“…The developments focused on replacing or decreasing the cost and increasing the selectivity of commercial membranes in two ways: (i) including the different characteristic properties of polymer materials or inorganic nanofillers in the PFSA polymer matrix without significantly affecting the overall performances [ 81 , 82 , 83 , 84 , 85 , 86 ], and (ii) searching for alternative polymer membranes with and without the addition of functional groups, polymers, inorganic fillers, and/or cross-linkers as a blend, composite, or cross-linked membranes [ 87 , 88 , 89 , 90 , 91 , 92 , 93 , 94 ]. There are different kinds of synthetic polymers, such as sulfonated poly(ether ether ketone) [ 91 , 95 , 96 ], sulfonated polysulfone [ 97 ], sulfonated poly(vinylidene fluoride) [ 98 ], polytetrafluoroethylene [ 99 ], and poly(phenylene oxide) [ 100 ] that have been studied to improve the performances of DMFC. In addition, different blend membranes, composite membranes, grafted membranes, and cross-linked membranes have been established for DMFC.…”