UC Berkeley

In this study, we report a heterogeneously stacked MoS2-Graphene Oxide (GO) membrane that demonstrates enhanced resistance to restacking and swelling compared to homogeneously stacked pure MoS2 or GO membranes. The heterogeneous membrane was prepared using a mixture of MoS2 and GO suspensions with varying ratios. X-ray diffraction analysis reveals three stacking structures within the heterogeneous membrane: neighboring GO-GO, MoS2–MoS2, and MoS2-GO nanosheets. Combining XRD results and theoretical calculations, we determine that the alternately stacked MoS2-GO structure has an interlayer spacing of 0.86 ± 0.07 nm, with a free spacing of around 0.53 nm when dried. By optimizing the MoS2 to GO ratio, we can achieve a structure dominated by alternately stacked MoS2-GO nanosheets, which leads to improved filtration performances due to minimized swelling and restacking. One significant advantage of the heterogeneous MoS2-GO structure is its stability in aqueous environment. Unlike GO membranes, which can swell up to six times their original thickness, the heterogenous MoS2-GO membrane has shown minimum swelling, resulting in improved membrane selectivity. Additionally, the layer-stacked heterogeneity of the MoS2-GO structure mitigates the restacking problem inherent in pure MoS2 membranes when dried, which can lead to an irreversible loss of water permeability. In conclusion, our findings demonstrate that creating a heterogeneously stacked MoS2-GO membrane significantly improves both membrane stability and separation performances compared to homogenous pure GO or MoS2 membranes.