Unitized reversible fuel cells (URFC) combine the functionality of a fuel cell and electrolyzer in one unitized device. For a URFC with proton exchange membrane, the Ti-felt is applied to the GDL substrate at the oxygen electrode, and responsible for an optimum humidification state and liquid water distribution in the catalyst layer during both operations of a fuel cell and an electrolysis. The experimental result indicates that the loading PTFE on the Ti-felt substrate brings a negative effect on the mass transport of liquid and gas during the fuel cell operation and no effect on the electrolysis performance. The larger fiber diameter of Ti-felt brings better performance of the fuel cell, whereas the electrolysis performance is degraded.