Eco-friendly seeded Fe₃O₄-Ag nanocrystals: a new type of highly efficient and low cost catalyst for methylene blue reduction

Hybrid Fe₃O₄-Ag nanocrystals, a new type of highly efficient and reusable catalyst for methylene blue (MB) reduction, are fabricated by a novel seed deposition process. X-ray diffraction and Mössbauer spectroscopy results show that the developed iron oxides are in a pure magnetite Fe₃O₄ phase. Upon manipulating the amount of Ag seeds capsuled on the modified surfaces of Fe₃O₄ nanocrystals, the catalytic capacities on the reduction of MB can be precisely adjusted with a tunable fabrication cost control. The linear correlation of the reduced MB concentration versus reaction time catalyzed by our developed hybrid Fe₃O₄-Ag nanocrystals is coherent with pseudo first order kinetics. Importantly, with remarkable recyclability features, the hybrid Fe₃O₄-Ag nanocrystals can be easily separated by applying an external magnetic field. The tailored catalytic performances of the hybrid Fe₃O₄-Ag nanocrystals during MB reduction are attributed to the optimized dynamic electron transfer process, which dominates the electrochemical mechanism wherein the nucleophilic BH₄ ⁻ ions donate electrons to electrophilic organic MB through Ag seeds in a regulated amount. Such developed hybrid Fe₃O₄-Ag nanocrystals pave the way towards the mass production of highly efficient and low cost catalysts for methylene blue reduction.