Strain-Enabled Local Phase Control in Layered MoTe₂ for Enhanced Electrocatalytic Hydrogen Evolution

Electrocatalytic water splitting produces hydrogen fuel, but its dependence on expensive platinum-based electrocatalysts has limited industrial-scale implementation. Here, we report an approach for the activation of electrochemically inert layered MoTe₂ that results in a low-cost, scalable, and readily available hydrogen evolution reaction (HER) catalyst for water splitting. This approach relies on the transfer of mechanically exfoliated MoTe₂ flakes to gold thin films on prestrained thermoplastic substrates. By relieving the prestrain, a tunable level of internal tensile strain is developed in the flakes as a result of spontaneously formed surface wrinkles, resulting in a local semiconductor-to-metal phase transition to form phase boundaries. This strain engineering enhances the HER performance of the MoTe₂ with reduced charge transfer resistance, and in operando activation of the flakes further amplifies the electrochemical activity, rivaling that of platinum. Density functional theory calculations provide fundamental insight into how strain-induced heterophase boundaries promoted HER activity.