Degradation of methylene blue under visible-light with copper-doped cobalt oxide nanoparticles

Background: The development of efficient photocatalysts is greatly essential to degrade organic pollutants such as methylene blue (MB). Copper-doped cobalt oxide nanoparticles (Cu-Co3O4 NPs) have shown promise in enhancing photocatalytic activities due to their unique structural and optical properties. Method: A hydrothermal approach was employed to synthesize Cu-Co3O4 NPs with varying Cu concentrations for the degradation of MB. XRD confirmed the cubic structure of Co3O4 NPs, with crystallite sizes decreasing from 29 nm (pure Co3O4) to 20 nm (15 % Cu-doped Co3O4). The FE-SEM/TEM micrographs revealed distinct shapes and morphologies. Additional peaks of the used Cu-Co3O4 NPs indicated interactions with MB. XANES and EXAFS analyses indicated electron transitions and structural modifications due to increased lattice strain with higher Cu concentrations. Significance finding: This study reveals that Cu-Co3O4 NPs exhibited great performance compared to pure Co3O4 NPs. The Cu doping in Co3O4 nanoparticles enhanced their photocatalytic activity, achieving the highest degradation efficiency of 89 % for MB in 90 min under visible light with 15 % Cu doping. The results indicate the potential of Cu-Co3O4 NPs for the degradation of MB, offering valuable insights into the underlying mechanisms and practical applications of these catalysts. The optical band gap decreased from 3.1 eV for undoped Co3O4 to 2.1 eV for 15 % Cu-doped Co3O4 but increased after degradation, demonstrating their potential applications for environmental cleanup.