3. Results and discussion
XRD pattern of the MgAl(CO3)-LDH sample (Figure 1A) shows clear diffraction peaks at 12.2°, 24.3°, 34.9°, 39.1°, 47.2°, 61.2° and 62.3°, which correspond to (003), (006), (009), (015), (018), (110) and (113) diffractions of a hydrotalcite phase.37 To delaminate LDH into monolayer, the interlayered CO32− were replaced by NO3 ions. Figure 1B displays the (003) characteristic peak shifts from 12.2° to 10.2° and the corresponding layer spacing expands from 0.77 nm to 0.89 nm, which confirms that the anions between the hydrotalcite layers have been exchanged from carbonate to nitrate. Figure 1C and 1D are the scanning electron microscopy (SEM) images of MgAl(CO3)-LDH and MgAl(NO3)-LDH. It is found that they have similar regular hexagonal shape, and their particle size distribution is around 1.7−2.5 μm.