High performance and eco-friendly chitosan hydrogel membrane electrolytes for direct borohydride fuel cells

► Ionically crosslinked chitosan hydrogel membrane electrolytes (ICCSHMEs) are studied. ► Na2SO4 and Na2HPO4 were used as cross-linking agents in the preparation of ICCSHMEs. ► The ICCSHMEs were employed in direct borohydride fuel cells (DBFCs). ► HPO42−-based ICCSHME showed better performance than SO42−-based ICCSHME in DBFC. ► HPO42−-based ICCSHME showed a maximum peak power density of ≈810 mW cm−2 at 70 °C.