Preparation And Electrochemical Performance Study Of Multi-Component Alloyed Nanomaterials

Since the Industrial Revolution,the heavy abuse of conventional fossil fuels has led to serious energy crisis and environment pollution issues.To mitigate these problems,it is crucial to develop new,green and clean energy storage and conversion devices for sustainable development of the mankind.Hydrogen possesses the merits of high energy density,cleanliness and no pollution nature,which is considered as the green and environment-friendly secondary energy sources with great potential.Among numerous technologies for hydrogen production,electrocatalytic overall water splitting(OWS)has attracted much attention because it can achieve hydrogen production with high purity.Additionally,zinc-air batteries(ZAB s)hold the advantages of high theoretical energy density,low cost,and good safety,which are generally considered as the new type of energy storage device with practical application value.Nevertheless,when practically using these two techniques,there are still some obstacles such as slow electrode reaction rates and short operation life.To realize the commercialization of ZABs and hydrogen production by OWS,it is critical to fabricate catalysts with high performance,good stability,and relatively-low cost for electrode half-reaction processes,including hydrogen evolution reaction(HER),oxygen evolution reaction(OER)and oxygen reduction reaction(ORR).In this thesis,a series of multi-component alloyed nanomaterials are prepared by green,simple and efficient synthetic methods such as hydrothermal and in-situ reduction.The relationships among the microscopic morphologies,charge properties and electrochemical performances for the catalysts are analyzed by various characterization means.The main contents are as follows:(1)Using Pt,V and Co salt as metal sources,PtVCo ternary alloyed nanomaterials are prepared by one-step hydrothermal method,and used for electrochemical tests toward HER,OER,ORR,etc.On the premise that the initial loading amount of Pt is set constant,the comparison samples,PtV and PtCo,are also prepared.Through transmission electron microscopy(TEM)analysis,PtVCo displays a dendrite shape with an individual dendritic particle of about 75.8±25.0 nm,while PtV and PtCo embrace slight or heavy aggregation phenomena.Compared with the counterparts,PtVCo shows the best HER(the overpotential of 0.045 V in 1 M KOH),OER(the overpotential of 0.36 V in 1 M KOH)and ORR(the onset potential of 0.89 V in 0.1 M KOH)activities.Meanwhile,the HER and ORR performances of PtVCo are comparable with that of commercial Pt/C,and the OER performance is close to that of IrO2.The stability of PtVCo is also much better than that of Pt/C and IrO2.(2)As the PtVCo ternary alloys possess outstanding hydrogen evolution,oxygen evolution and oxygen reduction capabilities,the overall water splitting performance is examined,and a self-assembled Zn-air battery device is also constructed.When OWS and ZABs tests are executed practically,it can be observed that:(i)Among the series of samples,the voltage gap of PtVCo for OWS is 1.64 V,which is not only much lower than that of PtV and PtCo,but also lower than commercial Pt/C and IrO2;(ii)As for the zinc-air battery test,the charge-discharge voltage gap of PtVCo is narrow,only about 0.88 V,and the open-circuit voltage is approximately 1.42 V.PtVCo exhibits a maximal power density of 235 mW cm-2,of which is markedly superior to that of commercial Pt/C.(3)Metal organic framework,UiO-66-NH2,is employed as the precursor,and RhxRu100-x(x represents the initial atomic percentage of Rh in RhRu alloys)nanoparticles are confined into the cavities of UiO-66-NH2 by in-situ reduction,which is subsequently applied for HER test under all pH values.Among the RhxRu100-x@UiO-66-NH2 series,Rh50Ru50?UiO-66-NH2 demonstrates the best HER activities.The overpotentials of PtVCo for HER in 0.5 M H2SO4,1 M PBS and 1 M KOH are 77 mV,111 mV and 176 mV,respectively,which are distinctly lower than that of other samples in the series and commercial Ru/C catalyst.Furthermore,Rh50Ru50@UiO-66-NH2 exhibits excellent stability and corrosion resistance toward the electrolytes at a wide pH range.