Tannic Acid-Decorated Bimetallic Copper–Gold Nanoparticles with High Catalytic Activity for the Degradation of 4-Nitrophenol and Rhodamine B

In this study, tannic acid (TA) was applied as a stabilizing agent for synthesizing bimetallic copper–gold (CuAu) nanoparticles. Cu(NO3)2 and NaAuCl4 were used as the sources of copper and gold ions, respectively, and NaBH4 was employed as a reducing agent. The prepared TA-CuAu nanoparticles were extensively characterized via ultraviolet–visible spectroscopy, Fourier transform infrared spectroscopy, transmission electron microscopy, X-ray diffraction, and zeta potential analyses. To evaluate their catalytic activity, the TA-CuAu nanoparticles and NaBH4 were applied in the degradation of 4-nitrophenol (4-NP) and rhodamine B (RB) individually and in a mixture. The individual degradation of 4-NP and RB was completed within 10 min, and the apparent rate constants were calculated as 0.3046 and 0.2628 min–1, respectively, emphasizing the efficient catalytic activity of the TA-CuAu nanoparticles. Additionally, controlled experiments were performed for the degradation of 4-NP and RB in the absence of catalysts or NaBH4 to investigate the kinetic feasibility of the catalytic reactions. A mixture of 4-NP and RB was successfully degraded within 10 min using the TA-CuAu nanoparticles as catalysts. Furthermore, the reuse of the catalysts after five successive cycles demonstrates an outstanding performance with no significant loss in the catalytic activity. Finally, the successful treatment of the tap and lake water samples spiked with 4-NP and RB using the TA-CuAu nanoparticles further confirmed their application potential as catalysts in environmental water remediation.