The Preparation Of Transition Metal Cobaltates And Its Electrochemical Performance Study

Pt-based materials have been used in the field of fuel cells as a very effective catalyst,their high-volume,low-yield and methanol poisoning problems have hindered their large-scale commercial production and application.In view of this,a great deal of investigation and research work has been carried out to find low-cost and durable alternatives.It has been found that transition metals have multiple oxidation states and their catalytic properties can be controlled by chemical composition adjustment.In addition,simple synthesis methods can be used to produce samples with different morphologies.For different nanomorphology catalysts,provide different interface areas to effectively affect the catalytic performance.Therefore,such complex metal oxides have great potential as a new alternative to noble metal catalysts.Quasi-two-dimensional ultrathin multicomponent transition-metal oxide nanosheets have been considered as a promising candidate of catalyst in eco-friendly energy storage/conversion systems due to their low price,large specific surface area,multiple active sites,and high electron transfer efficiency.In this work,novel mesoporous ultrathin Co3O4 nanosheets have been successfully obtained through the simple combination of hexamethylenetetramine-assisted hydrothermal reaction and calcination in an air atmosphere.The mesoporous Co3O4 nanosheets exhibit a micron-sized planar area and ultrathin thickness,suggesting a high specific surface area,thus facilitating the charge transfer and raise efficiency of reactant exchange to enhance the overall performances in electrochemical reaction.In a three-electrode system consisting of Hg/HgO reference electrode,Pt counter electrode,catalyst-covered glassy carbon working electrode and 0.1 M KOH electrolyte,the oxygen reduction reaction(ORR)performances of the mesoporous Co3O4 nanosheets were systematically studied using a rotating disk electrode.Results indicated that the mesoporous Co3O4 nanosheets had excellent catalytic activities towards the ORR(0.84 V onset potential and 5.3 mA/cm2 limited current density),and the Co3O4 nanosheets catalyst primary favors direct 4-electron pathway for the reduction of oxygen in alkaline aqueous is similarly to a commercial Pt/C electrocatalyst.Furthermore,this catalyst exhibited a superior durability and methanol tolerance compared to those of the commercial Pt/C catalyst.In order to explore the electrocatalytic properties of more transition metal cobaltates.Ultrathin porous spinel structure ZfnCo2O4 nanosheets(ZCONSs)are successfully prepared by a facile combination of hexamethylenetetramine-assisted mild water bath reaction and a heat treatment process.The ultrathin film shape and porous of as-prepared ZCONSs were demonstrated by a transmission electron microscope(TEM).Such a specific nanostructure of as-prepared ZCONS provided an efficient charge transfer process,as well as an efficient mass transport processes.Therefore,in the oxygen reduction reaction(ORR)test,ZCONS shows good electrocatalytic ability.Additionally,because of the ultrathin nanosheets possess enough extra free space for alleviating so that endow long-term cycling stability,make the catalyst possesses superior durability and excellent methanol tolerance ability.