Preparation of acid-resistant core/shell Fe ₃O ₄@C materials and their use as catalyst supports

Core/shell materials with a movable Fe ₃O ₄ core and a carbon shell were prepared using polypyrrole as carbon precursor. They are good candidates as metal catalyst supports due to their magnetic property and large surface area. The outer carbon shell thickness could be well-controlled. In addition, the Fe ₃O ₄@C materials displayed good resistance to acids, which would greatly extend their range of use. Because nitrogen atoms originating from pyrrole rings still remained in the carbon shell after calcination, Pd nanoparticles could be anchored on the surface without aggregation. The Fe ₃O ₄@C/Pd materials showed excellent catalytic performance in the reduction of methylene blue with sodium borohydride as reducing agent. The catalysts could be easily recycled by an external magnetic field and reused without obvious activity loss.