The hydrogen evolution reaction (HER) was studied on Ni-P electrodes prepared by electrodeposition at temperatures varying from 23 degrees C to 65 degrees C. The activities for the HER of the electrodes first decreased slowly with the increasing temperature of the Ni-P preparation. A sudden decrease in the HER activity occurred on the electrode prepared at 65 degrees C. Similar dependence was found for the variation of the amounts of absorbed hydrogen with the electrodeposition temperature of the Ni-P electrodes. The behavior of Ni-P electrodes prepared from Ni-P powders was quite different. (Ni-P powder was prepared by peeling off the Ni-P layer and by milling the leaves of the Ni-P alloy in a vibrating ball mill.) The Ni-P powder electrodes displayed little activity independently of the temperature of the Ni-P powder preparation. It was followed from the results that the high activity for the HER of the layer Ni-P electrodes prepared at T < 53 degrees C was caused by the internal stress in the layer. The stress originated during the electrodeposition of the Ni-P layer by co-deposited and absorbed hydrogen. (c) 2008 Elsevier Ltd. All rights reserved.