Liquid Crystal Templates Synthesis Of Palladium/Polyaniline Nanocomposites And Its Electrocatalytic Behavior

Pd/PANI nanocomposites were synthesized in lyotropic liquid crystal templates made with quaternary system (brine/cyclohexane/surfactant/cosurfactant) via photothermally assisted solution approach, using visible light from a commercial incandescent lamp as light source. Samples were characterized by FESEM、HRTEM、 SAED、XRD、FT-IR、UV-vis and EDS to study the effect of different polymerization conditions on Pd/PANI nanocomposites. Electrocatalytic properties of the Pd/PANI nanocomposites modified glassy carbon electrode (Pd/PANI/GCE) for ethanol oxidation and methane oxidation had been also investigated by electrochemical process.(1) Pd/PANI nanocomposites were synthesized in lyotropic liquid crystal templates via photothermally assisted solution approach. The effects of the molar ratio of palladium chloride (PdCl2) and An and the power density on the structure and morphology of Pd/PANI nanocomposites were investigated. When the molar ratio of PdCl2 and An is 1:8 and the power density is 31.75×102μw/cm, monodisperse sea anemone-like Pd/PANI nanocomposites were synthesized in liquid crystal templates while the average diameter is 320 nm and the Pd nanoparticles with particle size of (24±1) nm.(2) The electrochemical behaviors of Pd/PANI nanocomposites were investigated. When the molar ratio of PdCl2 and An is 1:8 and the power density is 31.75 ×10μw/cm, sea anemone-like Pd/PANI nanocomposites were synthesized with the best electrocatalytic activity to ethanol. The cyclic voltammetry curve showed that, the first oxidation peak appeared at -0.475V during forward scanning process and the second oxidation peak appeared at -0.308V during the regression scanning process,corresponds to a high mass electrochemical activity of 549A g-1. It showed that the Pd/PANI nanocomposites as anode catalysts exihibits the excellent electrocatalytic activity for the ethanol oxidation. The ratio of If/Ir was 1.93, which indicated that Pd/PANI has a higher electrocatalytic activity for ethanol oxidation and better effect decreasing CO poison. The Chronoamperogram showed that the observed decay of catalytic activity is significantly lower compared with that of commercial catalysts based on 5wt% Pd activated carbon powder and Vulcan XC-72 containing 20wt% Pd, which retained almost 12.9% after 4000 s and 24% after 4000 s of their original activity, suggesting that Pd/PANI nanocomposites exihibits with stable electrocatalytic activity for the ethanol oxidation in alkaline solution. Therefore, Pd/PANI nanocomposite is a promising anode catalyst for alkaline fuel cells.(3) The electrochemical behaviors of Pd/PANI nanocomposites to methane were investigated. When the molar ratio of PdCl2 and An is 1:8 and the power density is 31.75×102μw/cm2, sea anemone-like Pd/PANI nanocomposites were synthesized with the best electrocatalytic activity to methane. The cyclic voltammetry curve showed that a obvious reduction peak appeared at the peak of -0.022V, and a strong and extensive oxidation peak appeared at the peak of 0.478V. With the increase of scanning rate, the Pd/PANI/GCE has more obvious electrocatalytic effect of methane in 0.50mol/L sulfuric acid solution. It indicated that Pd/PANI has a higher electrocatalytic activity for methane oxidation and better effect decreasing CO poison. The Chronoamperogram showed that, Pd/PANI nanocomposites is renewable resources with high sensitivity and high electrocatalytic activity for methane oxidation after six months storage.It shows that the Pd/PANI nanocomposite has a stable electrocatalytic activity for methane in acid solution.