Green synthesis of bimetallic Pd-Ag alloy nanoparticles supported on polydopamine-functionalized kaolin for catalytic reduction of 4-nitrophe-nol and organic dyes

A green and universal synthesis strategy was demonstrated for preparation of bimetallic Pd-Ag alloy nanoparticles supported on polydopamine-functionalized kaolin (kaolin-PDA-PdAg), where bimetallic PdAg alloy was synthesized by co-reduction of Na2PdCl4 and AgNO3 with sodium citrate. Characterization results, including TEM results and XPS results, confirmed that bimetallic Pd-Ag was alloying state and kaolin-PDA-PdAg was successfully synthesized through mussel-inspired chemistry. The kaolin-PDA-PdAg nanocomposite exhibited excellent catalytic activity and performance towards reduction of 4-nitrophenol, whose rate constant was found to be 3.46 min-1 under condition of high concentration (10 mM) of 4-nitrophenol. Besides, kaolin-PDA-PdAg nanocomposite showed high catalytic performance for methyl orange and safranine-T as well. The high catalytic activity of kaolin-PDA-PdAg could be elucidated by electronic effect and synergistic effect of bimetallic Pd-Ag alloy. These results suggest that kaolin-PDA-PdAg composites could be applied as high-efficiency catalysts for reduction of 4-nitrophenol and degradation of organic dyes. Furthermore, abundance and low-priced of raw materials kaolin, green and versatility of synthetic method endow kaolin-PDA-PdAg composites with broad application prospects. Strategy of bimetallic Pd-Ag alloy anchored on kaolin in this text could provide an efficient platform for synthesis of bimetallic alloy nanoparticles loaded on various materials.