A Comprehensive study on the reduction of 4-NP using Au/Polydopamine catalysts

Here, Au/polydopamine (Au/PDA) catalysts were prepared by gold sol adsorption (Au/PDA(Sol)), PDA in situ reduction (Au/PDA(PDA reduction)) and DA in situ reduction (Au/PDA(DA reduction)). The factors that influence the performance of Au-PDA on the reduction of 4-nitrophenol (4-NP), were systematically studied for the first time. The catalytic performance of Au/PDA(Sol) is the best because of the uniform and small size of Au nanoparticles (NPs) (3.2 ± 0.7 nm), with a turn over frequency (TOF) of 10125 h −1 , a mass-normalized rate constant ( k’ ) of 33360 min -1 g Au -1 and an apparent activation energy (Ea) of 11.39 KJ/mol. It is confirmed that there are electronic interactions between Au and the catechol hydroxyl groups and imino groups of PDA. Some unreduced Au 3+ ions can be reduced in situ by NaBH 4 during the catalytic reaction, forming ultra small Au NPs and leading to a good initial catalytic activity, especially for Au/PDA(DA reduction). This work systematically studied the influencing factors in catalysis for Au/PDA, providing guidance for the preparation and industrial application of PDA supported noble metal catalysts.