The Electrocatalytic Performances Of Pd-hgalloy As Bifunctional Catalytic Materials For ORR And EOR

Hydrogen peroxide(H2O2)is one of the most commonly produced chemicals and widely used in wastewater treatmwent and pulp/paper bleaching as an pollution-free green oxidan.Recently environmentalists have been keen on construct the electrochemical cathodic reductuion process to realize the in-situ generated hydrogen peroxide.Direct alcohol fuel cells(DAFCs)are typical engrgy devices which use renewable and environment-friendly alcohols as liquid fuels and have broad application prospects.Pd-based multifunctional alloy were prepared and applied as theelectrocatalysts for ORR and EOR in the paper,which was a attempt to develop highly efficient catalytic materials for the specific industrial application and prospect.The main research contents and conclusions are as follows:(1)The Pd-Hg alloy with the morphology of bipyramidal lamella and particle size of 50 nm was also synthesized by simultaneous reduction method using PdC12 and Hg12 as mental precursors and ascorbic acid as reductant in the mixture organic solvents of ethanol-pyridine-DMF(v1:V2:V3 = 16:4:1)at constant temperature.Similarly,another kind of Pd-Hg alloy with particle sizes ranging from 50 nm to 200 nm was synthesized by simultaneous reduction method using Pd(PPh3)2C12 and HgI2 as mental precursors and ascorbic acid as reductant in the mixture organic solvents of ethanol-pyridine-DMF(v]:v2:V3= 16:4:1)at constant temperature.Morover,three kinds of Pd-Hg alloy with the particle sizes ranging from 10 nm to 20 nm was prepared by changing the composition and proportion of the mixture organic solvents and loaded in the Vulcan XC-72R as the HgPd/C catalysts while using Pd(PPh3)2C12 and HgI2 as mental precursors and ascorbic acid as reductant.(2)The crystal phases of Pd-Hg alloy is determined by the molar ratio of mental precursors.The crystal phase of the Pd-Hg alloy with the morphology of bipyramidal lamella is HgPd at the molar ratio of Pd/Hg =1/3 while the crystal phases are HgPd and Hg5Pd2 at the molar ratio of Pd/Hg = 1/6.The pathway of ORR catalyzed by the Pd-Hg alloy in acidic media was two-electron transfer at the selectivity of 70%while in alkaline media was four-electron transfer at the selectivity of 90%.Moreover,the electrocatalytic performances of the Pd-Hg alloy post-treated by 15 wt%dilute nitric acid are strengthened significantly in acidic and alkaline media as the molar ratio of Pd and Hg was changed.The Pd-Hg alloy with the morphology of granular is in the crystal phases of HgPd at the molar ratio of Pd/Hg = 1/3 while the crystal phase is Hg5Pd2 at with the molar ratio of Pd/Hg = 1/6.The Pd-Hg alloy with the crystal phases of HgPd or Hg5Pd2 are efficient electrocatalysts for ORR in alkaline media,which undergo the pathway of four-electron transfer at the selectivity of 95%.(3)The Pd-Hg alloy with the crystal phase of HgPd exhibits electrocatalytic performances in the oxidation of alcohols.The three kinds of HgPd/C catalysts exhibit better eletrocatalytic performances than commercial Pt/C and Pd/C catalysts in the oxidation of ethanol and ethylene glycol.The intermediate product and final product of HgPd/C catalysts for EORis aldehyde and acetate ion obtained by In situ FTIR spectra,respectively.