Electronic Structure Regulation by Fe Doped Ni-Phosphides for Long-term Overall Water Splitting at Large Current Density.

Acquiring a highly efficient electrocatalyst capable of sustaining prolonged operation under high current density is of paramount importance for the process of electrocatalytic water splitting. Herein, Fe-doped phosphide (Fe-Ni 5 P 4 ) derived from the NiFc metal-organic framework (NiFc-MOF) (Fc: 1,1'-ferrocene dicarboxylate) shows high catalytic activity for overall water splitting (OWS). Fe-Ni 5 P 4 ||Fe-Ni 5 P 4 exhibits a low voltage of 1.72 V for OWS at 0.5 A cm -2 and permits stable operation for 2700 h in 1.0 m KOH. Remarkably, Fe-Ni 5 P 4 ||Fe-Ni 5 P 4 can sustain robust water splitting at an extra-large current density of 1 A cm -2 for 1170 h even in alkaline seawater. Theoretical calculations confirm that Fe doping simultaneously reduces the reaction barriers of coupling and desorption (O * →OOH * , OOH * →O 2 * ) in the oxygen evolution reaction (OER) and regulates the adsorption strength of the intermediates (H 2 O * , H * ) in the hydrogen evolution reaction (HER), enabling Fe-Ni 5 P 4 to possess excellent dual functional activity. This study offers a valuable reference for the advancement of highly durable electrocatalysts through the regulation derived from coordination frameworks, with significant implications for industrial applications and energy conversion technologies.