Highly hydrophilic TiO2/Chitosan composite separator with low area resistance for achieving efficient alkaline water electrolysis

• The composite separator features both low area resistance (0.18 Ω cm 2 in 6M KOH) and high bubble point pressure (3.42 bar). • Current density over 1.5A cm −2 achieved at 1.84V@80°C, and electrolyzers afforded long-life span in exceeding 360h. • Chitosan enhanced the hydrophilicity of the composite separator. • The coupling performance between the composite separator and solar energy has been studied. Alkaline water electrolysis is widely regarded as an efficient route for producing green hydrogen. However, in alkaline systems, commercial separators typically exhibit low bubble point pressure and high area resistance, which can result in inefficiencies and safety issues. This study presents a porous composite separator based on polysulfone and supported by polyphenylene sulfide. By incorporating TiO 2 nanoparticles and chitosan, finger-like ion-conductive channels conducive to hydroxide ion transport were constructed. The optimally formulated separator exhibited favorable hydrophilicity, a decreased area resistance of 0.18 Ω cm 2 and an elevated bubble point pressure of 3.42 bar, demonstrating its improved performance in comparison to the commercial Zirfon separator. Electrochemical evaluations demonstrated that under conditions of 80°C and 6 M KOH, the optimally proportioned separator exhibited a voltage of 1.84 V at 1.5 A cm −2 . Importantly, the diaphragm demonstrated outstanding operational stability exceeding 360 hours. This novel separator combines low resistance, high bubble point pressure and good durability. The results of this study present a novel strategy to address the poor gas barrier properties of traditional polyphenylene sulfide fabric separators and the inadequate hydrophilicity of polysulfone separators.