In this study, nitrogen-doped graphene quantum dots (NGQD) decorated CuWO₄ nanocomposite (NGQD-CuWO₄) were synthesized for enhanced photocatalytic tetracycline (TC) degradation under visible light irradiation. The incorporation of NGQDs significantly increased light absorption, narrowed the band gap, and improved charge transfer in CuWO₄, leading to enhanced photocatalytic efficiency. TEM analysis confirmed the successful integration of NGQDs with CuWO₄, showing uniform dispersion and lattice fringes, while Raman spectra revealed the characteristic D and G bands of NGQDs, indicating their graphene-like properties. The optimal NGQD loading (3NGQD-CuWO₄) achieved a degradation efficiency of 99 % within 90 min, exhibiting a three-fold increase in performance compared to pure CuWO₄. Photocurrent measurements indicated that incorporating NGQD enhanced the charge separation in CuWO₄ displaying the highest photocurrent density. The lowest charge transfer resistance observed in the hybrid photocatalyst is confirmed by electrochemical impedance spectroscopy (EIS), indicating the significant role of NGQD in increasing the charge transfer kinetics. Optical studies further demonstrated a significant red shift in the absorption spectrum and a reduction in the band gap from 2.43 eV for pure CuWO₄ to 2.29 eV for the 3NGQD-CuWO₄ composite. Kinetic studies indicated a pseudo-first-order reaction with a rate constant three times higher for NGQD-CuWO₄ compared to CuWO₄ alone. Hydroxyl radicals (^•OH) were identified as the main reactive species responsible for degradation. This work highlights that NGQD incorporation makes CuWO₄ an efficient, stable, and promising photocatalyst for environmental applications, particularly in treating pharmaceutical-contaminated water.

中文翻译：

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揭示氮掺杂石墨烯量子点对提高 CuWO4 纳米复合材料光催化性能的影响


在本研究中，合成了氮掺杂石墨烯量子点 （NGQD） 修饰的 CuWO₄ 纳米复合材料 （NGQD-CuWO₄），用于在可见光照射下增强光催化四环素 （TC） 降解。NGQD 的掺入显着增加了 CuWO₄ 中的光吸收，缩小了带隙，并改善了电荷转移，从而提高了光催化效率。TEM 分析证实了 NGQD 与 CuWO₄ 的成功整合，显示出均匀的色散和晶格条纹，而拉曼光谱揭示了 NGQD 的特征 D 和 G 带，表明它们具有类似石墨烯的特性。最佳 NGQD 负载 （3NGQD-CuWO₄） 在 90 分钟内实现了 99% 的降解效率，与纯 CuWO₄ 相比，性能提高了三倍。光电流测量表明，加入 NGQD 增强了 CuWO₄ 中的电荷分离，显示出最高的光电流密度。电化学阻抗谱 （EIS） 证实了在混合光催化剂中观察到的最低电荷转移电阻，表明 NGQD 在增加电荷转移动力学方面发挥着重要作用。光学研究进一步表明，吸收光谱有明显的红移，带隙从纯 CuWO₄ 的 2.43 eV 降低到 3NGQD-CuWO₄ 复合材料的 2.29 eV。动力学研究表明，与单独的 CuWO₄ 相比，NGQD-CuWO₄ 的速率常数高出三倍的伪一级反应。羟基自由基 （•OH） 被确定为负责降解的主要反应性物质。 这项工作强调，NGQD 掺入使 CuWO₄ 成为一种高效、稳定且有前途的光催化剂，可用于环境应用，特别是在处理受药物污染的水方面。