Exploring the Intrinsic Effects of Lattice Strain on the Hydrogen Evolution Reaction via Electric-Field-Induced Strain in FePt Films

Strain engineering has the potential to modify the adsorption process and enhance the electrocatalytic activity, especially in the hydrogen evolution reaction (HER). However, the introduction of lattice strain in electrocatalysts is often accompanied by a change in chemical composition, surface morphology, or phase structure to a certain extent, impeding the investigation of the intrinsic strain effect on HER. In this work, the FePt film was deposited on a Pb(Mg_1/3Nb_2/3)_0.7Ti_0.3O₃ (PMN-PT) substrate to construct the FePt/PMN-PT heterojunction, and the continuously adjustable nonvolatile lattice strain is induced by the asymmetric electric field manipulation avoiding the aforementioned disturbance factors. HER experimental results demonstrate a drastic improvement in the overpotential of FePt with the largest tensile strain of 3000 ppm, and the observed variation of HER performance indicates an upward trend as the tensile strain increases. Density functional theory calculations reveal that the Gibbs free energy of FePt with the appropriate tensile strain is closer to zero, attributed to the downward shift of the d-band center. Our study provides an approach to continuously regulate the lattice strain with less interference factors, facilitating the exploration of the intrinsic strain effect on a wide range of catalysts.