Synthesis Of Nickel Cobaltate-Based Composites And Its Electro-Catalytic Performance For Methanol

In this paper,based spinel metal oxide NiCo2O4 compounds is synthesized and investigated the activity of the composite in the methanol oxidation reaction.The performance of direct methanol fuel cells hinges on the activity of the catalyst.To enhance the electro-catalytic activity,a flower-like nanostructure assembled from thin Au/NiCo2O4 nanosheet is synthesized via a microwave process combined with deposition-reduction method,where the Au nanoparticles are well dispersed on the surface of the NiCo2O4 nanosheet.The Au/NiCo2O4 composite nanoflower is successfully applied in the methanol oxidation reaction and its electro-catalytic performance is probed by electrochemical method,which exhibits excellent electro-catalytic qualities towards methanol oxidation reaction in KOH solution,such as high current densities(135.9 mA cm-2)at 0.60 V(vs.SCE)and desirable electro-oxidation stability(94%)after 500 cycles.The activity of NiCo2O4 is significantly increased by a handful of Au for methanol electro-oxidation.Au is highly electronegative and can act as an electron trap,stimulates the generation and stabilization of Co4+ and Ni3' as the active sites for methanol oxidation reactions.In this process,it is unavoidable to use a binder,which reduce the active area;in addition,the interface resistance between the material and electrode affects the electron collection efficiency.These limit the further application of material.NiCo2O4 grown on the surface of nickel foam avoids the use of binder and eliminates the interface resistance.The current density of prepared NiCo2O4 reaches 153.6 mA cm-2 in the 1M KOH+0.5M methanol solution.Obviously,the performance of prepared NiCo2O4 electrode is better than the Au/NiCo2O4 modified electrode.Furthermore,designing and synthesizing core/shell materials are a valid method to increase the electrochemical property.The hierarchical NiCo2O4@NiFe-layered double hydroxide core/shell arrays are successfully constructed via a stepwise hydrothermally grown and used for methanol oxidation reaction.With the assistance of the unique nanostructures and the interaction between NiCo2O4 nanowires and NiFe-layered double hydroxide nanosheets,the composite displays evidently melioration in conductivity,accelerates the eletrons transfer,contains myriad active centers and shortens the diffusion raidus of molecule in solution.Thus,the sample exhibits outstanding electrochemical character including a high current density(228.4 mA cm-2)and good stability(96%current density retention after 500 cycles).Our trials indicate that the hierarchical NiCo2O4@NiFe-layered double hydroxide core/shell nanowire arrays have great potential for applications in elecrocatalysis.