The emergence of monolayer two-dimensional (2D) materials revolutionizes the strategies of advancing the modern technologies. Semiconducting 2D materials such as MoS2, WS2, MoSe2, and WSe2 especially act as a propeller aiming to accelerate and expand the research of catalyst, battery, and electronics. Hydrogen evolution reaction (HER) is fundamentally important for various electrochemical processes, such as fuel cells and H2 production, particularly for the replacement of precious metal catalysts, Pt. Plus, the needs of energy storage and the emphatic requirements of fast charging are rising with the advancement of microprocessor technologies. The bulk form MoS2 is a poor HER catalyst and shows negligible capacitance, however, monolayer MoS2 exhibits extraordinary performance in both HER and energy storing capability. Through a modified top-down process to isolate individual monolayer flakes of MoS2 incorporating with a one-step direct printing technique the exposed surface area can be maximized and immediately exploited as a catalyst for stably producing H2 in both acidic and basic solutions and even at extreme radiative environments. Furthermore, individual monolayer MoS2 flakes can as well be collected and stored as a powder form which remain the free-standing quality giving rise to the significance of creating 3D monolayer flakes containing inks for inkjet printing which results in an enhanced capacitance in supercapacitors. In addition, the advancement of the miniaturization of silicon transistors is approaching the inevitable physical limits in the gating channel because of the short channel effect which is the primary concern to cease Moore’s law. Monolayer semiconductors offer dangling-bonds-free atomically thin and flat surface which is desirable as channel materials in transistors. Although the mass producibility of top-down process provides promising prospect in catalyst and battery applications the control of the uniform thickness on a large scale is extremely difficult. Chemical vapor deposition (CVD) and sapphire wafer is one of the most reliable bottom-up processes for the mass production of wafer-scale 2D semiconducting films in the manufacturing lines with the lowest costs and highest throughputs. An approach of epitaxially growing single-crystal 2D semiconducting films is elucidated to achieve the state-of-the-art crystallographical and electrical uniformity on 2-inch sapphire wafers.