MANIFESTATION OF PHOTOCATALYSIS PROCESS VARIABLES IN A TITANIUM DIOXIDE-BASED SLURRY PHOTOELECTROCHEMICAL CELL

This paper examines how variables that influence photocatalytic events at ultraviolet (UV)-irradiated TiO2 particles manifest in the transie nt response from a slurry photoelectrochemical (PEC) cell. These inclu de the nature of the ambient gas, electrolyte pH and composition, and the presence of hole accepters in the electrolyte. Unlike the composit e photocurrent response observed in previous studies on TiO2-based slu rry PEC cells, the photoresponse was almost exclusively anodic under t he conditions extant in this work. The highest photoresponse was obtai ned in neutral electrolytes. Both O-2 and Cl- exerted a complex effect on the photoresponse, depending on the magnitude of the collector-ele ctrode potential. Pulsed photoexcitation of the TiO2 particles enables decoupling of processes with variant time constants in the slurry PEC cell, such as O-2 adsorption on TiO2, adsorption of TiO2 particles on the collector-electrode surface, and mass transport of TiO2 particles to the collector electrode. Finally, the influence of three types of environmental pollutants: viz., organic (formaldehyde), inorganic [As (III)], and biological (Escherichia coli), on the slurry cell photores ponse, is discussed.