Co and Co-P catalysts electroplated on Cu in sulfate based solution without or with an addition of H2PO2- ions were developed for hydrogen generation from alkaline NaBH4 solution. The microstructures of the Co and Co-P catalysts and their hydrogen generation properties were analyzed as a function of cathodic current density and plating time during the electrodeposition. An amorphous Co-P electrodeposit with micro-cracks was formed by electroplating in the sulfate based solution containing H2PO2- ions. It was found that the amorphous Co-P catalyst formed at 0.01 A/cm(2) exhibited 18 times higher catalytic activity for hydrolysis of NaBH4 than did the polycrystalline Co catalyst. The catalytic activity of the electrodeposited Co-P catalyst for hydrolysis of NaBH4 was found to be a function of both cathodic current density and plating time, that is, parameters determining the concentration of P in the Co-P catalyst. Especially, Co-13 at.% P catalyst electroplated on Cu in the Co-P bath at a cathodic current density of 0.01 A/cm(2) for 1080 s showed the best hydrogen generation rate of 954 ml/min g-catalyst in 1 wt.% NaOH + 10 wt.% NaBH4 solution at 30 degrees C. (c) 2006 Elsevier B.V. All fights reserved.