Structural and photocatalytic properties of Pd deposited semiconductors with different morphology

In this work, we studied the effect of Pd deposition (0.3 wt%) on the structural and photocatalytic properties of TiO2 anatase with different morphologies (nanoparticles, nanotubes and nanofibers). The Pd-deposited semiconductor samples were synthesized by a simple deposition-precipitation method and used as catalysts for photocatalytic degradation of p-nitrophenol under visible light illumination. Pd-deposited TiO2 nanofibers showed higher photocatalytic activity than Pd-deposited TiO2 nanoparticles or nanotubes. Pd-deposited (0.3 wt%) CeO2 and WO3 nanofibers were also synthesized to investigate whether the advantages of nanofiber morphology extend to other semiconductors, with lower and higher band gap energies. The performance of Pd-deposited CeO2 nanofibers was superior to that of all other Pd-deposited samples. The samples were characterized by elemental analysis, XRD, SEM, TEM, DR UV-vis, N-2 physisorption and XPS to investigate the role of structural properties on photocatalytic performance. The XRD data indicated that the crystal structures of TiO2, WO3 and CeO2 were not modified after Pd deposition and TEM indicated that the Pd was well dispersed on the semiconductor surfaces, with particle sizes <20 nm. Pd deposition changed the morphology of the CeO2 nanofibers to a unique 'mat-like' structure, with small (4 nm) Pd nanoparticles. This latter sample had the highest photocatalytic activity, which was attributed largely to high photocurrent density. Conditions for photocatalysis were investigated and Pd-deposited CeO2 nanofibres were shown to be reusable for at least five cycles, without significant loss of photocatalytic activity. Our study suggests that Pd-deposited CeO2 nanofibres could be used industrially to degrade p-nitrophenol.