Unexpected Photocatalytic Activity of Simple and Platinum Modified Tubular SiO2 for the Oxidation of Oxalic Acid to CO2

Abstract

The photocatalytic mineralization of oxalic acid over SiO2-based materials was investigated in the 200–800 nm range. The photocatalytic activity was found to be strongly related to the morphology of SiO2 materials. The simple as well as the Pt-modified SiO2 particles having a predominant spherical shape exhibited null photocatalytic activity. In contrast, the tubular shaped SiO2 particles revealed an interesting photocatalytic activity, the rate of CO2 evolvement being 45 µmol gcat−1 h−1. The initial activity was significantly enhanced (428 µmol CO2 gcat−1 h−1) by platinum photodeposition on the outer and inner surface of tubular SiO2. The catalytic materials were characterized by TEM, UV–VIS and XPS to obtain rational explanations for the phocatalytic activity that was noticed. The experiments revealed that SiO2 tubes behave as efficient photooxidation microreactors. The morphology-dependent photocatalysis can be an efficient tool in future for the abatement of pollutants in liquid phase.