Carbon nanotubes (CNT) supported platinum-ruthenium (Pt-Ru) catalysts were prepared by impregnation-reduction using an ethanolic solution of H2PtCl6 and RuCl3. The effect of reduction temperatures on particle size, surface area and their relationship to the electrocatalytic activity for methanol oxidation were investigated. Thermogravimetric analysis, scanning electron microscopy, transmission electron microscopy, X-ray diffraction (XRD) as well as X-ray photoelectron spectroscopy (XPS) were used for the catalyst characterization. XRD analysis showed that the PtRu/ CNT catalysts possibly consist of separate Pt and Ru phases. XPS analysis showed that the catalysts contain hydrous ruthenium oxide in addition to Pt and Ru metal and oxide species. The electrocatalytic activities of the catalysts were investigated in half-cell experiments using cyclic voltammetry, CO stripping voltammetry, chronoamperometry, and impedance spectroscopy. The results showed that the catalyst reduced at a temperature of 350 degrees C had the largest electrochemical surface area, lowest charge transfer resistance and the highest electrocatalytic activity for methanol oxidation. The superior catalytic activity is discussed based on the presence of appropriate amount of hydrated Ru oxide.
Electrochemical reduction of carbon dioxide (CO 2 ) was performed on zinc-deposited copper (Cu/Zn) electrodes, and the faradaic efficiency of this system toward methane, ethane, and hydrogen was evaluated. Hierarchically structured Zn was electrodeposited on a Cu substrate under constant voltage in a varying bath concentration of Zn to yield low-and high-concentration deposits, represented as Cu/Zn-A and Cu/Zn-B, respectively. The prepared materials were characterized by X-ray diffraction, scanning electron microscopy, and X-ray photoelectron spectroscopy. The reduction of CO 2 was performed with the Cu/Zn electrodes in an H-type cell, and the results obtained were compared with those from bare Cu and Zn electrodes, revealing that a high deposit of Zn on Cu (Cu/Zn-B) shows greater conversion efficiency than does a low Zn deposit (Cu/Zn-A) and the maximum faradaic efficiency of methane follows the order Cu/Zn-B (52%) > Cu (23%) > Zn (7%). Moreover, the efficiency of hydrogen formation is suppressed on Cu/Zn-B (8%) compared to bare Cu (68%) in the potential range studied. The results suggest that depositing Zn on Cu favors a protonation reaction, which results in higher C 1 product formation on a Cu/Zn-B electrode.
Silver catalysts with three different metal loadings e.g. 10, 20 and 40 wt% were synthesised on carbon nanotubes (Ag/CNT) support by glycerol reduction method. The catalysts were characterised by X‐ray diffraction, electron microscopy and thermogravimetric analysis. The average crystalline size of Ag was found between 10 and 16 nm for the metal loading from 10 to 40 wt%. The catalytic activity towards oxygen reduction reaction (ORR) in alkaline solution was studied for the Ag/CNT catalysts in terms of mass activity as well as specific activity. Cyclic voltammetry and rotating disc electrode studies showed higher current density for 40 wt% Ag/CNT catalyst, which maintained suitable durability in potential sweeping cycling in comparison to 10 and 20 wt% Ag/CNT. The fuel cell studies of the synthesized catalysts were conducted using an anion exchange membrane, and all the three Ag/CNT catalysts showed open circuit voltage above 1 V with 40 wt% Ag/CNT gave the highest peak power density of 26.1 mW cm−2 at room temperature, in good agreement with the kinetic data obtained from the half‐cell studies.
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