The specific surface area of the powders was measured by the Brunauer–Emmett–Teller (BET)
method and the pore size distribution of the powders by the adsorption-desorption isotherm utilizing nitrogen as the adsorbate after drying at 80 °C for 12 h (Gemini 2375, Micromeritics Instrument Inc.,Norcross, GA, USA)