Alloy-strain-output induced lattice dislocation in Ni3FeN/Ni3Fe ultrathin nanosheets for highly efficient overall water splitting

Abstract

Designing highly efficient, stable and low-cost bifunctional electrocatalysts based on in situ microstructure evolution, especially achieving partial lattice dislocation on a highly crystalline texture, to catalyze the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is challenging. Herein, catalysts with the Ni₃Fe alloy embedded in Ni₃FeN ultrathin nanosheets (∼1 nm) were fabricated through thermal ammonolysis treatment of cation-vacant monolayered NiFe layered double hydroxides. The emergence of the Ni₃Fe alloy during the annealing process unavoidably leads to strain output to adjacent microstructures in ultrathin nanosheets, contributing to the formation of lattice dislocations. Such lattice defects, combining the ultrathin 2D morphology and synergistic interfacial effect between Ni₃FeN and Ni₃Fe, endow the electrocatalyst (d-Ni₃FeN/Ni₃Fe) with excellent electrocatalytic performance for both the OER and HER in alkaline media, requiring overpotentials of 250 mV and 125 mV to drive a current density of 10 mA cm⁻² in 1 M KOH, respectively. The water electrolyzer with d-Ni₃FeN/Ni₃Fe as the cathode and anode yields a current density of 10 mA cm⁻² at a low cell voltage of 1.61 V, and exhibits excellent durability of over 90 h, outperforming the commercial IrO₂‖Pt/C cell. The present study offers a new trial of lattice defect engineering to develop high-performance non-precious bifunctional electrocatalysts for overall water splitting.