Fig. 1. Morphology of rGO@MnO₂ nanoparticles. (a) Raman spectrum of GO, rGO, and rGO@MnO₂. (b) XPS high-resolution scans of Mn 2p in rGO@MnO₂ nanoparticles. (c) TEM images of rGO@MnO₂. (d) TEM images of rGO@MnO₂ nanoparticles with a high-magnification image of crystals. (e) Elemental mapping of C, O and Mn of rGO@MnO₂ nanoparticles.