Photoelectrochemical oxidation of benzyl alcohol in a continuous-flow microchannel reactor using titanium dioxide photoanode

Abstract

Fossil fuel, a primary energy source of humans, emits carbon dioxide and other greenhouse gases which have a high impact on the environment. Renewable energy development has been promised to solve the problem. Solar light, a renewable energy with an unlimited energy source, has gained attention to develop in various applications including energy production and catalytic chemical reactions. The photoelectrochemical process is a chemical catalysis technique that combines electrochemical and photocatalysis and has an advantage of low energy consumption due to solar energy support. In this work, the continuous-flow photoelectrochemical reactor was fabricated to undergo the oxidation reaction of benzyl alcohol into benzaldehyde. This work investigated the effects of electrolyte flow rate ranging from 0.05 to 0.20 ml/min on the percentage conversion of benzyl alcohol and the percentage selectivity of benzaldehyde. The most important part of a photoelectrochemical cell is photoelectrode for catalysis of the chemical reaction. Two different morphologies of TiO2, which are compact and mesoporous films were used as photoanodes for the photoelectrochemical reaction. The results showed that when the electrolyte flow rate was increased, the conversion was decreased, while the selectivity was increased. At the optimal conditions, the benzaldehyde selectivity of 43.11% was obtained when using the compact TiO2 film with the electrolyte flow rate of 0.1 ml/min (where the conversion is 55.98%). While for the mesoporous TiO2 film, 50.59% selectivity of benzaldehyde and 42.20% conversion was obtained at the electrolyte flow rate of 0.15 ml/min.