Bi2Fe4O9 powders with different morphology and particle size have been prepared via surfactant-free solvothermal route with water and water-ethanol mixed solvents. The as-synthesized samples were characterized by powder X-ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy and UV-vis spectroscopy. The effect of the solvent on the morphology of Bi2Fe4O9 crystals and the formation process of rod-like microrods and defective crystals were investigated. Rod-like and cubic shape Bi2Fe4O9 crystals could be easily obtained by changing the volume ratios of H2O/EtOH. The results indicate that the rod-like Bi2Fe4O9 crystals could be formed in the more ionic solvent, and the anisotropic nature of the crystal structure may be responsible for the formation of rod-shape. In addition, the optical properties and photocatalytic activity of the Bi2Fe4O9 samples were investigated. The lower photocatalytic activity of Bi2Fe4O9 microrods could be attributed to their larger particle size, smaller specific surface areas and smaller bandgap. (C) 2014 Elsevier B.V. All rights reserved.