Search

Abstract: Here we report on an advanced nanoscale catalyst system of PtPd nanodendrites and their electrochemical catalytic activity toward the oxidation of methanol. The Pt and Pd based nanostructured materials with different compositions, Pt, PtPd(25%), PtPd(50%), PtPd(75%) and Pd, were prepared using a facile hydrothermal method. These catalysts were tested for efficacy in the oxidation of methanol using cyclic voltammetry and chronoamperometry, as well as in situ electrochemical infrared (IR) spectroscopy. In terms of methanol oxidation, the PtPd(50%) nanodendrite catalyst was found to have the highest electrocatalytic activity over its counterparts as well as pure Pt and Pd. With the increase of the Pd component, the intensity of the CO peaks decreased and the CO band shifted to a lower wavenumber. The final product of methanol oxidation, CO2, was observed at the lowest potential (100mV) for the PtPd(50%) among the nanoporous Pt and PtPd nanodentrites investigated in this study, whereas no CO and CO2 peaks appeared in the IR spectra recorded for the nanoporous Pd. The enhanced Pt activity in the oxidation of methanol via the incorporation of Pd may be attributed to a synergistic catalytic effect. With a balance of 50:50 of Pt/Pd, not only are the maximum number of sites made available for the formation of the COads and the OHads species, but also those sites that are in closest proximity between the formed Pt–COads and Pd–OHads. These synergistic effects translate to a significant improvement in the electrochemical oxidation of methanol through the formation of PtPd(50%) nanodentrites. [Copyright &y& Elsevier]

Abstract: We report on the kinetics of photoelectrochemical oxidation of salicylic acid (SA) and salicylaldehyde (SH) on titanium dioxide nanotube arrays. The TiO2 nanotubes were prepared by the electrochemical oxidation of titanium substrates in a nonaqueous electrolyte (DMSO/HF). Scanning electron microscopy (SEM) was employed to examine the morphology of the formed nanotubes. Linear voltammetry was used to study the electrochemical and photoelectrochemical behavior of the synthesized TiO2 nanotube arrays. The photoelectrochemical oxidation of SA and SH on the TiO2 nanotubes was monitored by in situ UV–vis spectroscopy, showing that the kinetics of the photoelectrochemical oxidation of SA and SH follows pseudo first-order and that the rate constant of SH oxidation is 1.5 times larger than that of SA degradation. Quantum chemical calculations based on the DFT method were performed on SA and SH to address the large difference in kinetics. The relatively higher E LUMO − E HOMO makes SA more stable and thus more difficult to be oxidized photoelectrochemically. The impact of temperature and initial concentrations on the kinetics of SA and SH photoelectrochemical degradation was also investigated in the present work. [Copyright &y& Elsevier]