Preparation Of Nanoporous Palladium-based Catalysts And Their Application In Formic Acid Fuel Cells

With the ever-increasing demand for energy,the consumption of fossil fuels and the total amount of CO2 emissions are rising rapidly,the energy reform of"clean,low-carbon,safe,and efficient"has become the general trend,and fuel cell technology is an important member of clean energy technology.As one type of fuel cell,direct formic acid fuel cell（DFAFC）has the characteristics of less pollution,abundant fuel sources,easy storage and transportation,and high energy efficiency.It is an important research direction of fuel cell technology.Aiming at the problems of high cost and scarce reserves caused by the use of Pt and Pd as electrocatalysts in formic acid fuel cell anodes.At the same time,traditional carbon-supported catalysts have problems such as high Pt and Pd loading,susceptibility,and serious corrosion of carbon supports,which are serious obstacles.The commercial application of formic acid fuel cell.The nanoporous metal catalyst with high porosity and high specific surface area,with its bi-continuous self-supporting 3D network structure,can firstly avoid the corrosion problem of the carbon support in the supported catalyst;secondly,the pore structure and coordination atoms that are conducive to mass transfer The abundant ligament surface enables the nanoporous metal catalyst to achieve excellent catalytic activity and long-range stability under low Pd loading.This paper focuses on the research of nanoporous Pd-based catalysts with low Pd loading.The specific research contents are as follows:（1）NPG-Pd core-shell catalysts with different catalytic surface morphologies were controllably synthesized by three methods:under-potential deposition,differential pulse electrodeposition and chemical displacement.Combining electrochemical means and electron microscopy characterization analysis and screening the optimal synthesis method.The evolution of the catalytic surface during the deposition of Pd on NPG was studied,and the structure-activity relationship of different loadings of NPG-Pd was analyzed by combining electron microscopy characterization,electrochemical testing,and membrane electrode testing.Studies have shown that with the increase of the number of Pd atoms in the shell layer,the catalytic surface exhibits three stages of epitaxial growth-rough microstructure-twisted ravines.Under the 12μg load,the active area is the largest and reaches the peak mass activity,which is 7 times that of commercial Pd/C.The performance of the membrane electrode is normalized to the mass power density of the palladium loading,which is 126 times that of the commercial Pd/C catalyst.（2）The Pd Cu Au ternary alloy catalyst was designed and synthesized by the method of layer-by-layer pulse electrodeposition combined with annealing,using nanoporous gold as the substrate.The intrinsic activity(15 m A·cm^-2)and mass activity(6012 A·g _Pd^-1)of the constructed NPG-Pd Cu Au alloy catalyst are 15 times and 14 times that of the quotient Pd/C,respectively.In addition,thanks to the multiple synergistic effects of the Pd Cu Au ternary alloy,the carbon monoxide resistance and durability of the catalyst are significantly improved compared to NPG-Pd.The normalized mass specific power density of the catalyst in the single cell to the palladium loading reaches 9.3W·mg^-1,which is 186 times higher than commercial Pd/C.The introduction of gold reduces the d-band center of the catalyst and adjusts the carbon monoxide center.The binding energy of the body.At the same time,gold modifies the electronic structure of palladium and exerts a significant electronic effect.Copper mainly improves the carbon monoxide resistance of palladium by adsorbing free hydroxyl groups.In addition,gold can significantly stabilize copper and reduce the electrochemical corrosion of copper in an acidic environment,thereby ensuring the long-term stability of the material structure.