The Silver Chloride Photoanode in Photoelectrochemical Water Splitting

Abstract

Thin silver chloride layers evolve oxygen under UV/vis illumination in aqueous solution under appropriate conditions. AgCl deposited on a conducting support photocatalyzes the oxidation of water to O 2 in the presence of a small excess of silver ions in solution. The light sensitivity in the visible part of the spectrum is due to self-sensitization caused by reduced silver species. Anodic polarization reoxidizes the reduced silver species. Considerable improvement of sensitivity has been observed with AgBr sensitized AgCl photoanodes. To test its water splitting capability, the AgCl photoanode was combined with hydrogen-producing semiconductors, such as a platinized silicon solar cell and platinized p-GaInP 2 . AgCl layers were employed in the anodic part and the H 2 evolving semiconductors in the cathodic part of a photoelectrochemical cell for light-assisted water splitting. The AgCl electrodes were characterized with surface photovoltage spectroscopy (SPS), which identified the transition from the valence band to silver cluster levels and by in-situ UV/vis diffuse reflectance spectroscopy, which detects the reduced and reoxidized silver species.