Preparation Of Graphene Supported Pd Catalyst And Investigation Of Its Electrocatalytic Performance For Formic Acid Oxidation

Direct formic acid fuel cells?DFAFCs?have great potential in the field of low temperature fuel cells with a number of advantages such as wide fuel sources,easy storage and transportation,environmental protection.It was found that Pd catalyst exhibits exceptional electrocatalytic performance in formic acid oxidation,but the high price of Pd metal limits the commercialization of DFAFC to a certain extent.How to further improve the utilization rate of precious metal Pd,reduce the cost,increase the dispersion of Pd nanoparticles and decrease the average particle size is still an urgent problem to be solved.The particle size and dispersion of Pd catalyst are directly dependent upon the choice of carbon supports.Graphene has unique two-dimensional planar structure,high specific surface area and excellent physical and chemical properties.While graphene as a catalyst support,it can effectively improve the conductivity of the catalysts and the diffusion rate of electrolyte ions,thereby improving the overall catalytic activity of the catalyst.In this paper,Pd/RGO catalysts were prepared by two-step reduction in liquid phase and vacuum impregnation with graphene oxide as support precursor.The effects of different process parameters on the morphology and electrocatalytic properties of the catalysts were systematically investigated.The main results are summarized as follows:?1?Pd/RGO catalyst materials were prepared by two-step reduction in liquid phase.The morphology and structure of the catalyst materials were characterized by XRD and TEM.The electrocatalytic oxidation performance of the catalyst materials for formic acid was tested by cyclic voltammetry and chronoamperometry.The results showed that the average particle size and dispersion of Pd particles were significantly affected by pH and reduction temperature.The particle size of Pd particles was about2.9 nm when the pH was 6 and the reduction temperature was 0?.In addition,the pH and the reduction temperature were the main factors affecting the electrocatalytic performance of Pd/RGO catalyst.The optimum experimental conditions for the preparation of Pd/RGO catalyst by two-step reduction in liquid phase are as follows:the concentration of PdCl₂ is 1.5 mM,the pH is 6,the reduction temperature is 0?,and the reduction time is 2 h.The corresponding electrochemical active area is 3.02cm² and the maximum oxidation peak current density is 4.80 mA·cm^-2.?2?Pd/RGO catalyst materials were prepared by vacuum impregnation method.The morphology and structure of the catalyst materials were characterized by XRD and TEM.The electrocatalytic oxidation performance of the catalyst materials for formic acid was tested by cyclic voltammetry and chronoamperometry.The results show that the average particle size of Pd particles and the reduction degree of graphene oxide are greatly affected by the loading amount and heat treatment temperature.The electrochemical properties of Pd/RGO catalyst materials show a trend of"first increasing and then decreasing"with the increase of the loading amount and heat treatment temperature.The optimum preparation conditions are loaded of 3wt%,pH of 8,heat treatment temperature of 500?,and heat treatment time of 2 h.