Kinetic Modeling and Quantum Yields: Hydrogen Production via Pd-TiO2 Photocatalytic Water Splitting under Near-UV and Visible Light

A palladium (Pd) doped mesoporous titanium dioxide (TiO2) photocatalyst was used to produce hydrogen (H-2) via water splitting under both near-UV and visible light. Experiments were carried out in the Photo-CREC Water-II Reactor (PCW-II) using a 0.25 wt% Pd-TiO2 photocatalyst, initial pH = 4 and 2.0 v/v% ethanol, as an organic scavenger. After 6 h of near-UV irradiation, this photocatalyst yielded 113 cm(3) STP of hydrogen (H-2). Furthermore, after 1 h of near-UV photoreduction followed by 5 h of visible light, the 0.25 wt% Pd-TiO2 photocatalyst yielded 5.25 cm(3) STP of H-2. The same photocatalyst, photoreduced for 24 h under near-UV and subsequently exposed to 5 h of visible light, yielded 29 cm(3) STP of H-2. It was observed that the promoted redox reactions led to the production of hydrogen and by-products such as methane, ethane, ethylene, acetaldehyde, carbon monoxide, carbon dioxide and hydrogen peroxide. These redox reactions could be modeled using an in series-parallel reaction network and Langmuir Hinshelwood based kinetics. The proposed rate equations were validated using statistical analysis for the experimental data and calculated kinetic parameters. Furthermore, Quantum yields (QYH & BULL;%) based on the H-& BULL; produced were also established at promising levels: (a) 34.8% under near-UV light and 1.00 g L-1 photocatalyst concentration; (b) 8.8% under visible light and 0.15 g L-1. photocatalyst concentration following 24 h of near-UV.

Automated summary

A palladium-doped mesoporous titanium dioxide photocatalyst was used for hydrogen production via water splitting under both near-UV and visible light. The experiments showed that this photocatalyst could generate hydrogen gas under different conditions, along with several by-products. Additionally, the study modeled the photocatalytic reactions and analyzed the kinetics, validating the proposed rate equations.