Facile synthesis of Pd nanoparticles on polydopamine-coated Fe-Fe2O3 magnetic nanochains as recyclable high-performance nanocatalysts

Abstract In this work, we report on the green synthesis of a self-mixing nanocatalyst based on Pd nanoparticles on polydopamine-coated Fe-Fe2O3 magnetic nanochains (Fe-Fe2O3@PDA@Pd), which were obtained using core@shell structured Fe-Fe2O3@PDA magnetic nanochain as carrier and palladium chloride as metal precursor through in situ galvanic replacement reaction between catechol groups of PDA and palladium ions in aqueous solution at room temperature. In this process, palladium ions were directly reduced to ultrafine metallic Pd (0) by catechol groups of PDA, which was oxidized to quinone groups. No any external reductant or surfactant were added. Characterization results shows the Fe-Fe2O3@PDA@Pd nanocatalysts can self-rotate as nano-sized stirring bar to boost the reaction rate under magnetic stirrer due to its high saturation magnetization (Ms = 105 emu g−1). For the 4-nitrophenol (4-NP) reduction and methylene blue hydrogenation in presence of NaBH4, the rate constants of Fe-Fe2O3@PDA@Pd were up to 0.55 min−1 and 0.90 min−1 respectively, which are far higher than those of the contrast sample Fe-Fe2O3@Pd. Moreover, the nanocatalysts can be reused at least 6 runs with excellent yields for both the reactions. These facilitate the practical application of the Fe-Fe2O3@PDA@Pd nanocatalyst in reduction of nitroaromatic compounds and other hydrogenation processes.