Green synthesis and enhanced photocatalytic performance of Co-Doped CuO nanoparticles for efficient degradation of synthetic dyes and water splitting
Daniel Masekela, Lovedonia K. Kganyakgo, Kwena D. Modibane, Tunde L. Yusuf, Sheriff A. Balogun, Wilson M. Seleka, Edwin Makhado
Abstract
• We developed Co-doped CuO NPs prepared via one pot green synthetic route. • Cobalt(Co)-doping can improve the separation of electrons and holes. • The Co-doped CuO NPs can degrade organic pollutants and produce hydrogen simultaneously. • The Co-doped CuO showed photostability over a period of cycle. • Photocatalytic mechanism was also further discussed in details. A highly effective Co-doped CuO photocatalyst was fabricated using a one-pot green synthetic route for photocatalytic decomposition of methylene blue (MB). The synthesized materials were confirmed using Field emission-scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), Thermogravimetric analysis (TGA) and Fourier transform infrared spectroscopy (FTIR). The optical and electrochemical properties, including the energy band gap, transient photocurrent response (TPR), and charge-transfer resistance (R ct ), were assessed using chronoamperometry (CA), and electrochemical impedance spectroscopy (EIS), respectively. The results from TPR, and EIS revealed that cobalt doping effectively promotes the separation of photogenerated charge carrier’s, diminishing recombination and thereby improving photocatalytic activity. The evaluation of photocatalytic activity revealed that the fabricated Co-doped CuO nanoparticles (NPs) demonstrated excellent photocatalytic activity compared to pure CuO NPs. Under UV–vis light irradiation, Co-doped CuO NPs achieved photocatalytic degradation efficiency of about 88 % within 100 min, whereas for pristine CuO NPs it was 75 % under the same irradiation time. The highest degradation efficiency achieved by Co-doped CuO NPs was ascribed to their improved electron and hole separation. Moreover, the scavenger experiment showed that the primary active species responsible for the photocatalytic decomposition of MB were hydroxyl radicals (•OH) and holes (h + ), followed by electrons (e - ) and superoxide radicals (•O 2 – ). The developed Co-doped CuO photocatalyst was highly stable even after 5th cycle. Additionally, the results demonstrated that the Co-doped CuO nanocomposite displayed a significantly higher water-splitting activity. This study offers a valuable reference for metal doping in photocatalyst semiconductors for effective photocatalytic removal of organic contaminants and hydrogen production.