The photocatalytic activity (Fig. ) of morphologically different iron oxides (FeAH, FeBH, FeCT, FeMC, FePM) nanoparticles was investigated to understand the role of structural (size, shape, and surface) differences. The setup facilitated the interaction of broad-spectrum tropical sunlight with the rhodamine dye in an aqueous solution. Thus, the overall experiment involves the nanoscale metal oxide-based dye degradation. Noticeably, metal oxide-based photocatalysis and its mechanisms have been studied extensively during the past few decades. However, there has been greater emphasis on selected materials like TiO2, RuO2, and ZnO. On the part of mechanisms, aspects like light absorption, charge carrier dynamics, surface states, and quantum efficiency have received much attention. However, we, in this study, have attempted to understand the interfacial charge transfer at the iron oxide-dye interface using an electrochemical approach. Considering this, the dye concentration was kept low, i.e., 0.596 x 10 -3 M with a moderate catalyst load of (0.1 g/L). This low concentration of dye was intended to decrease the possibility of multilayer adsorption of the dye on the catalyst surface after the adsorption-desorption equilibrium. This, in summary, will allow the weakening of the non-linearities in the photocatalytic activity of the catalyst due to the concentration effect. Also, the set-up with this configuration may shed light on the real cases in nature where mineral oxide, humic substances, and pollutants interact under sunlight. The progress of photocatalytic degradation was monitored (Fig. ,a-f) using the absorption coefficient (ε) corresponding to λmax of 540 nm.