Doping, Modification And Electrochemical Performance Of Oxygen Electrode Catalyst Pr 2 NiO 4

"Layered" oxides with the K₂NiF₄ structure exhibit good oxygen electro-catalytic property,due to the ready intercalation of oxygen species into the tension inter-layers.In this thesis,Ln₂NiO₄?Ln=La,Pr,Nd?were prepared by EDTA-citrate method and characterized using XRD,XPS,FT-IR et al.The electrochemical measurements indicated that Pr₂NiO₄ had the highest ORR electro-catalytic property with the onset potential?-0.19 V?and the peak current density??3 mA cm-2?.It is due to the high content of hydroxide on the surface,which was easily replaced to O22-.Among the series of material Pr_1.9M_0.1NiO₄?M=Ca,Sr,Ba?,Ca-doped material was found to have the highest mean valence of Ni and the content of surface hydroxide,which exhibited the best ORR property.The surface hydroxide content in Pr2-xCaxNiO₄ changed with the Ca doping concentration and showed a volcano curve shape,whereas the Ni-O covalence increased monotonically.The material Pr1.8Ca0.₂NiO₄ gave the best ORR catalyst properties,due to the joint action of Ni-O covalence and the surface hydroxide content.In the investigation of the electrode reaction kinetic on the surface,charge-transfer process and mass-transfer process were successfully identified.In order to promote the bi-functional properties,Pr1.4Ca0.6NiO₄-NiO composite material was prepared.The material showed extremely high current density in OER,about 3.5 times better than that of Pr1.8Ca0.₂NiO₄.Cu modified Pr1.4Ca0.6NiO₄-NiO improved the ORR onset potential with +0.04 V shift,and 25%increase of OER current density.The Nyquist plot displayed that the charge-transfer resistance of the Cu modified material was just 58.5%that of Pr1.4Ca0.6NiO₄-NiO.It demonstrated that Cu accelerated the charge-transfer process,and thereby the ORR and OER properties were both improved.