Enhanced Photocatalytic Decomposition of Gaseous Isopropyl Alcohol in a Polymer Electrolyte Cell

Wei-Ming Hou,Young Ku

doi:10.4209/aaqr.2012.10.0298

Abstract

Electrochemical enhancement of the photocatalytic decomposition of isopropyl alcohol in gas phase was carried out in a polymer electrolyte cell. An external electrical field was created in the gas-phase photocatalytic reaction due to the presence of solid electrolyte. The effects of bias potential, relative humidity, initial isopropyl alcohol concentration and UV light intensities were investigated for the photoelectrocatalytic process. Photoelectrocatalytic decomposition of isopropyl alcohol was observed to be less sensitive to humidity for experiments that applied a bias potential higher than 2.5 V. Electrical current densities of photoanode were highly correlated to the variations in bias potential, relative humidity level and UV light intensity, although independent of inlet isopropyl alcohol concentrations. Humidity had an ambiguous effect on the membrane conductivity of polymer electrolyte and photocatalytic decomposition rate of isopropyl alcohol with the application of bias potential. The experimental results also showed that the energy consumed in the photoelectrocatalytic process was much less than that needed by the photocatalytic process to achieve a similar level of isopropyl alcohol decomposition.

Highlights

Photocatalytic oxidation process using semiconductive materials is a promising advanced oxidation technology in the fields of water and air treatment because of the relatively mild reaction conditions required to achieve satisfactory decomposition of refractory pollutants
No isopropyl alcohol (IPA) decomposition was observed by electrolytic process for experiments conducted with applied bias less than 2 V; merely about 8% IPA was decomposed for experiments conducted with applied bias potentials of 2.5 or 3 V
IPA decomposition was increased by roughly 13% with applied bias potentials of 2.5 or 3 V for photoelectrocatalytic process

Summary

Introduction

Photocatalytic oxidation process using semiconductive materials is a promising advanced oxidation technology in the fields of water and air treatment because of the relatively mild reaction conditions required to achieve satisfactory decomposition of refractory pollutants. The rapid recombination between photogenerated electrons and holes seriously restricts the effectiveness of photocatalytic processes, resulting in low quantum yields for most photocatalytic reactions (Chen and Ku, 2007; Ku et al, 2010a). The bias-assisted photocatalytic process ( called photoelectrocatalytic process) is a promising technique to decrease electron-hole recombination and save energy (Shang et al, 2007; Ku et al, 2010a; Liu et al, 2011). By applying bias potential to the photocatalyst, an external electrical field is occurred to drive the photogenerated electrons and holes in opposing directions and decreases the electron-hole recombination (Ku et al, 2006). To enhance the photocatalytic decomposition, the energy consumption of applying bias potential was reported to be much more efficient comparing with applying higher light intensity (Ku et al, 2010a)

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