The Formation And The Enhancement Mechanism Of Aqueous Hydrogen Peroxide In The Plasma Electrochemical System With Liquid As Anode

Plasma electrochemical system,which uses plasma to replace one of the electrodes in a traditional electrochemical system,has a significant superiority for producing various reactive species by the plasma-liquid interface.These produced high reactive species then dissolve into liquid which can not only result in a series of physical and chemical processes in the system,but also realize some difficult or generally impossible chemical reactions in the liquid.These advantages render the plasma electrochemical system an abroad field of applications,such as in medicine,agriculture,nanomaterial synthesis,water treatment.Most reactions in the plasma electrochemical system are relevant to oxidants and reductants produced by plasma-liquid interactions,therefore,the produced reactives species can somehow influence the liquid chemistry.As a long-lived species,hydrogen peroxide is one of the main components in the plasma liquid system,and the existence of hydrogen peroxide will affect the solution reactions.Some reports demonstrate that the amount of hydrogen peroxide produced in a system when liquid as anode is distinctly less than that produced in a system when liquid as cathode,and this difference is arisen from the formation pathways of hydrogen peroxide.In this thesis,we apply negative voltage(liquid as anode)to ignite plasma to study the formation mechanism of aqueous H2O2.Since the aqueous H2O2(H2O2aq)is formed by the recombination of dissolved OH radicals,we start from the OH radicals to study the H2O2aq formation mechanism by several measures to influence the concentration of dissolved OH.Therefore,we focus on changing the solution environment and reducing the amount of solvated electrons to do our study.Firstly,we use pH buffer solution with different value to study how solution environment affects the formation of aqueous H2O2.Above that,we further replace graphite rod electrodes by fine tungsten wire to study the impacts of solvated electrons.The fine tungsten wire can absorb the electrons produced by plasma irradiation so that the concentration of solvated electrons can be reduced.The results indicated that both the solution environment that is too acidic or too alkaline and the existence of solvated electrons have negative effects on the production of H2O2aq.Except that,we further study how to enhance the yields of H2O2aq.Yet we know that ethanol can react with oxygen and produce OH radicals,then we add ethanol with different concentrations into the liquid to explore the effects of ethanol on the formation mechanism of aqueous H2O2.According to the results,we concluded that adding appropriate concentration of ethanol can enhance the production rate of aqueous H2O2.Finally,we study the redox reactions of electrochemical system by treating AgNO3 solution with discharge plasma,the results showed that the reduction of Ag+and the oxidation of Ag happened spontaneously,and solvated electrons and aqueous hydrogen peroxide play significant parts in the redox reaction.The study of reactive species produced by plasma electrochemical system enable us to apply it to multiple fields so as to realize interdisciplinary application and promote the development of emerging industries.