Controlled Synthesis Of FeCo Composite Oxides And Their Oxygen Precipitation Properties

With the expanding global energy demand and deteriorating environmental problems,the energy crisis continues to affect our development,and the development of new clean and renewable energy sources has become a research focus for researchers.At present,a promising method for hydrogen production is electrolysis of water.The oxygen evolution reaction（OER）in electrolytic water is a four-electron reaction,and the reaction process is slow,resulting in low efficiency of hydrogen production from electrolytic water.Although precious metal catalysts have considerable catalytic performance,they are expensive and cannot be used in large quantities in industry.Transition metal oxides are favored for their oxidation resistance,easy storage,and low price.Therefore,this paper focuses on the controlled synthesis of metal hydroxyl oxides and metal layered double hydroxides and further analysis of their OER performance.（1）FeCoCu was used as the base element,and catalyst samples with different compositions were synthesized by adding Mo,Ni,Mn,and Al elements.The experimental results show that with the superposition and modulation of the elements,the synergistic effect between the elements is enhanced and the performance shows an upward trend.The synthesized FeCoCu MoMnOOH shows the optimal OER performance during the electrolysis of water.Its current density of 100 m A/cm² can be achieved with only 227 m V and the Tafel slope of 14.94 m V/dec.The stability of the samples was regulated by controlling the ratio of Cu elements in the synthesized samples,and the results showed that the appropriate ratio of Cu elements can improve the stability problem of FeCoCu MoMnOOH.The corrosion of the copper foam skeleton was minimized at a molar ratio of Fe to Cu of 1:1,and the best hardness of the sample was achieved.The performance was basically non-degradable in the 30h chronoamperometry test,which confirmed that it could maintain a good stability,mainly due to the reversible reaction between Fe³⁺and Cu.The overall excellent performance of the synthesized samples is mainly due to the modulation of the electronic structure around Fe and Co elements by Mn elements,which can optimize the OER performance of the samples and achieve efficient water electrolysis.（2）The FeCoNi-LDH nanosheets were synthesized by regulating the current density and deposition time of electrodeposition.The loading of the samples deposited gradually increased with the increase of the deposition current density and time,and the catalyst loading presented the most suitable condition under the preparation conditions of 100 m A/cm² and 300 s.In addition,the size of Ag particles on FeCoNi-LDH was regulated by controlling the concentration of Ag NO₃ solution using the in-situ reduction method.It was found that the introduction of Ag particles had an enhancing effect on the OER performance of the bilayer hydroxide.The catalytic performance of the synthesized Ag@FeCoNi-LDHperformed better at the concentration of Ag NO₃ solution of 0.05 M.The overpotential corresponding to 100m A/cm² was as low as 207 m V,and the corrending slope of Tafel is 19.15 m V/dec.This is mainly due to the formation of heterointerface between Ag and FeCoNi-LDH providing an efficient electron transport channel,which is beneficial to increase the reaction rate of the sample OER.By comparing the two experimental schemes in this paper,it was found that the performance of Ag@FeCoNi-LDH catalyst in OER was relatively good,mainly because the introduction of Ag particles further enhanced the OER performance of FeCoNi-LDH,which indicated that the appropriate size of Ag particles and the construction of heterointerface of precious metal Ag and FeCoNi-LDH could effectively enhance the OER performance.