Shape manipulation of porous CeO2 nanofibers: facile fabrication, growth mechanism and catalytic elimination of soot particulates

In this work, shape manipulation in porous CeO2 nanofibers was successfully achieved by a simple electrospinning technology with high quality and high reproducibility. By simply tuning the electric field strength during electrospinning, the diameter of as-spun nanofibers composed of Ce(acac)3 and polyvinylpyrrolidone can be precisely controlled. As a result, the morphology of nanofibers can change from columnar to celery-like and belt-like structure. The formation mechanism of this intriguing diameter-dependent morphology can be assigned to the gradient evaporation of solvent across the nanofiber. After calcination at 500 °C, porous CeO2 nanofibers were obtained, showing unusually observed celery-like or belt-like morphologies. These intriguing CeO2 nanofibers exhibited good thermal stability in terms of phase structures and morphologies up to 700 °C. The fibrous CeO2 mats were active toward soot combustion with decreased activation energy, compared with commercial samples. Among three kinds of shapes, the fibrous CeO2 mats made of columnar-like nanofibers were endowed with the lowest activation energy of 120.1 kJ/mol, due to the most effective contact between soot and CeO2 surface, regardless a loose contact mode.