| Summary: | Photocatalytic hydrogen production via water splitting using a noble metal on a TiO<sub>2</sub> is a technology that has developed rapidly over the past few years. Specifically, palladium doped TiO<sub>2 </sub>irradiated with near-UV or alternatively with visible light has shown promising results. With this end in mind, strategically designed experiments were developed in the Photo-CREC Water-II (PCW-II) Reactor using a 0.25 wt% Pd-TiO<sub>2</sub> under near-UV and visible light, and ethanol as an organic scavenger. Acetaldehyde, carbon monoxide, carbon dioxide, methane, ethane, ethylene, and hydrogen peroxide together with hydrogen were the main chemical species observed. A Langmuir adsorption isotherm was also established for hydrogen peroxide. On this basis, it is shown that pH variations, hydrogen peroxide formation/adsorption, and the production of various redox chemical species provide an excellent carbon element balance, as well as OH<sup>•</sup> and H<sup>•</sup> radicals balances. Under near-UV irradiation, 108 cm<sup>3</sup> STP of H<sub>2</sub> is produced after 6 h, reaching an 99.8% elemental carbon balance and 98.2% OH<sup>•</sup> and H<sup>•</sup> and radical balance. It is also proven that a similar reaction network can be considered adequate for the photoreduced Pd-TiO<sub>2</sub> photocatalyst yielding 29 cm<sup>3</sup> STP of H<sub>2</sub> with 97.5% carbon and the 99.2% OH<sup>•</sup>–H<sup>•</sup> radical balance closures. It is shown on this basis that a proposed “series-parallel” reaction network describes the water splitting reaction using the mesoporous Pd-TiO<sub>2</sub> and ethanol as organic scavenger.
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