Solar photocatalytic and electrokinetic studies of TiO2/Ag nanoparticle suspensions

• TiO2 nanoparticles induce efficient solar photodegradation of Rhodamine B in water.
• Adding Ag powder substantially increases the photocatalytic efficiency of TiO2.
• Electrophoresis yields the type of particle contact in nanocomposite suspensions.
• Zeta potential-versus-pH is virtually the same for TiO2 and TiO2/Ag suspensions.
• TiO2 particles are permanently attached to Ag particles in the TiO2/Ag suspension.

Composites of TiO2 and Ag nanoparticles were used to study photodegradation of aqueous Rhodamine B under natural sunlight exposure. The addition of Ag powder resulted in a ∼45% increase of the photocatalytic activity of TiO2 after 30 min, which is attributed to the suppression of the photo-generated electron–hole pair recombination. Electrokinetic studies on TiO2, Ag, and TiO2/Ag aqueous solutions address the question of how the electron transfer occurs. It was found that the TiO2 and TiO2/Ag zeta potential versus pH behavior is virtually identical which suggests that the Ag particles are encapsulated by the TiO2 particles, allowing the electron transfer across the ‘static’ semiconductor–metal interface.

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