New Features and Uncovered Benefits of Polycrystalline Magnetite as Reusable Catalyst in Reductive Chemical Conversion

Abstract

Magnetite is one of the most well-characterized and used iron oxides in a variety of research and industrial fields. Its easy separation by magnetism has attracted great attention for use as a support material for various noble metallic catalysts. Here, we report for the first time that bare polycrystalline magnetite can show a remarkable catalytic activity toward p-nitrophenol reduction by sodium borohydride, while three other single-crystal magnetite samples exhibit little effect on the catalysis. Electron and atomic force microscopies and Mossbauer spectrometry showed that elemental Fe nanoparticles were formed on the surface of polycrystalline magnetite. Density functional theory calculation further elucidated that the Fe atom exposed at the high-index magnetite surface develops a significant FeBH3 interaction and that its leaching-out process can be substantially promoted. Surprisingly, recycling tests showed that this great activity could be fully preserved up to 10 reaction cycles, in contrast to the other noble metal-based catalysts that showed a decrease in the catalytic activity as the reaction cycle increased.