Surface Modification And Performance Of GdBaCo₂O_5+δ-based Bifunctional Oxygen Electrodes

The increasing energy and environmental issues have prompted people to eagerly develop low-cost,high-performance,clean and sustainable energy storage and conversion devices.Reversible metal-air batteries,fuel cells and electrolytic cells are considered to be electrochemical devices with a wide range of applications.However,due to the slow kinetic rate of the oxygen reduction reaction（ORR）and oxygen evolution reaction（OER）on the oxygen electrode in these devices.As a result,these devices cannot provide electricity quickly and stably.Therefore,the development of high-efficiency and low-cost dual-functional oxygen electrode catalysts has become an area of focus for researchers.In recent years,double perovskite Ln Ba Co₂O_5+δ（Ln=Sm,Nd,Gd and Pr）catalyst materials have attracted much attention due to their ideal layered structure,high electronic and ion mixed conductivity.Among them,Gd Ba Co₂O_5+δ（GBCO）is the main research material of this article.It is reported that the preparation of a composite oxygen electrode catalyst can significantly improve the dual catalytic performance of the material.In this paper,the double perovskite type GBCO is surface modified by using cobalt,cobalt and nickel,and silver to obtain a composite oxygen electrode catalyst and improve the performance of catalyst material.In this paper,GBCO materials were synthesized high temperature solid phase method,GBCO/Co（NO₃）₂materials calcined at different temperatures.Among the GBCO/Co（NO₃）₂materials,the ORR curve of the GBCO/Co（NO₃）₂material prepared at a calcination temperature of 350°C has the largest potential value of 0.594 V and the smallest Tafel slope.Although the value of the number of transferred electrons n is small,the overall view of impregnation and calcination treatment improves the ORR performance of the material.In terms of OER,the material has the smallest overpotential 1.693 V,the highest polarization current density and the smallest Tafel slope of 129.87 m V dec^-1.Compared with pure GBCO,the electric double layer capacitance C_dlof the sample after the impregnation and calcination treatment is significantly improved,and it still maintains high stability under alkaline test conditions,so it has a wide range of application prospects.The GBCO material co-impregnated with Co and Ni elements in different proportions is prepared by the impregnation method.Compared with other co-impregnated GBCO ratios of Co and Ni,the material prepared when the impregnation ratio is 1:1 has the largest potential value at the same current density.It is0.595 V,has a small Tafel slope,and the maximum number of transferred electrons n.In terms of OER,the material has the smallest overpotential of 1.673 V,the highest polarization current density and the smallest Tafel slope,as well as strong catalytic stability.In addition,the electric double-layer capacitance Cdl of the sample treated with Co and Ni co-impregnated is significantly higher than that of Co-impregnated GBCO alone.GBCO/Ag materials calcined at different temperatures were successfully prepared by impregnation method.Compared with other GBCO/Ag catalyst materials at calcination temperature,the GBCO/Ag material prepared at a calcination temperature of450℃has the smallest potential value and the highest polarization current density at the same current density,and at the same time has the smallest transfer The number of electrons is n.Although the Tafel slope value of GBCO/Ag material prepared at a calcination temperature of 500°C is the smallest,the overall ORR performance of the material is improved by impregnation and calcination.In terms of OER,the GBCO/Ag composite oxygen electrode catalyst material prepared at a calcination temperature of500℃has the smallest overpotential,the highest polarization current density and the smallest Tafel slope,as well as strong catalytic stability.In addition,the electric double layer capacitance C_dlof the sample after the impregnation and calcination treatment is significantly higher than that of pure GBCO.The GBCO/Co（NO₃）₂material calcined at 350°C was synthesized by the impregnation method,the GBCO material was prepared when the co-impregnation ratio of Co and Ni was 1:1,and the GBCO/Ag material calcined at 500°C.When the Co and Ni co-impregnation ratio is 1:1,the minimumΔE value of the GBCO material is 1.078V,which shows that it has the best dual-functional catalytic performance.