Solution-Phase Intercalation of 2D Hybrid SGO in Sulfonated Poly(2,6-dimethyl-1,4-phenylene oxide): Improved Electrochemical Properties and Electrodialytic Desalination Performance

This work investigates a strategy to overcome conventional trade-offs of long-range ionic conductivity in pristine sulfonated poly(2,6-dimethyl-1,4-phenylene oxide) (SPPO-S) via solution-phase intercalation of synthesized hybrid sulfonated graphene oxide (hSGO) in an SPPO-S matrix. The hSGO nanocomposite was prepared via covalent functionalization of GO through facile silyl-oxy bond formation using 3-mercaptopropyl trimethoxy silane (MPTMS). A series of nanocomposite membranes (ShGO) with low (0.1, 0.2, 0.5, 0.8 wt %) to high (1.0, 2.0, 5.0 wt %) hSGO concentrations were fabricated, and the influence of hSGO on physicochemical and electromembrane transport properties was evaluated. XPS and ζ-potential measurements illustrated that the hydrophilic hSGO with a spacer-type trimethylene sulfonic acid [(−CH2)3–SO3H] moiety establishes a dynamic interaction via means of intermolecular H-bonding and short-range electrostatic interactions, respectively. With 0.5 wt % hSGO, the membranes showed excellent physicochemical attributes (i.e., IEC = 1.24 mequiv g–1 and WU = ∼44%) with improved ionic conductivity by ∼43% (i.e., κm = 1.92 × 10–2 S cm–1) in contrast to pristine SPPO-S (i.e., IEC = 0.98 mequiv g–1; WU = 37.12%; κm = 1.34 × 10–2 S cm–1). Chemical structures and phases were confirmed using NMR, FT-IR, XRD, XPS, etc. The i–V characteristics illustrated that the high Ilim1 of nanocomposite membranes alleviated the ion percolation and influenced the operational potential to a broader range for lower power consumptions (PCs) and higher current efficiencies (CEs). ShGO-0.5 showed PC as low as 1.04 kWh kg–1 and CE as high as ∼88% during electrodialytic brackish water desalination. In summary, the prepared membranes may be promising candidates for electrodialytic brackish water desalination with a high salt removal (≥93%) efficiency.