TEM and EELS characterization of Ni–Fe layered double hydroxide decompositions caused by electron beam irradiation

Abstract

Electron irradiation of Ni–Fe layered double hydroxides (LDHs) was investigated in the transmission electron microscope (TEM). The initial structure possessed a flat hexagonal morphology made up of crystalline domains with a well-defined hexagonal crystal structure. The Ni–Fe LDHs were susceptible to significant structural decompositions during electron irradiation. The generation of pores and crystallographic breakdown of the LDH routinely occurred. In addition, a compositional change was established by electron energy loss spectroscopy (EELS). During 300 kV irradiation, a pre-peak evolution in the oxygen K edge highlighted a transition to metal oxide species. In parallel, nitrogen K edge attenuation demonstrated interlayer mass-losses. It was found that TEM conditions profoundly affected the decomposition behaviours. At lower acceleration voltages, an increased dehydration rate of the LDH cationic layers is observed during irradiaton. Moreover, in situ specimen cooling revealed the retention of interlayer nitrates. An emphasis on the dehydroxylation processes and anionic mass-loss facilitation is discussed.