N-doped carbon dots/MnO₂ composite for the efficient catalytic reduction of malachite green and methyl violet

Here in, N-doped carbon dots/MnO₂ (NCDs/MnO₂) composite was synthesized via a facile one-pot method, utilizing the reducing properties of NCDs to convert KMnO₄ into MnO₂. Characterization techniques, including XPS, TEM, FTIR, and XRD, confirmed the successful formation of the composite. The catalytic performance of the NCDs/MnO₂ composite was evaluated for the reduction of malachite green (MG) and methyl violet (MV) dyes in the presence of NaBH₄. The composite exhibited excellent catalytic activity with over 96.0% MV reduction in 14 min and 96.5% MG was reduced in 12 min. Kinetic studies revealed pseudo-first-order reaction kinetics, with rate constants of 0.2087 ± 0.0113 min⁻¹ for MV and 0.1288 ± 0.0083 min⁻¹ for MG. Moreover, the composite demonstrated excellent reusability, maintaining high catalytic efficiency over multiple cycles. These findings highlight the potential of the NCDs/MnO₂ composite as a promising and sustainable catalyst for the treatment of dye-contaminated wastewater, contributing to environmental remediation efforts.