Water scarcity presents a critical challenge to global sustainable development. Membrane distillation (MD) is a promising

technology for desalination, yet its performance is often limited to the properties of the hydrophobic membrane. 

This study reports a facile in-situ reduction strategy to fabricate reduced graphene oxide (RGO)-polyvinylidene fluoride 

(PVDF) composite membranes for enhanced direct contact MD (DCMD). The composite membranes were designed for 

robust desalination and potential treatment of hypersaline wastewater. Hydrazine hydrate was employed as the reducing 

agent within the PVDF casting solution to simultaneously induce phase inversion and the reduction of GO to RGO. The 

effects of RGO loading on membrane properties were systematically investigated. The optimized membrane (R-4, with 

a GO precursor concentration of 9 g/L) exhibited a water contact angle of 105.13°, a liquid entry pressure of 2.05 bar, 

and a high permeate flux of 11.21 kg·m–2·h–1 when treating a 3.5 wt % NaCl solution at 60 °C, representing a 1.46-fold 

flux enhancement over a commercial PVDF membrane while maintaining stable salt rejection>99.9% during a 336-hour 

test. The improved performance is attributed to the synergistic effect of RGO, which simultaneously enhanced membrane 

hydrophobicity, refined the pore structure towards a more uniform distribution. This work demonstrates the great potential

of the in-situ reduction strategy for developing high-performance and robust MD membranes for water treatment 

applications.