Figure 3

XRD patterns of Cu@CuS of the first reaction and Cu@CuS-0.5, Cu@CuS-2, Cu@CuS-8, Cu@CuS-12 that obtained from the secondary reaction for 0.5 h, 2 h, 8 h and 12 h, respectively.

XRD patterns of Cu@CuS of the first reaction and Cu@CuS-0.5, Cu@CuS-2, Cu@CuS-8, Cu@CuS-12 that obtained from the secondary reaction for 0.5 h, 2 h, 8 h and 12 h, respectively.