Strain-Enabled Band Structure Engineering in Layered PtSe₂ for Water Electrolysis under Ultralow Overpotential

This paper describes a simple design methodology to develop layered PtSe₂ catalysts for hydrogen evolution reaction (HER) in water electrolysis operating under ultralow overpotentials. This approach relies on the transfer of mechanically exfoliated PtSe₂ flakes to gold thin films on prestrained thermoplastic substrates. By relieving the prestrain, a tunable level of uniaxial internal compressive and tensile strain is developed in the flakes as a result of spontaneously formed surface wrinkles, giving rise to band structure modulations with overlapped values of the valence band maximum and conduction band minimum. This strain-engineered PtSe₂ with an optimized level of internal tensile strain amplifies the HER performance of the PtSe₂, with performance far greater than that of pure platinum due to significantly reduced charge transfer resistance. Density functional theory calculations provide fundamental insight into how strain-induced band structure engineering correlates with the promoted HER activity, especially at the atomic edge sites of the materials.