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

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 ΔG_H 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.