Natalia Soledad Veizaga

The development of advanced anode electrocatalysts for direct ethanol fuel cells (DEFCs) faces key challenges related to the complete oxidation of ethanol, particularly the cleavage of the CC bond. This study investigates the impact of chemical functionalization (using HNO ₃ , H ₂ O ₂ , and urea) of mesoporous carbon (MC) supports on the performance of Pt and PtRe catalysts. Functionalization modifies the carbon structure, introducing nanowindows or causing wall degradation, altering conductivity and surface chemistry without significantly affecting particle size. Catalysts synthesized by the polyol method are characterized structurally, texturally, and electrochemically. The results demonstrate that Re addition enhances ethanol electrooxidation through synergistic effects with Pt, reducing onset potentials and increasing electrochemically active surface areas, particularly at an optimal Re loading of 3 wt%. Functionalized supports, especially MC‐HNO ₃ , further improve catalyst dispersion and electrochemical performance. Prototype fuel cell tests confirm these trends, highlighting the importance of metal synergy and carbon surface functionalization.

Ru catalysts supported on activated carbon obtained by hydrothermal treatment of rice husk were evaluated in the hydrogenation reaction of levulinic acid to γ-valerolactone. The hydrothermally treated carbon was characterized by nitrogen physisorption, elemental analysis, and thermogravimetric analysis, and the catalysts were characterized by FTIR spectroscopy, X-ray photoelectron spectroscopy, temperature-programmed reduction, and temperature-programmed desorption of pyridine (acidic properties). Prior to the reaction, the catalysts were reduced at different temperatures in the range of 100–350 °C to evaluate the effect of the reduction temperature on the performance in the hydrogenation of levulinic acid. The reaction was carried out in a batch reactor at 70 °C and 1.5 MPa. The results of conversion and selectivity to γ-valerolactone showed that the catalyst with the best performance was the sample reduced at 200 °C. After 2 h of reaction, a γ-valerolactone yield of 74% was achieved. This catalyst presented the lowest acidity value, and the ruthenium-containing phase consisted mainly of RuO₂, with a small portion of Ru⁰. The solid catalyst can be recovered and successfully reused for three runs with the GVL yield at 56%.

Multiwalled carbon nanotubes and Vulcan carbon were functionalized with a 30 %v/v hydrogen peroxide solution and employed as supports for Pt and PtSn catalysts prepared by the polyol method. PtSn catalysts with a Pt loading of 20 wt.% and a Pt : Sn atomic ratio equal to 3 : 1 were evaluated in the ethanol electrooxidation reaction. The effects of the oxidizing treatment on the surface area and the surface chemical nature were analyzed through N₂ adsorption, isoelectric point, and temperature‐programmed desorption measurements. Results showed that the H₂O₂ treatment affects the surface area of the carbons to a great extent. Characterization results indicated that the performance of the electrocatalysts strongly depends both on the presence of Sn and on the support functionalization. PtSn/CNT−H₂O₂ electrocatalyst displays a high electrochemical surface area and enhanced catalytic activity for ethanol oxidation in comparison to other catalysts in the present study.

Several bimetallic PtSn catalysts supported on multiwalled carbon nanotubes for ethanol electro‐oxidation were prepared by conventional impregnation‐reduction method. The Pt loading was kept at 20 wt.% and Pt:Sn atomic ratios of 5:1, 3:1, and 1:1 were selected. The catalysts were structurally characterized by temperature programmed reduction, X‐ray diffraction, X‐ray photoelectron spectroscopy, H₂ chemisorption, cyclohexane dehydrogenation reaction, and transmission electron microscopy. The electrochemical characterization of the electrocatalytic materials was carried out in acid medium by cyclic voltammetry, linear sweep voltammetry, chronoamperometry, and CO stripping techniques. Among the different stoichiometries tested, the Pt(20)Sn(12.17)/CNT catalyst exhibited the highest electrocatalytic activity for ethanol oxidation reaction, with mass current density of 189.5 mA mgPt⁻¹ at 796 mV (vs. Ag/AgCl).

Monometallic Pt catalysts (17%wt) were prepared over Vulcan carbon (VC) and multiwall carbon nanotubes (NT). These supports were functionalized with citric or nitric acid. The characteristics of the different functionalized and non-functionalized supports were analyzed to determine the influence of the functional groups over the electrocatalytic behavior of the Pt monometallic catalyst. The functionalization treatment with nitric acid increases the concentration of strong and weak functional groups, whereas citric acid promotes the formation of acid groups with intermediate acidic strength. Catalysts prepared by conventional impregnation (CI) and supported on functionalized VC and NT display much higher electrochemical active areas than those supported on the corresponding non-functionalized carbons. Both the decrease of the metallic particle sizes and the changes in the metal-support interaction due to the presence of the functional groups would lead to a better electrochemical behavior.