Polydopamine-graphene/Ag–Pd nanocomposite as sustainable catalyst for reduction of nitrophenol compounds and dyes in environment

In this work, for the first time a new nanocomposite Ag–Pd-PDA/rGO was prepared in order to lower the consumption of palladium and to increase the catalytic activity of Pd with synergic effect. The prepared nanocomposite (Ag–Pd-PDA/rGO) was characterized using several analytical techniques such as FT-IR, XRD, TEM, SEM, EDX map, and BET. The effect of PDA and molar ratio of bimetal were investigated in morphology, size and catalytic activity of nanocomposite. The SEM and TEM showed that surface of PDA/rGO was decorated with Ag–Pd nanoparticles with cluster form in average diameter of 60 nm. The prepared nanocomposite was used as a new catalyst for reduction of nitro aromatic compounds such as 4-nitrophenol (4-NP) to 4-aminophenil (4-AP) and reduction of anionic and cationic dyes at 25 °C. Fortunately, the obtained results showed that the catalytic activity of Ag–Pd-PDA/rGO has been increased about 10 times in comparison to the Ag–Pd/rGO. The apparent kinetics of reduction has pseudo-first-order kinetics and the rate constant and TOF value was found to be 5.4×10−3 and 84741 h−1, respectively. The obtained catalyst showed high stability, leading to substrate conversion 98% after 5 cycles which supports the promising reduction of 4-NP.