| Summary: | Composites involving reduced graphene oxide (rGO) aerogels supporting Pt/TiO<sub>2</sub> nanoparticles were fabricated using a one-pot supercritical CO<sub>2</sub> gelling and drying method, followed by mild reduction under a N<sub>2</sub> atmosphere. Electron microscopy images and N<sub>2</sub> 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 H<sub>2</sub> from methanol in aqueous media. The reaction conditions (water/methanol ratio, catalyst concentration), together with the aerogel composition (Pt/TiO<sub>2</sub>/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 H<sub>2</sub> production. Using methanol as the sacrificial agent, the measured H<sub>2</sub> production rate for the optimized system (18,800 µmol<sub>H2</sub>h<sup>−1</sup>g<sub>NPs</sub><sup>−1</sup>) was remarkably higher than the values found in the literature for similar Pt/TiO<sub>2</sub>/rGO catalysts and reaction media (2000–10,000 µmol<sub>H2</sub>h<sup>−1</sup>g<sub>NPs</sub><sup>−1</sup>).
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