Polyvinylidene fluoride-based modified membranes for hydrogen generation by direct seawater electrolysis and proton exchange membrane fuel cells

A polyvinylidene fluoride (PVDF) modified proton exchange membrane (PEM) bearing high sulfonic acid density was designed and investigated for water electrolysis application and H₂–O₂ fuel cell performance. The fabrication method involved ozonation of PVDF, followed by grafting using p-benzoquinone (i.e., Quino-PVDF) and successive sulfonation of Quino-PVDF to acquire the sulfonated Quino-PVDF copolymer. Moreover, a blending modification employing the Nafion™ ionomer was employed to enhance the performance of sulfonated Quino-PVDF based cation exchange membranes (i.e., QuinoCEMs). The membrane with 25 wt/wt% Nafion™/sulfonated Quino-PVDF (i.e., QuinoCEM-0.25) showed good performance in vapor-phase water electrolysis, liquid water electrolysis and direct seawater and achieved maximum current densities of 130, 480 and 240 mA cm⁻² over a cell voltage of 1.8 V at 80 °C respectively. Furthermore, the QuinoCEM-0.25 based membrane electrode assembly achieved a peak power density of 400 mW cm⁻², comparable to that of Nafion-212™ (i.e., 412 mW cm⁻²) in proton exchange membrane fuel cells (PEMFCs). Thus, this study highlights the potential of modified PVDF proton exchange membranes as efficient and cost-effective alternatives to commercially available PEMs.