Aluminum-doped alpha-Ni(OH)(2) microspheres with flowerlike hierarchical structure (H-Al-alpha-Ni(OH)(2)) were successfully synthesized via a facile hydrothermal method with the assistance of ionic liquid (1-butyl-3-methyl imidazolium tetrafluoroborate, [BMIM]BF4). The XRD pattern and elemental analysis confirm that aluminum species incorporates into the lattice of alpha-Ni(OH)(2): SEM and TEM images reveal that the as-prepared microspheres are composed of numerous frizzy nanoflakes shell attaching vertically to the core. The resulting H-Al-alpha-Ni(OH)(2) sample exhibits a specific surface area of 91.2 m(2)/g and a mesopore distribution (2-20 nm) based on the BET measurements. Furthermore, the hierarchical H-Al-alpha-Ni(OH)(2) modified electrode displays a couple of well-defined reversible redox peaks (Delta E-p = 67 mV and I-a/I-c = 0.91) and a fast direct electron transfer rate constant (k(s) = 3.32 s(-1)), owing to the high dispersion of active species as well as abundant mass transfer channels which facilitate the mass/electron transfer. In addition, the modified electrode presents a significant electrocatalytic performance towards the oxidation of hydrazine with a linear response range (5.0 x 10(-6)-1.0 x 10(-4) M), high sensitivity (144 mu A/mu M cm(2)), low detection limit (0.8 mu M) as well as good stability. The hierarchical alpha-Ni(OH)(2) with largely enhanced electrochemical behavior demonstrated in this work can be used in electrochemical sensor and electroanalysis. (C) 2012 Elsevier Ltd. All rights reserved.