Construction of Sulfonated Carbon Nanoflowers for Efficient Proton Transportation of the Proton Exchange Membrane

Sulfonated carbon nanoflowers (SCNFs) were prepared by carbonizing polyacrylonitrile (PACN) as carbon nanoflowers (CNFs) and subsequent sulfonation of CNF. By integration of SCNF with a Nafion matrix, a hybrid membrane was constructed, which exhibited effectively enhanced proton conducting and methanol blocking abilities. Benefiting from the highly rough surface and multidirectional channels of SCNF as well as abundant interaction sites between SCNF and Nafion, the proton conduction pathways were well regulated and optimized in the hybrid membrane. The proton conductivity of the hybrid membrane achieved was 0.260 S cm–1 at 90 °C and 95% RH, which was ∼0.8-fold higher than that of the pristine Nafion membrane (RN). Additionally, the methanol permeability of the SCNF/RN membrane reduced to 10.91 × 10–8 cm2 s–1 from 28.41 × 10–8 cm2 s–1 of RN, which mainly ascribed to an increased meandering degree of methanol permeation in the membrane caused by the barrier function of SCNF. Besides, the single direct methanol fuel cell (DMFC) using the hybrid membrane afforded a power output of 30.8 mW cm–2, ∼153% that of the single-cell using RN (20.1 mW cm–2). This study furnishes a worthy strategy to construct 3D functional carbon nanomaterials for fabricating a proton exchange membrane with a brilliant overall performance.