Mn²⁺ Doped Cobalt Oxide and Its Composite with Carbon Nanotubes for Adsorption-Assisted Photocatalytic Applications

In this study, cobalt oxide (Co₃O₄), Mn-doped Co₃O₄ (MDCO), and Mn-doped Co₃O₄-functionalized carbon nanotube (MDCO-CNTs) were synthesized via the co-precipitation method using cobalt nitrate and manganese nitrate as a cobalt and manganese precursor, respectively. Synthesized materials were assessed using different characterization techniques like scanning electron microscopy, X-ray diffraction, and UV-visible spectroscopy. Congo red in an aqueous solution was adopted as the model dye to estimate the adsorption-assisted photocatalytic efficiency of the synthesized materials. The samples studied for adsorpsstion-assisted photocatalysis were found to be highly effective and among all the samples, the best removal performance (80%) was obtained by treating the MDCO-CNTs composite for 50 min at 50 °C. Mathematical modeling shows that all of the samples followed a pseudo-second-order kinetic model and data best fitted to a Langmuir isotherm, implying that the process involved in the removal of Congo red dye is chemisorption.