Highly hydrophilic polybenzimidazole/Zirconia composite separator with reduced gas crossover for alkaline water electrolysis

Porous separators have been widely used in alkaline water electrolyzers (AWEs). To solve the problem of high gas permeability and stability caused by the large pores and poor compatibility of commercial Zirfon separators, it is important to develop a diaphragm with high OH conductivity, high bubble point pressure, low area resistance, and low hydrogen permeability for alkaline electrolyzers. Here, we proposed highly hydrophilic polybenzimidazole-type composite porous separators with specific sponge-like pores via nonsolvent-induced phase separation. The high hydrophilicity of poly(2, 2'-(1, 4-naphthalene)-5, 5'-dibenzimidazole) (NPBI) and ZrO2 enhanced the interfacial interaction to prevent filler overflow. Compared to the Zirfon separator, the area resistance and hydrogen permeability of the proposed separators were significantly reduced. The Z60 diaphragm exhibited a higher water absorption rate (62.2%) and KOH liquid absorption rate (23.5%), lower area resistance (0.162 Omega cm(2)), higher bubble pressure (4.48 bar), and lower hydrogen permeability (2.63 L min 1 center dot cm 2). Moreover, the voltage of the Z60 diaphragm was 2.007 V at 0.5 A/cm(2) in 6 M KOH, which is comparable to commercial Zirfon. The Z60 separator used for AWEs with Ni foam catalysts obtained an excellent long-term stability of up to 400 h with a voltage fluctuation of only 55 mu V/h. Therefore, the design of the NPBI/ZrO2 porous composite diaphragm provides a new idea for the development of high-performance alkaline water electrolysis.

Automated summary

To solve the problems of high gas permeability and stability caused by commercial Zirfon separators, a highly hydrophilic polybenzimidazole-type composite porous separator was proposed. Compared to Zirfon separators, the proposed separators exhibited significantly reduced area resistance and hydrogen permeability, as well as higher water and liquid absorption rates, bubble pressure, and lower hydrogen permeability.