TiO[sub 2]-Phosphotungstic Acid Photocatalysis Systems with an Energy Storage Ability

Abstract

Phosphotungstic acid (PWA) was utilized as the reductive energy storagesubstance instead of conventional WO3 for the fabrication of an energystorage photocatalyst, which retains its reducing ability even afterlight irradiation. In the case where a PWA film was electrochemicallycharged at 20.8 V vs. Ag/AgCl for 1 h in 3 wt% aqueous NaCl, it showedlonger self-discharge time than a WO3 film of the same thickness.Photoelectrochemical properties of the PWA and WO3 films coated withporous TiO2 were also studied. The PWA and WO3 films could be chargedunder UV light (1 mW/ cm(2)) for 1 h in 3 wt% aqueous NaCl. Althoughthe amount of charge accumulated in the PWA-TiO2 film was smaller thanthat in the WO3-TiO2 film, the self-discharge time of the former waslonger. Slower self-discharging process by O-2, which may beadvantageous for some applications, of the former is responsible forthese results. The PWA-TiO2 film showed relatively good durability afterseveral cycles. (C) 2003 The Electrochemical Society.