Chemical analyses were carried out in a Varian 715-ES ICP-Optical Emission spectrometer, after solid dissolution in H2SO4/H2O2 aqueous solution. Elemental analyses were performed by combustion analysis using a Eurovector EA 3000 CHNS analyzer and sulphanilamide as reference.
The morphology of the samples was studied by field emission scanning electron microscopy (FESEM) using a ZEISS Ultra-55 microscope.
The adsorption and desorption curve of N2 was measured at 77 K in an ASAP2420 Micromeritics device. The specific surface areas were calculated by the Brunauer–Emmet–Teller (BET) method following Rouquerol's criterion.
Thermogravimetric and thermal differential analysis (TG-DTG) were conducted in air stream with a NETZSCH STA 449F3 STA449F3A-1625-M analyzer (temperature ramp: 25 °C/10.0 (°C/min))/800 °C).
Infrared (FTIR) spectra were recorded in a PIS 100 spectrometer. The solid samples, mixed with KBr, were pressed into a pellet.