Preparation And Electrochemical Performance Of Prussian Blue Analogs Derived Nanomaterials

The electrochemical decomposition of water to produce hydrogen is an important means to effectively alleviate the current energy crisis.Among them,the preparation of highly active and stable oxygen evolution reaction(OER)catalysts is the key to promoting the practical application of electrocatalytic water decomposition technology.Due to the shortcomings of precious metal-based catalysts such as low reserves and high prices,it is difficult to be widely used.Therefore,the development of highly-activity/highly-stability electrocatalytic materials with rich reserves and low prices has become a current research focus.Prussian blue analogues(PBA)are considered as the ideal precursors for the preparation of highly active OER catalysts due to their large specific surface area and controllable metal center ions.Therefore,this paper makes full use of the advantages of PBA materials.With NiFe PBA as the precursor,NiFe PBA is converted into a highly active OER catalyst by electrochemical activation method and low temperature carbonization method,respectively.The relationship among morphology,structure and OER activity is discussed,which provides new ideas for designing highly active and stable OER catalysts.The main research contents and results obtained include the following aspects:(1)NiFe PBA@Ni(OH)2/NF,a self-supporting composite material,was successfully prepared on the nickel foam substrate by hydrothermal method and ion exchange method.NiFe PBA@Ni(OH)2/NF,was used as the precursor,which was converted to highly active Fe-doped Ni(OH)2 by electrochemical activation.The catalyst exhibits excellent OER activity.At a current density of 10 mA cm-2,the corresponding overpotential is only 256 mV,which is significantly lower than the unactivated NiFe PBA@Ni(OH)2/NF(290 mV)and powder samples(480 mV),showing excellent stability after 12 h testing.The experimental results show that its excellent activity and stability mainly include the following aspects.First,the surface of the amorphous Ni(OH)2 generated after electrochemical activation has more defects and more active sites.Second,during electrochemical activation,Fe is doped in-situ into Ni(OH)2,which effectively regulates the electronic structure and improves the kinetics of water oxidation Finally,a self-supporting electrode based on nickel foam was constructed,which improved the electrode’s conductivity and stability.(2)The FeNi@NC nanocatalyst with high activity was successfully prepared by chemical precipitation and subsequently heat treatment with NiFe PBA as precursor.The effects of heat treatment temperature,heat treatment atmosphere and type of core alloy on the morphology/structure of the catalyst were systematically studied.At the same time,the relationship between morphology and structure with its electrochemical performance of the catalyst was studied in depth.The results show that FeNi@NC obtained after treatment at 350℃ in H2/Ar atmosphere has the best OER activity.In alkaline electrolyte,the corresponding overpotential is only 237 mV at a current density of 10 mA cm-2.And it remained stable after 12 h test.This is mainly due to the transformation of the sample into a porous three-dimensional cube structure after low temperature heat treatment,exposing more active sites.Secondly,after the low temperature heat treatment,the carbon shell is amorphous and has a large number of defects,which increases the number of active sites in the carbon layer and promotes charge transfer between the core metal and the carbon layer.Finally,the N-doping generated in situ during carbonization process further optimizes the electronic structure of the carbon layer so that it exhibits excellent OER activity.