Structural and transport phenomena of urocanate-based proton carrier in sulfonated poly(ether ether ketone) membrane composite by Nimmanpipug, Piyarat, Kodchakorn, Kanchanok, Lee, Vannajan Sanghiran, Yana, Janchai, Jarumaneeroj, Chatchai, Phongtamrug, Suttinun, Chirachanchai, Suwabun