Exploring the Intrinsic\nEffects of Lattice Strain\non the Hydrogen Evolution Reaction via Electric-Field-Induced Strain\nin FePt Films

Strain engineering has the potential to modify the adsorption\nprocess\nand enhance the electrocatalytic activity, especially in the hydrogen\nevolution reaction (HER). However, the introduction of lattice strain\nin electrocatalysts is often accompanied by a change in chemical composition,\nsurface morphology, or phase structure to a certain extent, impeding\nthe investigation of the intrinsic strain effect on HER. In this work,\nthe FePt film was deposited on a Pb(Mg<sub>1/3</sub>Nb<sub>2/3</sub>)<sub>0.7</sub>Ti<sub>0.3</sub>O<sub>3</sub> (PMN–PT) substrate\nto construct the FePt/PMN–PT heterojunction, and the continuously\nadjustable nonvolatile lattice strain is induced by the asymmetric\nelectric field manipulation avoiding the aforementioned disturbance\nfactors. HER experimental results demonstrate a drastic improvement\nin the overpotential of FePt with the largest tensile strain of 3000\nppm, and the observed variation of HER performance indicates an upward\ntrend as the tensile strain increases. Density functional theory calculations\nreveal that the Gibbs free energy of FePt with the appropriate tensile\nstrain is closer to zero, attributed to the downward shift of the\nd-band center. Our study provides an approach to continuously regulate\nthe lattice strain with less interference factors, facilitating the\nexploration of the intrinsic strain effect on a wide range of catalysts.