Ultraefficient Electrocatalytic Hydrogen Evolution from Strain-Engineered, Multilayer MoS 2 .

This paper reports an approach to repurpose low-cost, bulk multilayer MoS 2 for development of ultraefficient hydrogen evolution reaction (HER) catalysts over large areas (>cm 2 ). We create working electrodes for use in HER by dry transfer of MoS 2 nano- and microflakes to gold thin films deposited on prestrained thermoplastic substrates. By relieving the prestrain at a macroscopic scale, a tunable level of tensile strain is developed in the MoS 2 and consequently results in a local phase transition as a result of spontaneously formed surface wrinkles. Using electrochemical impedance spectroscopy, we verified that electrochemical activation of the strained MoS 2 lowered the charge transfer resistance within the materials system, achieving HER activity comparable to platinum (Pt). Raman and X-ray photoelectron spectroscopy show that desulfurization in the multilayer MoS 2 was promoted by the phase transition; the combined effect of desulfurization and the lower charge resistance induced superior HER performance.