Since Pt is in situ photodeposited on the catalyst surface, after Ar bubbling a small volume from a 14 g L -1 H2PtCl6 aqueous solution was added by a 10-100 µL micropipette to the catalyst suspension (1 g L -1 ), corresponding to 3% w/w Pt. Each photoreactor was closed with sleeve stopper septa and irradiated, as described in the following, achieving simultaneous Pt deposition and H2 production. Irradiation was performed under simulated sola light (1500 W Xenon lamp, 300-800 nm) using a Solar Box 1500e (CO.FO.ME.GRA S.r.l., Milan, Italy) set at a power factor 500 W m -2 , and equipped with UV outdoor filter made of IR-treated soda lime glass. Triplicate photoproduction experiments were done on all samples. The headspace evolved gas was quantified by gas chromatography coupled with thermal conductivity detection (GC-TCD), as detailed in previous work. The results obtained in terms of H2 evolution rate (HER) are expressed in the paper as µmol of gas per gram of catalyst per hour (µmole g -1 h -1 ). The kinetics of H2 formation, studied for the best performing composite through duplicate experiments, is reported in Figure . The photon flux measured as previously reported, was 1.53  10 -7 photons moles s -1 . The apparent quantum yield (AQY), calculated as the percent ratio H2 moles/incident photons moles was 2.3% for the composite giving the highest H2 evolution. Nitrogen Photofixation Experiments N2 photofixation experiments were conducted in tridistilled water containing 10% (v/v) methanol (Aldrich, ≥99.9%) irradiated in Pyrex glass container (250 mL capacity, 100 mL sample). After addition of the catalyst (0.5 g L -1 ), the sample suspension was deoxygenated by N2 bubbling (45 min) to obtain a saturated solution and then irradiated under magnetic stirring for 3 hours maintaining the temperature at 15 °C. For the experiments involving use of 1 wt % Pt co-catalyst, the same Chloroplatinic acid (H2PtCl6, 38% Pt basis) was added as precursor for metallic Pt (Aldrich).