Centimeter-Scale Two-Dimensional Metallenes for High-Efficiency Electrocatalysis and Sensing

Two-dimensional (2D) metals have received considerable attention in recent years because of their fascinating physical and chemical properties, as well as potential applications in electrocatalysis, sensors, plasmonics, etc. However, the fabrication of 2D metals, especially atomically thin ones with large lateral size, remains a significant challenge because of the strong and isotropic metallic bonds. Here, we use Pt as a model system and demonstrate a general way to fabricate freestanding, high-quality 2D metals with giant aspect ratios (as large as ∼10⁷) and controllable thickness down to 1 nm via a combination of room-temperature physical deposition and chemical etching. The cool deposition could suppress the Volmer-Webber growth mode, resulting in the formation of continuous ultrathin Pt with smooth surface and high conductivity. Moreover, the ultrathin 2D Pt exhibit outstanding hydrogen evolution reaction activity with a mass activity of 8.06 mA μg^-1 at 0.06 V, ∼18 times higher than that of the commercial Pt/C catalyst. Additionally, the freestanding Pt-based strain sensor exhibits a high gauge factor of up to ∼4643, which is 3 orders of magnitude higher than that of conventional constantan wire-based strain gauges. Our studies pave the way for further developing wafer-scale 2D metal-based devices for various applications.