Preparation Of Pd - Based Catalysts For Direct Formic Acid Fuel Cells And Study On Their Electrocatalytic Properties

Recently, direct formic acid fuel cell (DFAFC) has attracted considerable attention due to its many advantages. However, DFAFC has two major shortcomings that limit its lifespan and performance:(i) the poor electrocatalytic stability of the carbon supported Pd (Pd/C) catalyst and (ii) rapid decomposition of formic acid over the Pd/C catalyst.In this thesis, two major shortcomings are combined to investigate. The following four methods are used to improve the electrocatalytic stability of the Pd/C catalyst and inhibit the decomposition of formic acid over the Pd/C catalyst:1. Improvement and Mechanism of Electrocatalytic Performance of Pd-Ni/C Anodic Catalyst in Direct Formic Acid Fuel CellOne problem of carbon supported Pd (Pd/C) anodic catalyst in direct formic acid fuel cell (DFAFC) is the poor electrocatalytic stability. Thus, the carbon supported Pd-Ni (Pd-Ni/C) catalyst was successfully synthesized via the high-temperature calcination and chemical etching. It was found that the electrocatalytic performance of the Pd-Ni/C catalyst for formic acid oxidation is much better than that of the Pd/C catalyst. It is due to two reasons. One is that the Pd-Ni/C catalyst prepared possesses the high alloy extent because the Pd based catalysts with high alloy extent possess usually the high electrocatalytic performance. Another is that the Pd-Ni/C catalyst can inhibit the decomposition of formic acid. Therefore, the Pd-Ni/C catalyst could be significantly protected from CO poisoning, leading to the excellent electrocatalytic stability.2. Synthesis and Electrocatalytic Properties of PdSb Network NanostructuresIn this work, we conveniently synthesize the networks-like palladium-antimony intermetallic nanoassemblies (PdSb INAs) by hydro-thermal method. The morphology, structure, size and composition of the PdSb INAs are characterized by transmission electron microscopy (TEM), energy dispersive spectrum (EDS), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Cyclic voltammetry, chronoamperometry and CO-stripping voltammetry tests demonstrate the PdSb INAs have higher electrocatalytic activity, better electrochemical stability, and higher resistance to CO poisoning over the commercial Pd nanoparticles for the formic acid oxidation (FAO) owing to their unique3D structure and intermetallic property.3. Synthesis and Electrocatalytic Properties of Dendritic Palladium NanostructuresIn this work, palladium dendrituc nanocrystals(DNs) have been synthesized by mixing an aqueous solution of cetyltrimethylammonium bromide (CTAB) surfactant, Na2PdCl4, Nickel acetate, and ascorbic acid at30℃for2h and60℃for1.5h. Addition of a small amount of Nickel ion source is critical to the formation of these dendritic nanocystals. The morphology, structure, size and composition of the Pd DNs are characterized by transmission electron microscopy (TEM), energy dispersive spectrum (EDS), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Cyclic voltammetry, chronoamperometry and CO-stripping voltammetry tests demonstrate the Pd DNs have higher electrocatalytic activity, better electrochemical stability, and higher resistance to CO poisoning over commercial Pd nanoparticles for the formic acid oxidation (FAO) owing to their unique dendrituc structure.