Electron-Beam Induced Water Removal, Phase Change, and Crystallization of Anodic-Electrodeposited Turbostratic Nickel Hydroxide-Oxyhydroxide

Abstract

Water removal, phase transformation, and crystallization of turbostratic nickel hydroxide and oxyhydroxide (Ni(OH)2‐NiOOH) are found to be inducible by the electron beam of a transmission electron microscope (TEM). Under 30 s of beam exposure at an accelerating voltage of 200 keV and a beam current density of 500 mA m−2, the original, characteristic turbostratic structure of Ni(OH)2‐NiOOH is observed to disappear, caused by the quick removal of intercalated water molecules by the electron beam. Increasing the current density from a low value of 1.5 mA m−2 to a high value of 500 mA m−2 can transform the Ni(OH)2‐NiOOH into nickel oxide (NiO) in 1 min. In situ heating and preheating experiments suggest that the transformation is caused by a heating effect induced by the electron beam. The results confirm that the mechanism previously discovered light‐induced actuation of Ni(OH)2‐NiOOH is caused by desorption of water molecules.