Carbon-supported Co(OH)(2) and Ni(OH)(2) catalysts are prepared to examine the mechanism of oxygen reduction reaction (ORR) on hydroxide catalysts. ORR via the 4-electron transfer pathway on a hydroxide undergoes oxidation of hydroxide by O-2 to form oxyhydroxide, followed by electrochemical reaction of oxyhydroxide to regain hydroxide. beta-Ni(OH)(2) has the same crystal structure and lattice parameters as beta-Co(OH)(2), but it exhibits a poorer catalytic activity toward ORR than beta-Co(OH)(2) at a low temperature. The poor catalytic activity of Ni(OH)(2)/C can be attributed to the difficulty in Ni(OH)(2) oxidation and the slow kinetics of NiOOH electroreduction to Ni(OH)(2). The catalytic activity of the Ni(OH)(2)/C catalyst is significantly improved through elevating the operation temperature because Ni(OH)(2) oxidation to NiOOH and NiOOH electroreduction are improved at a high temperature. A model of ORR via the 4-electron transfer pathway on transition metal hydroxides is suggested and discussed. (C) 2011 Elsevier B.V. All rights reserved.