Anode Catalysts Based On Palladium-silver-gold And Their Electrocatalytic Oxidation Of Alcohols

In order to solve the accelerated consumption of traditional fossil fuels and the ensuing environmental pollution problems,small organic molecules with high specific energy and high power density（such as alcohol,organic acid）are regarded as an ideal alternative to traditional fossil fuels.Direct alcohol fuel cells（DAFCs）hold the critical characteristics of high energy/power density at relatively low operating temperatures,low cost,and easy storage,which has attracted the attention of the energy market and research field.Platinum（Pt）is considered to be one of the best catalysts for DAFCs.However,its reserve is unable to meet the large amount request of the energy market,which limits its large-scale commercialization.Palladium,instead,has more abundant reserves,better cost performance,and better catalytic performance as well as better CO tolerance than Pt under the alkaline conditions.With the application of nanotechnology in the synthesis of catalysts,researchers have developed many efficient and stable Pd-based catalysts for DAFCs application.From the perspectives of catalyst preparation process,catalyst material components,and catalyst structure and morphology design,a series of Pd-based catalysts were prepared and their electrocatalytic performances toward the oxidation of methanol and ethanol in alkaline environment have been investigated.The main research contents in this dissertation are as follows:（1）Pd Au bimetallic nanoparticle catalyst（Pd Au@PANI-PSSA）coated with a conductive coating of polyaniline（PANI）modified by poly（4-styrenesulfonic acid）（PSSA）was prepared.The catalyst is a bayberry-like nanostructure formed by clusters of many nanoparticles.The unique structure increases the contact area with the reactants and improves the catalytic performance of the catalyst.The modified PANI coating further improves the charge transport performance of the catalyst,and the oxygen-containing functional groups in PSSA help to accelerate the release of active sites and improve the anti-toxicity of the catalyst.The prepared Pd₁Au_2.5@PANI-PSSA catalyst shows a normalized current density of 1598.2 m A mg_Pd^-1,and the active surface area of 102.65 m² g^-1,which is 3.0 and 2.7 times than that of 20%commercial Pd/C,respectively.（2）A method of adjusting the arrangement of atoms on the surface of the catalyst using chemical etching is designed to prepare a nano-cage catalyst with a porous structure.By controlling the reaction stoichiometric volume of the Pd（II）precursor,Ag nanocubes can be transformed into Ag Pd cage cubes with different pore sizes and metal compositions.This strategy controls the deposition of Pd atoms on the surface of the catalyst,and significantly improves the utilization of Pd.The introduction of Ag not only modifies the surface electronic structure of Pd through the interaction between metals,but also promotes the adsorption of-OH_ad and accelerates the oxidation removal of-CO_ad.（3）The second type of precursor etching was introduced on the basis of etching.In addition to the good stability of Au itself,its etching and deposition can bring more hollow and porous structures to provide the abundant catalytic active sites for the catalyst,which significantly improves the catalytic performance of the catalyst.The Ag-Au-Pd nano-cage catalyst prepared by a series of optimizations exhibits high current density and higher ECSA performance than commercial Pd black catalysts.This strategy of using etching as a synthesis method is expected to develop other similar hollow multi-metal nano-frame structures in electrocatalytic applications.