Fig. 4: The performance of MFE in overall water splitting.

a A typical operation sequences during the cyclic test, the H2 purity was determined at the time with the red dots; the influence of b current densities, c temperature, and d flow rate on the potential bias, other than specified, current density is 750 mA cm−2, temperature is 35 °C and flow rate is 50 ml min−1, anolyte/catholyte swap is not applied for simplicity. Both anolyte and catholyte are 1.0 M KOH solutions.