Structure Evolution and Hydrogenation Performance of IrFe Bimetallic Nanomaterials

By a reverse microemulsion method, a series of IrFe bimetallic nanomaterials of variable morphologies and compositions is synthesized and characterized by (57)Fe Mössbauer spectroscopy, XRD, XPS, and TEM. The structure evolution, such as IrFe alloy nanoparticles to Ir nanoparticles on Fe2O3 flakes, can be simply tuned by changing the molar ratio of Ir to Fe precursors. In terms of Fe, the relative content of IrFe alloy decreased with the increase of Fe species doped, while that of Fe2O3 flakes increased until reached 100%. The as-prepared IrFe bimetallic nanomaterials were served as catalysts for the selective hydrogenation of 3-nitrostyrene to 3-aminostyrene, and it is found that the catalytic performance was related to the morphology and composition of these nanomaterials. Ir1Fe4 was subsequently identified to be a highly active and exceedingly selective catalyst with good stability and recyclability for the hydrogenation of 3-nitrostyrene, underscoring a remarkable "synergistic effect" of the two metals appearing as the form of Ir nanoparticles loaded on Fe2O3 flakes. For Ir nanoparticles, they act as an active species for the hydrogenation; for Fe2O3 flakes, they favor the preferential adsorption of nitro groups, which account for the better chemoselectivity to objective product.