Preparation And Electrocatalytic Performance Of Novel Iron-based Catalysts For Oxygen Evolution

Due to the non-renewability of fossil energy,energy demand and the urgency of climate change,people have attached great importance to the future security of our energy and the sustainable development of society.Hydrogen energy is known as the "ultimate energy source" for humans because of its high energy density and calorific value.In the current hydrogen production process,water splitting hydrogen evolution has become a research hotspot,but the high cost and limited reserves of commercially available precious metal catalysts hinder their large-scale use.Transition metal-based catalysts have the advantages of high reserves,low cost and unique electronic structure,and have great application prospects in the field of water splitting.Among them,iron-based compounds(such as iron-based oxides,oxyhydroxides,etc.)have the advantages of being natural rich,non-toxic,and having high catalytic performance under strong alkaline conditions,and are suitable for use in electrochemical fields such as electrocatalysis and supercapacitors.As a promising active material,fluorine-based compounds have some advantages over other commonly used materials such as sulfides,phosphates,oxides and nitrides,and have received more and more attention.Therefore,iron-based fluorides and oxides are studied in this paper.Through the micro-regulation or ion doping,a new transition metal catalyst is obtained to improve its water splitting oxygen evolution performance,and its catalytic mechanism as an electrolyzed water catalyst is explored.It provides a new idea for electrolysis of oxygen evolution catalysts.First,the precursor ferric fluoride(Fe F3)was successfully replaced the O atom with F atoms at 210 °C by a simple solvothermal method to obtain pure Fe2OF4 nanorods.As time goes on,the Fe F3 gradually changed to Fe2OF4 under the action of n-propanol.The pure nanomaterials were obtained at the reaction time of 20?22 h.As the reaction continued,the nanorods were both ends.The splitting began,and the Fe element was slowly reduced to Fe2+,which eventually turned into Fe F2.The LSV data shows that Fe2OF4/NF can achieve a current density of 100 m A cm-2 with only 237 m V overpotential for OER,and the corresponding Tafel slope of LSV is only 39.8 m V dec-1,which is better than the precursor Fe F3,Fe3O4 and commercial catalyst Ru O2.Fe2OF4/NF was used as a bifunctional catalyst for overall water splitting,the appliedvoltage at 10 m A cm-2 is 1.604 V,while the Fe2OF4/NF can remain stable for 1000 h under 500 m A cm-2.This is because the presence of F improves the interfacial charge transfer efficiency of the oxide,and the presence of O can effectively reduce the polarity of the Fe-F bond,so that the internal resistance of the material is greatly reduced.At the same time,the base foam nickel is also involved,forming Ni-O-Fe bond,and the simultaneous presence of Ni and Fe also greatly enhances the electrocatalytic oxygen evolution activity of the material.On the basis of the above research,Fe3O4 was electrodeposited on a nickel foam substrate and related physical characterization and electrochemical characterization were carried out.The electrocatalytic performance was studied as a self-supporting electrode.Then,a simple F-doped was carried out to explore the effect of F doped on the electrocatalytic oxygen evolution of Fe3O4/NF.The study found that both the deposition temperature and the concentration of Fe3+ ions play an important role in the deposition process.At the same deposition temperature,as the concentration of Fe3+increases,the deposition rate also increases.The OER polarization curve shows that F-doped Fe3O4/NF has a lower overpotential at the same current density,indicating that the addition of F makes the electrocatalytic oxygen evolution performance of undoped Fe3O4/NF significantly improved.At the same time,the Tafel slope also indicates that F-doped Fe3O4/NF has a stronger kinetics of oxygen evolution,because the F-doped oxide matrix can increase the electrical conductivity and absorption coefficient of the system,thereby accelerating the charge transport in the electrocatalytic reaction.