Influence of Sacrificial Reagents on the Photoelectrocatalytic Performance of Titanium Dioxide Nanotube Arrays for Hydrogen Production

Photoelectrochemical water splitting offers a synergistic method for producing hydrogen using solar energy and an external bias with no emissions. Since the water oxidation process is a limiting factor in the hydrogen production rate, the use of efficient hole scavengers is crucial for enhancing system performance. This study evaluated the performance of titanium dioxide nanotubes (TiO2 NTs) using different hole scavengers in comparison to sodium sulfate. All the evaluated hole scavengers achieved higher photocurrent densities than sodium sulfate with performance ordered as follows: glycerol > glucose > triethanolamine > methanol > sodium sulfite > ethanol >> sodium sulfate. Regarding the hydrogen production rate, glycerol achieved 0.292 mL cm(-2) h(-1), a value 32.5 times higher than that obtained with sodium sulfate (0.009 mL cm(-2) h(-1)). Structural characteristics, such as the presence of hydrogen atoms adjacent to alcohol groups (alpha-H), the carbon-to-oxygen atom ratio (C:O), solvent polarizability, and redox potential were fundamental for understanding the role of hole scavengers. These findings validate the enhancement of the photoelectrocatalytic process by hole scavengers, supported by the thermodynamically favorable electron transfers facilitated by organic molecules with higher polarization, a low C:O ratio, and rich presence of alpha-H.