Investigating the impact of chemical structures on the photocatalytic degradation rates over ZnO nanorods: An oxidative pathways perspective.

Zinc oxide (ZnO) nanorods were coated on glass substrates and used as photocatalysts to evaluate the kinetic behavior of three different aromatic structures: i) single aromatic ring (phenol), ii) poly-aromatic ring (methylene blue), and iii) complex macromolecule (humic acid). The kinetics of all the tested molecules obey a pseudo-first-order model regardless of their initial concentrations. The apparent rate constants are largely controlled by the bond dissociation energy and the number of oxidation steps in each organic molecule. For instance, methylene blue presents the weakest dissociation bond energy and the highest degradation rate constant compared to humic acid and phenol. [Display omitted] • ZnO nanorods were deposited on glass substrates by hydrothermal growth method. • Photocatalytic tests were carried-out on methylene blue, humic acid & phenol. • Degradation mechanisms over ZnO photocatalysts follow pseudo-first-order kinetics. • Oxidative pathways are directly governed by the chemical structure of each molecule. • Apparent rate constants are depend on bond dissociation energies & oxidative steps. [ABSTRACT FROM AUTHOR]