Interaction of hydrogen with ZnO nanopowders--evidence of hydroxyl group formation.

There have been many investigations to reveal the nature of the hydrogen gas and ZnO nanopowder interaction at elevated temperatures, while at present no conclusive description of such an interaction has been confidently reported. In this work, we demonstrate that a hydroxyl group is formed during this interaction, depending on size and relative crystallinity of nanopowders. Our in situ Raman spectroscopy investigations show that the interaction directly affects the intensity of the Raman signal at 483 cm(-1), relative to the peak at 519 cm(-1). Ex situ x-ray diffraction (XRD) and infrared spectroscopy also show extra peaks at 44° and 1618 cm(-1), respectively, after hydrogenation. These peaks were all identified as surface hydroxyl groups, which can be related to the formation of water on the ZnO nanopowder surfaces.