fig1

Figure 1. (A) The XRD patterns of La-doped MnO₂ and MnO₂; (B) The crystal structure of α-MnO₂; The SEM images of (C) the sea urchin-like MnO₂ and (D) La-doped MnO₂ (The inset shows the particle size distributions); (E) The TEM and (F) HR-TEM images of La-doped MnO₂ (The inset shows the corresponding FFT pattern); (G) The HAADF-STEM image and the corresponding elemental mapping images of the La-doped MnO₂. XRD: X-ray diffraction; SEM: scanning electron microscopy; TEM: transmission electron microscopy; HR-TEM: high-resolution transmission electron microscopy; HAADF-STEM: high-angle annular dark field scanning transmission electron microscopy; FFT: fourier filter transformation.