Microstructure and catalytic activity towards the hydrogen evolution reaction of electrodeposited NiPx alloys

Electrodeposited NiPx alloys have been studied using electrochemical techni ques, transmission electron microscopy and electron diffraction. The result s show that crystals in the nanometer range are 'floating' in an amorphous phase. The crystal size is correlated with the catalytic activity of hydrog en evolution in an alkaline solution, it was found that the activity increa sed when the crystal size decreased. Electron diffraction patterns of the c rystals showed that when few crystals were observed, they were found to be pure Ni. NI,P was found only when considerable amount of crystals had been formed. With the formation of Ni,P the activity was reduced. It is proposed that the increased catalytic activity is caused by an increased amount of amorphous phase surrounding the Ni crystals. This phase is able to absorb l arge amounts of hydrogen, thereby changing the electronic structure of the electrode material. (C) 2001 Elsevier Science Ltd. All rights reserved.