Influences of a bipolar membrane and an ultrasonic field on alkaline water electrolysis

The energy efficiency of alkaline water electrolysis improved by using the polyvinylidene fluoride-grafted 2-methacrylic acid 3-(bis-carboxymethylamino)-2-hydroxyl-propyl ester bipolar membrane (PVDF-g-G-I BM) as diaphragms with an ultrasonic field (USF) has been explored in this study. The PVDF-g-G-I BM was prepared by the plasma-induced polymerization method. The method utilized the porous PVDF membrane as substrates, and G-I monomer was grafted onto both sides of the PVDF membrane after plasma treatment. The performance of the PVDF-g-G-I BM was demonstrated by measuring the cell voltage for the cell operated with or without an USF. According to steady-state E–I curves, the order of the cell voltage for alkaline water electrolysis was the DuPont commercial membrane > Water > PVDF-g-G-I BM under the same working condition. The PVDF-g-G-I BM was found to function well as a diaphragm in alkaline water electrolysis. In comparison with Water without an USF, the H2 production efficiency by using the PVDF-g-G-I BM was improved 5–16/4% and an energy saving of ca. 15–20% (13–18%)/8–12% (6–10%) can be reached in alkaline water electrolysis at 0.5 M (1.0 M) NaOH for the cell operated with/without an USF, respectively.