Photocatalytic hydrogen production via water splitting using a noble metal on a TiO₂ is a technology that has developed rapidly over the past few years. Specifically, palladium doped TiO₂ 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-TiO₂ 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^• and H^• radicals balances. Under near-UV irradiation, 113 cm³ STP of H₂ is produced after 6 h, reaching an 99.8% elemental carbon balance and 99.2% OH^• and H^• and radical balance. It is also proven that a similar reaction network can be considered adequate for the photoreduced Pd-TiO₂ photocatalyst yielding 29 cm³ STP of H₂ with 95.4% carbon and the 97.5% OH^•–H^• 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-TiO₂ and ethanol as organic scavenger.