Still, the applications of soluble inorganics are limited since it easily elutes. Some research produced a membrane containing a large amount of insoluble inorganic particles by making them highly dispersed , . However, highly dispersed states do not easily coexist with beneficial morphology, a phase separation structure . In general, PEMs are composed of two phases: the hydrophilic phase for proton conduction and the hydrophobic phase for the stability of the membrane . For example, in membranes with high proton conductivity at high humidity, such as Nafion®, phase separation occurs and forms ion channels, creating continuous proton transfer pathways through the entire membrane . In contrast, the membrane includes fewer pathways under low humidity, decreasing conductivity. Therefore, high content of inorganics with the phase separation structure is vital to keep the sufficient proton transfer pathways.