Magneto-Revealing and Acceleration of Hidden Kirkendall Effect in Galvanic Replacement Reaction.

Rate and product control are crucial for a chemical process and are useful in a wide range of applications. Traditionally, thermodynamic parameters, such as temperature or pressure, have been used to control the chemical reactions. Here, by using the fabrication of a hollow MnxFeyO4 nanostructure as a model system, we report an experimental tuning of both chemical reaction rate and product by a high magnetic field. A 12 times magneto-acceleration of the galvanic replacement (GR) reaction was observed. Moreover, it is first demonstrated that a magnetic field can unravel and accelerate the hidden Kirkendall effect (KE) in addition to the pristine GR reaction. With coaction of magneto-tuned KE and GR, not only the rate but also the composition as well as magnetic property of the products could be modulated. These observations suggest that not only is a magnetic field a variable parameter that cannot be ignored, but also it can effectively control both rate and product in a chemical reaction, which provides a new route for chemical process controlling and shape/composition designing in material synthesis.