Modulation of Inverse Spinel Fe3 O4 by Phosphorus Doping as an Industrially Promising Electrocatalyst for Hydrogen Evolution.

Abstract

Fe-based oxides have been seldom reported as electrocatalysts for the hydrogen evolution reaction (HER), limited by their weak intrinsic activity and conductivity. Herein, phosphorus doping modulation is used to construct inverse spinel P-Fe3 O4 with dual active sites supported on iron foam (P-Fe3 O4 /IF) for alkaline HER with an extremely low overpotential of 138 mV at 100 mA cm-2 . The obtained inverse spinel Fe-O-P derived from controllable phosphorization can provide an octahedral Fe site and O atom, which bring about the unusual dissociation mechanisms of two water molecules to greatly accelerate the proton supply in alkaline media. Meanwhile, the ΔGH of the P atom in Fe-O-P as an active site is theoretically calculated to be 0.01 eV. Notably, the NiFe LDH/IF(+) ||P-Fe3 O4 /IF(-) couple achieves an onset potential of 1.47 V (vs RHE) for overall water splitting, with excellent stability for more than 1000 h at a current density of 1000 mA cm-2 , and even for 25 000 s at 10 000 mA cm-2 in 6.0 m KOH at 60 °C. The excellent catalyst stability and low-cost merits of P-Fe3 O4 /IF may hold promise for industrial hydrogen production. This work may reveal a new design strategy of earth-abundant materials for large-scale water splitting.