Fig. 2: Structural characterization of N–CuO.

a Schematic presentation of CuO structure (Top: CuO, Bottom: Nitrogen substitution site.). b HAADF-TEM image of N–CuO. Inset is the corresponding FFT pattern. The corresponding atomic model (c) and the corresponding elemental mapping images (d) of N–CuO. e Cu L-edge EELS spectra of CuO and N–CuO. Refined XRD profile (f) and Raman spectra (g) of the CuO and N–CuO. h TOF-SIMS of N–CuO.