A Comparative Study of the Catalytic Performance of Pt-Based Bi and Trimetallic Nanocatalysts Towards Methanol, Ethanol, Ethylene Glycol, and Glycerol Electro-Oxidation.

Carbon-supported platinum is used as an anode and cathode electrocatalyst in low-temperature fuel cells fueled with low-molecular-weight alcohols in fuel cells. The cost of Pt and its low activity towards the complete oxidation of these fuels are significant barriers to the widespread use of these types of fuel cells. Here, we report on the development of PtRhNi nanocatalysts supported on carbon made using a reduction chemistry method with different atomic rates. The catalytic activity of the developed catalysts towards the electro-oxidation of methanol, ethanol, ethylene glycol, and glycerol in acidic media was studied. The obtained catalysts performances were compared with both commercial Pt/C and binary Pt75Ni25/C catalyst. The nanostructures were characterized, employing inductively coupled plasma optical emission spectrometer, X-ray diffraction, scanning transmission electron microscopy, and energy-dispersive X-ray spectroscopy. The binary catalyst presents a mean particle size of around 2 nm. Whereas the ternary catalysts present particles of similar size and with some large alloy and core-shell structures. The alcohol oxidation onset potential and the current density measured after 3600 s of chronoamperometry were used to classify the catalytic activity of the catalysts towards the oxidation of methanol, ethanol, ethylene glycol, and glycerol. The best PtRhNi/C catalyst composition (i.e., Pt43Rh43Ni14/C) presented the highest activity for alcohols oxidation compared with all catalysts studied, indicating the proper tuning composition influence in the catalytic activity. The enhanced activity of Pt43Rh43Ni14/C can be attributed to the synergic effect of trimetallic compounds, Pt, Ni, and Rh.

The Effect of Pt Loading on Catalytic Activity of Pb0.25@Ptx/C Nanocomposites Toward Ethanol Oxidation.

Here, we study the influence of the Pt loading and the particle size of Pb0.25@Ptx/C catalysts on their specific activity toward ethanol oxidation in acid media. High angle annular dark field-scanning transmission electron microscopy and electron energy loss spectroscopy data indicate the formation of Pb0.25@Ptx/C core-shell structures, which are well dispersed on carbon support, with spherical shapes and small particle sizes (2.9-6.6 nm). Cyclic voltammetry experiments confirm characteristic profiles of polycrystalline Pt for Pb0.25@Ptx/C structures. The specific activity of the catalysts toward ethanol oxidation reaction greatly depends on the Pt content on Pb core, and consequently, depends on the size of the nanoparticles. The optimum activity occurs with the lowest Pt load in the shell and smaller particle size. Enhancements in specific activity result from the higher number of nanoparticles available for the ethanol oxidation reaction and the tensile strain effect of Pt atoms on the surface expanded in Pb0.25@Pt0.75/C. The lower activity observed for the catalysts with loads of 35 and 50% wt. (Pb0.25@Pt1.5 and Pb0.25@Pt2.25/C, respectively) in comparison to Pt/C, could be explain by the larger particle sizes obtained at these catalysts. Moreover, the Pb0.25@Pt0.75/C catalyst has high electrochemical stability and should be more stable in direct ethanol fuel cells systems than monolithic Pt catalysts. This is because the Pt shell in Pb0.25@Pt0.75/C exhibits lower chemical potential (p < 0) than at Pt/C and at the other core-shell catalysts studied; thus, reducing its tendency to dissolve. The developed core-shell nanostructure is thus a potential candidate as high-performance anode catalyst for application in direct ethanol fuel cells.