Fig. 2

a–c SEM and TEM images showing that the Co₃O₄ particles were 50–200 nm sized and the interplanar distance of 0.233 nm corresponded to the stacking of (311) planes. d–f SGP reduced the particle size down to sub-20 nm, while the similar (311) stacking was observed with an interplanar distance of 0.244 nm. g, h XRD patterns and N₂ adsorption-desorption isotherms for the Co₃O₄ and Co₃O₄/SGP powders