Efficient photocatalytic oxidation of VOCs using ZnO@Au nanoparticles

The emission of toxic VOCs (Volatile Organic Compounds) in the environment causes serious problems and, if from one side there are directives to reduce this threat, from the other side there are stringent necessities for their removal. Several methods have been proposed to remove toxic VOCs, but little attention has been paid towards their photooxidation using materials with improved photodetection. For these reasons, we account here on the good photocatalytic performance of semiconducting ZnO@Au nanostructures that revealed to be excellent for both ultraviolet and visible light detection, thanks to the wide ZnO band gap and visible Au surface plasmon resonance, towards the photooxidation of some toxic Volatile Organic Compounds. In particular, we tested these peculiar materials for the removal of some common VOCs as toluene, ethanol and formaldehyde under solar light irradiation. The ZnO@Au showed excellent performance in the total oxidation of toluene (95% of conversion) and formaldehyde (85%) with the consequent formation of only CO2 and water as by-products. This good activity was also confirmed in the photooxidation of ethanol that allowed to obtain the 72% of CO2 selectivity. Furthermore, in all tests the catalysts showed a good stability after several consecutive runs. The efficient electronic communication between the gold core and the zinc oxide shell permitted to enhance the overall photodetection of the solar irradiation, improving also the charge carriers separation. The ZnO@Au nanostructures can be considering promising candidates as photocatalysts for air purification.