In addition, the (001) peak is eliminated in the XRD pattern of VG-S, which represents the highest reduction degree was achieved in this study. The free-standing membranes were also characterized by XRD (Figure ) to further understand the in-situ reduction process. In Figure , compared to Figure , a similar variation trend of (001) peak can be found. However, anomalously, in VGMs, with the decrease of (001) peak signal, the signal of (002) peak is not increased and even not obviously appeared (Figure ), and only sample VGM 200 exhibits a broad (002) peak centered at around 21° (Figure ). This gives a hint that the in-situ reduction may cause the disorder of the laminar alignment in the membrane due to the incomplete removal of functionalities on the GO basal plane.