Strain Engineering of the NiTe/Ni₂P Heterostructure to Boost the Oxygen Evolution Reaction

Abstract

Discovering highly efficient and stable non-precious metal catalysts for the oxygen evolution reaction (OER) is crucial for energy conversion in water splitting. However, preparing high-performance OER catalysts and elucidating the structural changes in the process are still challenging. Herein, we synthesize the NiTe/Ni₂P heterostructure and demonstrate the strain engineering of NiTe/Ni₂P via the lattice incompatibility between the phosphide and the telluride. The strain engineering of the NiTe/Ni₂P heterostructure not only significantly boosts the OER activity but also effectively stabilizes the intrinsic structure of the catalyst after the OER process by using the <i>in situ</i>-produced metal salt as a protection layer. After the OER stability test, no oxyhydroxide phase is observed, and <i>in situ</i> Raman spectroscopy reveals that a voltage-dependent phase transition appears during the OER, which is different from most previously reported Ni-based catalysts, for which the generation of irreversible NiOOH occurs after the OER. Density functional theory calculations further reveal that the tensile strain of Ni₂P will inhibit the presence of irreversible phase transitions of Ni₂P into NiOOH due to the weak adsorption ability of the oxygen species caused by strain engineering. In short, this work opens a new gate for using strain nanotechnology to design high-performance OER catalysts.