Abstract
In this work, graphitized ordered mesoporous carbons (gCMK-3) were employed as support for Pt and Pt–Ru nanoparticles synthesized by different reduction methods. The catalysts displayed metal contents and Pt:Ru atomic ratios close to 20 wt % and 1:1, respectively. A comparison of the physical parameters of Pt and Pt–Ru catalysts demonstrated that Ru enters into the Pt crystal structure, with well-dispersed nanoparticles on the carbon support. The Pt catalysts exhibited similar surface oxide composition, whereas a variable content of surface Pt and Ru oxides was found for the Pt–Ru catalysts. As expected, the Pt–Ru catalysts showed low CO oxidation onset and peak potentials, which were attributed to the high relative abundances of both metallic Pt and Ru oxides. All the studied catalysts exhibited higher maximum current densities than those observed for the commercial Pt and Pt–Ru catalysts, although the current–time curves at 0.6 V vs. reversible hydrogen electrode (RHE) demonstrated a slightly higher stationary current density in the case of the Pt/C commercial catalyst compared with Pt nanoparticles supported on gCMK-3s. However, the stationary currents obtained from the Pt–Ru/gCMK-3 catalysts surpassed those of the commercial Pt–Ru material, suggesting the suitability of the prepared catalysts as anodes for these devices.
Highlights
A quite interesting carbon material used as support for electrodes in direct methanol fuel cells (DMFCs) is the ordered mesoporous carbon (OMC)
This material is synthesized by nanocasting using a silica template, which is impregnated with a carbon-based resin that, after carbonization and silica removal, results in an OMC with a 3D interconnected porous structure, high surface area, and rich content of mesopores [1], which promote the formation of uniformly distributed nanoparticles on the carbon surface [2]
For the Pt catalysts, the smallest crystallite sizes were obtained for the FAM method and in agreement with that reported by Calderón et al for Pt–Ru catalysts supported on carbon nanofibers the largest ones for the EG, whereas the opposite was observed for the Pt–Ru materials
Summary
A quite interesting carbon material used as support for electrodes in direct methanol fuel cells (DMFCs) is the ordered mesoporous carbon (OMC). The relatively low temperatures employed during the carbonization stage seem to be the cause for the poor formation of extensive graphite layers [7,8] To avoid this drawback, graphitization of OMCs has been suggested by means of different procedures, such as the use of aromatic and polyaromatic hydrocarbons as carbon precursors during the silica template impregnation, as they can produce more graphitic domains after carbonization. The current densities associated with the oxidation of formic acid on these catalysts were higher than those observed on a Pd catalyst supported on carbon black [15] Regarding their use as cathode supports, Rivera et al. The activity of Pt and Pt–Ru catalysts supported on different graphitized ordered mesoporous carbon (gCMK-3) was studied in order to determine their behavior toward the CO and methanol electro-oxidation. The gCMK-3-supported catalysts displayed higher CO tolerance and improved methanol oxidation current densities than those observed for commercial Pt and Pt–Ru catalysts supported on carbon black from E-TEK, which were used as reference to evaluate the results displayed for these catalysts
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