Electrocatalytic performance of Pt supported on functionalized and non-functionalized carbonaceous materials for ethanol electrooxidation toward hydrogen production

Abstract This study investigated Pt catalysts supported on Vulcan XC72 carbon (VXC72) and multi-walled carbon nanotubes (MWCNT), functionalized and non-functionalized with HNO 3 , for ethanol electrooxidation and hydrogen production in alkaline medium. The materials were synthesized by the thermal decomposition method of polymeric precursors and characterized by X-ray diffraction, Raman spectroscopy, Fourier-transform infrared spectroscopy, and transmission electron microscopy. Structural analyses confirmed the formation of metallic Pt with a face-centered cubic structure, while Raman and FTIR analyses indicated structural and surface modifications associated with support functionalization, including the presence of oxygen-containing surface groups. TEM analysis revealed predominantly spherical Pt nanoparticles distributed over the carbon supports, with Pt/VXC72_F exhibiting the smallest average particle size among the investigated electrocatalysts. Electrochemical performance was evaluated by cyclic voltammetry and chronoamperometry in 1.0 mol L⁻ 1 KOH and 1.0 mol L⁻ 1 KOH + 1.0 mol L⁻ 1 ethanol solutions. The effect of HNO 3 functionalization on the electrochemical response was support-dependent, with functionalized Vulcan XC72 exhibiting a more pronounced modification of the electrode/electrolyte interfacial response than MWCNT. Among the Pt-based electrocatalysts, Pt/VXC72_F exhibited the highest geometric current densities and the most negative onset potential for ethanol electrooxidation under the investigated conditions. Chronoamperometric measurements at − 0.10 V vs. Hg/HgO showed that Pt/VXC72_F maintained the highest current density at this specific applied potential. However, because this potential corresponds approximately to the first oxidation peak potential of Pt/VXC72_F while being more positive than the corresponding peak potentials of the other electrocatalysts, the chronoamperometric results cannot independently establish greater intrinsic stability or higher tolerance to poisoning intermediates. Hydrogen production experiments were performed in an H-type electrochemical cell at 3.0 V for 30 min. The Pt/VXC72_F system produced an average hydrogen volume of 16.3 mL, corresponding to an average hydrogen production flow rate of 0.54 ± 0.01 mL min⁻ 1 , whereas the Ni plate (blank) produced 9.76 mL and 0.32 ± 0.01 mL min⁻ 1 , respectively. The experimental hydrogen volumes corresponded to 97.3% and 93.4% of the theoretical values predicted by Faraday's law for Pt/VXC72_F and the Ni plate, respectively. However, because the hydrogen production experiments were conducted at different applied currents (0.08 A for Pt/VXC72_F and 0.05 A for the Ni plate), the higher hydrogen volume and production rate observed for Pt/VXC72_F cannot be attributed exclusively to its catalytic activity. Overall, the results demonstrate that the nature and functionalization of the carbon support influence the electrochemical behavior of Pt-based electrocatalysts. Under the investigated conditions, Pt/VXC72_F exhibited the highest geometric current densities and the most negative onset potential for ethanol electrooxidation, while the hydrogen production experiments yielded hydrogen volumes close to the theoretical values predicted by Faraday's law. These findings demonstrate the potential of functionalized Vulcan XC72 as a carbon support for Pt-based electrocatalysts in alkaline hydrogen production assisted by ethanol electrooxidation.