Sulfonated resorcinol-formaldehyde polymer gels synthesized in Nafion ion clusters as nanoscale reactors for a filler of hybrid proton exchange membranes

► Sulfonated RF polymer gels synthesized in Nafion ion clusters as nanoscale reactors. ► Uniform dispersion of the nano-sized polymer gels in Nafion matrix. ► The polymer gel/Nafion became a hybrid membrane for PEMFC. ► Greatly improved single-cell performance under non-humidifying feed conditions.