Photocatalytic Hydrogen Production using Porous 3D Graphene-Based Aerogels Supporting Pt/TiO₂ Nanoparticles

Composites involving reduced graphene oxide (rGO) aerogels supporting Pt/TiO₂ nanoparticles were fabricated using a one-pot supercritical CO₂ gelling and drying method, followed by mild reduction under a N₂ atmosphere. Electron microscopy images and N₂ adsorption/desorption isotherms indicate the formation of 3D monolithic aerogels with a meso/macroporous morphology. A comprehensive evaluation of the synthesized photocatalyst was carried out with a focus on the target application: the photocatalytic production of H₂ from methanol in aqueous media. The reaction conditions (water/methanol ratio, catalyst concentration), together with the aerogel composition (Pt/TiO₂/rGO ratio) and architecture (size of the aerogel pieces), were the factors that varied in optimizing the process. These experimental parameters influenced the diffusion of the reactants/products inside the aerogel, the permeability of the porous structure, and the light-harvesting properties, all determined in this study towards maximizing H₂ production. Using methanol as the sacrificial agent, the measured H₂ production rate for the optimized system (18,800 µmol_H2h^-1g_NPs^-1) was remarkably higher than the values found in the literature for similar Pt/TiO₂/rGO catalysts and reaction media (2000-10,000 µmol_H2h^-1g_NPs^-1).