Investigation of the photocatalytic activity of ZnO nanowires: Substrate effect and kinetics analysis

Abstract

The photocatalytic activity of substrate-supported ZnO nanowires is investigated with a focus on the substrate effect and the photodegradation kinetics. The employed NWs are grown on various substrates by thermal evaporation and a 50 M rhodamine B solution is used as the target solution. It is found that the photocatalytic activity is facilitated by using a conductive substrate and such a result can be reasonably attributed to the improvement of charge separation. The photodegradation is found to follow a zeroth-order kinetics at high concentrations and a first-order kinetics at low concentrations with a transition at around 10 M. The present observation is opposed to the commonly accepted first-order kinetics. Degradation constants of 0.58 M·min-1 for the zeroth-order and 0.028 min-1 for the first-order have been achieved. The first-order constant also compares favorably with reported values. © 2014 Jan-Hau Chang and Heh-Nan Lin.