In-situ deposition of gold nanoparticles onto polydopamine-decorated g-C 3 N 4 for highly efficient reduction of nitroaromatics in environmental water purification.

A green synthesized gold-catalyst (PDA-g-C3 N4 /Au) for highly efficient reduction of nitroaromatics by NaBH4 was proposed. Polydopamine (PDA) served as the reductant and stabilizer for AuNPs reduction, avoiding the use of chemical reductant and stabilizer that may result in secondary contamination. g-C3 N4 not only acted as the support but also provided compatibility for AuNPs deposition, enhancing the stability and deposition of AuNPs, which improved the catalytic activity. Different experimental parameters including the amount of Au loading, concentration of NaBH4 , and dosage of catalyst were studied. Results showed that PDA-g-C3 N4 /Au(3) revealed higher catalytic activity with a rate constant of 0.0514 s-1 and TOF of 545.60 h-1 for 4-NP reduction. In addition, the catalyst was highly efficient in reduction of other nitroaromatics and the reduction rates of these compounds were found as the sequence: methyl orange > 2-nitrophenol > 2, 4-dinitrophenol > Erichrome Black T > Congo red. Moreover, the PDA-g-C3 N4 /Au(3) catalyst kept high stability and excellent conversion efficiency over ten reduction cycles. The practical application on different real water samples suggests that this Au catalyst has promising application in environmental water purification. The simple and green synthetic Au catalyst expands the range of application and provides potential application on environmental remediation.