The effect of morphology-dependent surface charges of iron oxide on the visible light photocatalytic degradation of methylene blue dye

The iron oxide powder was prepared using the surfactant Pluronic P123 with either iron nitrate (N series) or iron chloride (C series) as the raw material for iron source, under different pH conditions. The crystal phase, particle size, surface charge, and morphology of the iron oxide materials prepared by hydrothermal route were found to be highly influenced by the raw materials, and pH conditions of the preparation medium. Irrespective of iron source used, the formation of nanorods was favorable in the case of the basic medium. The iron oxide nanorods (NPBC) with high negative surface charges (− 20.8 mV) outperformed the other iron oxide samples having different morphologies like hexagonal (− 13.8 mV), oval (− 13.4 mV), and agglomerated nanoparticles (+ 12 mV) in the methylene blue degradation with ~ 86% of degradation observed for a very low catalyst loading of 10 mg. A methylene blue degradation of 69, 59, and 39% were observed for hexagonal, oval, and agglomerated nanoparticles, respectively, for the similar amount of catalytic loading. The sample NPBC exhibits a degradation rate constant value of 3.27 × 10 –4 s −1 which was 2.9 times higher than the agglomerated nanoparticles with a rate constant value of 1.14 × 10 –4 s −1 and the reasons are discussed.