Experimental testing of a novel photo-reactor for photocatalytic soap foams

A three-component homogeneous photocatalytic system for hydrogen evolution was evaluated and optimized in a foam-based photoreactor developed within the SoFiA project. The setup consisted of a molecular photosensitizer (Ru(bpy)_3^(2+)), a cobalt-based hydrogen evolution catalyst (cobaloxime), and sodium ascorbate as sacrificial electron donor, later supplemented with tris(2-carboxyethyl)phosphine (TCEP) acting as electron-relay. The reactor operation was re-established through the development of a fully reproducible methodology including surfactant optimization (Triton X-100 concentration up to 20×CMC), buffer selection, and systematic control of light exposure and gas removal. Real-time hydrogen detection was carried out using a needle-type Clark electrode, and quantitative data were processed through OriginLab. Although no measurable hydrogen evolution was observed under any of the tested conditions, this work identified key physicochemical bottlenecks, including limited solubility of the C_10-alkyl-modified cobaloxime, which prevented its effective use in interfacial catalysis, while the corresponding Ru-photosensitizer derivative was successfully solubilized. Overall, the study provides a validated experimental workflow and essential design criteria for further development of interfacial photocatalysis in soap-foam environments.