Relationship between Hydrogen Evolution and Wettability for Multiscale Hierarchical Wrinkles.

Transition metal dichalcogenides (TMDs) are emerging two-dimensional materials with potential use for the hydrogen evolution reaction (HER) because they express a desired binding energy with protons. To date, TMD-based HER catalytic performance has been enhanced mostly by chemical modification, such as introducing defects, doping, and phase control. Herein, we enhanced the HER performance by precise control of wettability via hierarchical wrinkling. This hierarchical wrinkling confers tunability of the receding contact angle (2-30°) by controlling the wavelength of the hierarchical wrinkles. Minimization of the receding contact angle is directly related to overpotential reduction on the MoS2 wrinkles through gas detachment from the catalytic surface. Unlike in previous studies, in this work, we demonstrated the effect of wettability only without changing other parameters such as surface chemistry. We showed that our method can be applied to other TMD materials such as WS2. This study will contribute to future TMD-based catalyst applications, such as hydrogen evolution, CO2 reduction, and oxygen evolution.