Tang Yawen

Electrocatalytic Performance of Pd Catalyst Supported on Macropore Carbon for Oxidation of Formic Acid

The electrocatalytic performances of a Vulcan XC-72 carbon black supported Pd (Pd/XC) catalyst and a macroporous carbon supported Pd (Pd/MC) catalyst for formic acid oxidation in a direct formic acid fuel cell were investigated and compared. This was carried out using X-ray energy dispersive spectroscopy (EDS), X-ray diffraction (XRD) spectroscopy, Raman spectroscopy, and electrochemical techniques. The cyclic voltammograms indicate that the main peak potentials for the oxidation of formic acid at the Pd/XC and Pd/MC catalyst electrodes are similar and they are located at about 0.15 V. However, the peak current density of the Pd/MC catalyst electrode is about 30% larger than that of the Pd/XC catalyst electrode. The chronoamperometric curves indicate that the peak current density at the Pd/MC catalyst electrode at 6000 s is about 38% larger than that at the Pd/XC catalyst electrode. These results show that the electrocatalytic activity and stability of the Pd/MC catalyst for the oxidation of formic acid are better than those of the Pd/XC catalyst. Because the average size and relative crystallinity of the Pd particles in the two catalysts are similar, the reason for the better electrocatalytic performance of the Pd/MC catalyst could be only attributed to its larger pore diameter and higher conductivity because of its high extent of MC graphitization.

Synthesis of spherical porous Pd nanoparticle superstructure and its catalytic oxidation of formic acid

Spherical porous Pd nanoparticle superstructures with the diameter in the range of 30-50 nm were obtained by the reaction of PdCl42- with hydrazine using hexadecylpyridinium chloride as a structure-directing agent in the mixed acetone/water solution. It was found that hexadecylpyridinium chloride had significant influence on the formation of the spherical porous Pd nanoparticle superstructure. Only solid spherical structure was formed in the absence of the surfactant. In addition, acetone had an effect on the size of the micelles modified. The electrocatalytic activity of the spherical porous Pd nanoparticle superstructure electrode for the formic acid oxidation in 0.5 mol/L H2SO4+0.5 mol/L HCOOH was also investigated. The results displayed that electrocatalytic activity and stability of the spherical porous Pd nanoparticle superstructure catalyst were better than that of the solid Pd catalyst.

Preparation of Carbon Supported Ir-Co Catalyst and Its Electrocatalytic Performance for Ammonia Oxidation

The Ir-Co/C catalyst was prepared via a liquid phase reduction method.X-ray diffraction(XRD) and transmission electron microscope(TEM) results indicated that Co atoms enter the crystal lattice of Ir and form the Ir-Co alloy as evidenced by the lattice constriction of Ir and the aggregation of Ir particles could be suppressed.The electrochemical investigation illustrated that comparing with the Ir/C catalyst,the onset potential of the NH3 oxidation is negatively shifted about 100 mV,the peak current density is increased about 100% and the electrocatalytic stability is also increased at the Ir-Co/C catalyst.In addition,the sensitivity and the detection limit of NH3 are decreased at the Ir-Co/C catalyst.The results illustrate that the electrocatalytic performance of the Ir-Co/C catalyst for the NH3 oxidation is obviously better than that of the Ir/C catalyst.Thus,the Ir-Co/C catalyst has a potential application in the electrochemical NH3 sensor.

Effect of Atomic Ratio of Pd and Pt in Carbon supported Pd-Pt Catalyst on its Cathodic Performance in Direct Methanol Fuel Cell

The electrocatalytic performance for the oxygen reduction and the methanol tolerance ability of the Pd-Pt/C catalysts with different atom ratios of Pd and Pt was investigated.It is found that when the atom ratio of Pd and Pt is increased from 20∶0 to 17∶3,the electrocatalytic performance of the Pd-Pt/C catalyst for the oxygen reduction is increased.Furthermore,all the Pd-Pt/C catalysts with the atom ratios in the range of 20∶0~17∶3 have no electrocatalytic activity for the methanol oxidation and thus possess the excellent methanol tolerance ability.When the atom ratio is increased to 16∶4,the electrocatalytic performance of the Pd-Pt/C catalyst for the oxygen reduction is still increased,but the methanol tolerance ability is decreased.Thus,the Pd-Pt/C catalyst with 17∶3 atom ratio possesses an excellent electrocatalytic activity for oxygen reduction and methanol tolerance ability.Therefore,it can be used as the cathodic catalyst in direct methanol fuel cell(DMFC).

Electrocatalytic Performance of Carbon-Supported Pt-P Catalyst for Oxygen Reduction

The carbon-supported Pt-P(Pt-P/C) catalyst(m(Pt):m(P) = 5:1) was prepared with NaH2PO2 reduction method.The X-ray diffraction results indicate that the 2θ values of the Pt diffraction peaks of the Pt-P/C catalyst are slightly greater than those of the Pt/C catalyst,illustrating that P has entered into the crystal lattice of Pt and forms the Pt-P alloy.The electrochemical measurements demonstrated that the electrocatalytic performance of the Pt-P/C catalyst for the oxygen reduction is better than that of the commercial E-TEK Pt/C catalyst with 40 mV positive shift of reduction potential,which may be attributed to the P action because the average size and the relative crystallinity of the Pt-P particles in the Pt-P/C catalyst are similar to those in Pt/C catalyst.