating temperature of 350?,and a phosphating heating rate of 20?/min have a very high HER activity.The overpotential required to drive a hydrogen evolution current density of 10 mA/cm2 is only 125 mV.In the second part,we used the previous research results,using MFe2O4(M=Mn,Fe,Co,Cu)type anti-spinel structure nanoparticles as an intermediate,and synthesize iron-based hollow double transition metal phosphide nanomaterials in only two simple steps.We found that the hydrogen evolution activity of the iron-based bimetallic phosphide has a volcanic relationship with the atomic number of the second metal.Co-Fe-P/C is the catalyst with the highest HER activity.When the loading is 0.2 mg·cm-2,the over-potential required to drive the current density of 10 mA/cm2 is only 97 mV,and its corresponding Tafel slope value is 55 mV·dec-1.The results show that the incorporation of highly electronegative cations stabilizes the surface FeP active center through possible electron modulation effects,which in turn causes the catalyst to exhibit high HER activity and high stability.