Design And Synthesis Of Catalysts For Electrochemical Water Splitting And Oxygen Reduction Reaction

Recently,the consciousness of the environment and the limited energy has gained more and more popularity.To reduce the dependence on non-renewable energy resource such as petroleum and chemical energy,there is an urgent need to develop clean,cheap,convenient,and efficient supply mode for energy.During the past years,the researches and developments on battery technologies with low pollution have attracted much attention.Specially,the renewable fuel cells,the rechargeable metal-air battery,and water electro-splitting have been the top issues around the world.These technologies are fundamentally based on the electrocatalysis processes,which need highly efficient catalysts to reduce the energy consumption.To date,the commonly practicable catalysts for electrodes mostly consist of precious metals like Platinum,Iridium,and Ruthenium etc.for their excellent properties.Nevertheless,the limited resources and the relative high price of precious metals heavily hinder their large-scale applications and the development of the new energy technology.Therefore,it is highly desirable to design and develop novel and efficient catalysts under these circumstances.For the next generation of catalysts,it is critical to not only reduce the consumption of precious metals like Platinum,but remarkably enhance their electrocatalytic performance especially the mass activity.Moreover,the durability of the catalysts should be carefully considered as well.As we discussed above,it has been a hot topic to develop highly efficient alloy catalysts and novel non-precious metal catalysts such as perovskite-type oxide catalysts.Herein,we focus on the synthesis of perovskite-type oxide and Pt-Cu alloy catalysts,which hold high conductivity and abundant active sites.This paper is divided into five chapters and the main content of each chapter was as follows:In chapter 1,the background of the electrochemical catalysis were generally introduced firstly.Then we summarized the fundamental mechanism of HER,OER,and ORR reactions and benchmark catalysts of the three reactions.Combined with the review on the recent process in electrochemical catalysis,we mainly introduced the strategies on manipulating the morphologies,size,and composition of precious metals to improve the electrocatalytic performance.Furthermore,we also discussed the effect of perovskite-type oxide catalysts on electrochemical catalysts.In chapter 2,we introduced the synthesis of Pt-Cu hierarchical quasi great dodecahedrons(HQGDs)with 5-fold symmetry.It was found that the amount of KI and the molar ratio of the precursors were critical for the formation of HQGDs.The HQGDs exhibited much more outstanding HER activity compared with the commercial Pt/C catalysts because of abundant twinning defects and the hierarchical frame structure.In the chapter 3,we synthesized WO3 with oxygen defects modification by liquid-phase ultrasonic exfoliation.It was found that the valence of W changed from 6+ to 5+ due to the existence of oxygen defects,and the coordination number of W atoms declined obviously.Electrochemical test suggest that the HER perfromance of WO3 with defects was better than that of WO3 bulk,and even comparable with the commercial Pt/C catalysts.It is probably because the oxygen defects regulate the electronic structure of tungsten atom,and the hydrogen adsorption free energy is close to zero,result in improving the catalytic performance.In chapter 4,we successfully synthesized the double perovskite-type oxide catalysts with oxygen vacancies and their corresponding single counterparts by virtue of sol-gel methods.It was found that the double perovskite-type oxide catalysts exhibited bifunctional catalytic properties for OER and ORR together with excellent stability,which overcame the disadvantages of single perovskite-type oxide catalysts.These properties were ascribed to the relative high conductivity and the stable structures of double perovskite-type structures.In chapter 5,we carefully summarized the key points in this paper and proposed the prospect of electrochemical catalysts.In addition,we also elucidated the opportunity and challenge in electrochemistry from the yields,the structure-function relationship,and the in situ characterization for electrochemistry.