Study On The Electrochemical Behavior Of Hydrazine Hydrate On Platinum Ultramicroelectrode And Single Platinum Nanoparticle

Hydrated hydrazine(HH)has been widely used in the fields of material preparation,metal antisepsis,fuel cell,and analytical determinations.These applications have promoted the development of HH reaction mechanism to a certain extent,especially the mechanism of HH electrocatalytic reaction.Currently,the clear explanation of the electrocatalytic mechanism is the catalysis in strong acid and alkali solution,HH undergoes 4e transfer reaction,and nitrogen is the final product.Moreover,there are also a large number of applications of HH in non-strong acidic and alkaline conditions,such as the HH electrochemical detection and HH electrocatalytic oxidation,etc.However,the catalytic mechanism under neutral conditions is less studied.Those mechanisms have reported are different from each other,and the relevant researchers also do not give a reasonable explanation.This will inevitably bring trouble to the application of HH.In this work,we have fully studied the electrocatalytic mechanism of HH by using a platinum ultramicroelectrodes(Pt UME)at first.Since HH is a weak alkaline,it ionizes under neutral conditions to produce two species,making the catalytic reaction has two steady state currents.However,the concentration of the species that participated in reaction was not equal to the actual concentration of them in the solution.And the values of two steady-state current were affected by the supporting electrolytes.This phenomenon was different from the catalytic reaction occurred in strong acid or alkaline solution.We then conducted an in-depth study of this phenomenon,including influence of the supporting electrolytes from acidic to neutral,finally to alkaline,and the influence of supporting electrolyte concentration.The mechanism can be stated as:On the one hand,when the supporting electrolyte is insufficient,the limiting diffusion current will be affected by the‘H~+field'formed in the catalyst;on the other hand,the species participated in the catalytic reaction is affected by the nature of the supporting electrolyte.When sodium sulfate,sulfuric acid,or sodium hydroxide is employed as the supporting electrolyte,the steady state currents are mainly affected by the original H~+in the solution and the H~+generated in the catalysis.When the buffer salt serves as the supporting electrolyte,the steady-state current appears to be affected by thermodynamic equilibrium and the thermodynamics of catalytic reaction of HH,and H~+absorption capacity of buffer salt.This mechanism can provide useful information for the electrocatalytic reaction with HH as the redox mediator.Then,we studied the catalysis of HH on single platinum nanoparticle(Pt NP).As we all know,metal nanoparticles have a high specific surface area and high catalytic activity.In particular,platinum nanoparticles have been widely used in catalytic reactions.Therefore,whether the single Pt NP has a more outstanding catalytic performance to HH than Pt UME triggering our interest.With the single-NP collision model,we studied the behavior of HH catalysis on single Pt NP.The catalytic properties of Pt NP to HH in the potential range same as HH catalyzed by Pt UME were determined.The results showed that in the potential range of two steady states,the redox media catalyzed by single Pt NP were same as the Pt UME.This is to say single Pt NP did not showed a superior catalytic performance over UME under the experimental conditions.The only difference was that the catalysis of Pt NP to HH did not affected by the H~+generated in the catalytic reaction.In addition,this method can also be used to explore the catalytic performance of single NP with different crystal forms and different compositions.Thus,we can put the catalytic research of nanoparticles into single-particle level.