Fig. 2

Physical characterization of m-CoSe₂. a STEM image of a typical m-CoSe₂ nanobelt. Scale bar, 100 nm. b STEM-EDX elemental mapping of m-CoSe₂, showing the homogeneous distribution of Co (red) and Se (yellow), respectively. Scale bar, 50 nm. c Atomic-resolution image reconstructed by overlapping the inverse FFT patterns shown in Supplementary Fig. 18c, d. Scale bar, 5 nm. d Atomic-resolution HAADF-STEM image of m-CoSe₂. The regions marked by the red and yellow dashed squares indicate c-CoSe₂ and o-CoSe₂, respectively. Inset in d gives corresponding FFT pattern, exhibiting two sets of patterns from the [111] zone axis of c-CoSe₂ and [100] zone axis of o-CoSe₂. e, f High-magnification HAADF-STEM images taken from the red and yellow dashed squares in d, respectively. Scale bars, 1 nm. Insets in e and f show the corresponding FFT patterns, evidencing the c-CoSe₂ and o-CoSe₂ phases, respectively. g–i XRD patterns (g), Raman spectra (h), and UPS spectra (i) of the c-, o-, and m-CoSe₂.