Synergistic electronic modulation and Cl- shielding of Fe sites for robust seawater electrolysis

Abstract

Enhancing the performance of the oxygen evolution reaction (OER) is crucial for improving the overall efficiency of hydrogen production through seawater electrolysis. However, seawater electrolysis imposes stringent requirements on catalyst’s catalytic activity and corrosion resistance. Herein, we present a Ce-NiFeOOH/PO43- electrocatalyst exhibiting exceptional catalytic activity and chloride-corrosion resistance for direct seawater splitting. On one hand, the unique 4f orbitals of the rare earth element Ce cause a reconstruction of the electronic environment at the active sites of the NiFeOOH, enhancing catalytic activity. On the other hand, the phosphate groups provide charge shielding to prevent the electrode from being etched by Cl- in seawater and thereby enhancing the stability of Ce-NiFeOOH/PO43-. Electrochemical tests show that the catalyst can operate stably for 800 h at 0.5 A cm-2 in seawater. When the catalyst is integrated into an anion exchange membrane electrolyzer for seawater electrolysis, Ce-NiFeOOH/PO43- only requires 1.68 V to achieve 0.5 A cm-2. The electrolyzer achieves an efficiency of 74.6% and a hydrogen production cost of $0.897 per GGE H2 at 0.5 A cm-2, superior to the U.S. Department of Energy targets of 65% efficiency and $2 per gallon of gasoline equivalent (GGE) H2 by 2026. This work provides new insights into designing efficient and robust catalysts for green hydrogen production using seawater.