Halophobic Prussian blue analogue electrodes for saturated saline water electrolysis

Continuous seawater electrolysis is efficient for green hydrogen production, but some key issues have been overlooked. For example, the accumulated to saturated NaCl in electrolyte is poison to cathode by covering its surface and available active sites. Herein we demonstrate Pt/NiFe Prussian blue analogue (Pt/NiFePBA) electrode can continuously catalyze hydrogen evolution effectively at −500 mA·cm⁻² in a 6 M NaOH electrolyte containing saturated NaCl, without being impeded by the formation of NaCl crystals on the electrode surface, which is in distinct contrast to commercial electrodes. Experimental results indicate that Fe(CN)₆⁴⁻ spontaneously released by Pt/NiFePBA blocks the traditionally preferred basal plane growth of NaCl along {100} facets, but favors its growth along {110} basal plane. This alteration leads to an increased crystallization difficulty of NaCl near the electrode, rendering it halophobic (anti-NaCl precipitation) property. This investigation should shed light on general salt involving process besides the practical implementation of seawater electrolysis.