Fig. 1. X-ray diffraction patterns of CuO arrays synthesized under different reaction time of water bath

Fig. 2. Scanning electron microscope (SEM) morphologies of CuO nanosheet arrays synthesized under different reaction time of water bath. (a) 5 min, low power; (b) 5 min, high power; (c) 10 min, low power; (d) 10 min, high power; (e) 15 min, low power; (f) 15 min, high power

Fig. 3. X-ray energy dispersion spectrum of CuO synthesized after 10-min reaction time of water bath

Fig. 4. XPS analysis of CuO synthesized after 10-min reaction time of water bath. (a) Cu 2p spectra; (b) O 1s spectra

Fig. 5. 100-cycle life tests for CuO nanosheet arrays synthesized under different reaction time of water bath at magnification of 0.4C