Co-B flowers with mesoporous structure were first prepared via reduction of cobalt acetate by potassium borohydride in the presence of complexing agent ethylenediamine. The as-prepared Co-B flowers were characterized by Fourier transform infrared spectroscopy, X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, inductively coupled plasma atomic emission spectroscopy, X-ray photoelectron spectroscopy, N-2 adsorption-desorption, and magnetic performance test. The Co-B flowers exhibited enhanced coercivity, and weakened saturation magnetization and remanet magnetization as compared with the regular Co-B. During the hydrolysis of KBH4, the Co-B flowers exhibited higher catalytic activity than the regular Co-B. It is attributed to the larger specific surface area and mesoporous channels. During the successive reactions, the conversion of KBH4 over Co-B flowers was about 97%. The average H-2 generation rate of Co-B flowers was 4620 mL/min/g-catalyst in 1.5 wt% NaOH + 15 wt% KBH4 solution, which may give a successive H-2 supply for a 748 W polymer electrolyte membrane fuel cell (PEMFC) at 100% H-2 utilization. (C) 2007 Elsevier Ltd. All rights reserved.