The morphologies of the samples were further characterized
using SEM measurement. As shown in Fig. 4, Al-Air HT has a threedimensional
aggregated structure with irregular morphology,
while Al-GO-Air HT has a two-dimensional nanosheet structure
similar to those of GO-N2 HT and Al-GO-N2 HT. This indicates that
when GO was used as a template, the nucleation and growth of
aluminum oxide mainly occurred on the surface of GO due to the
interaction between the aluminum precursors and the functional
groups on the surface of GO. By contrast, for Al-Air HT there was no
hetero-surface for alumina precursor to interact, and therefore it
led to a homogeneous nucleation and growth of aluminum oxide in
bulk solution, forming a bulk structure consisting of irregular sized
particles.