The rapid progress in graphene research has led to intensive exploration of novel 2D materials. In particular, transition metal chalcogenides with layered structures have received significant attention because they offer many opportunities for fundamental and technological research in a variety of fields, including catalysis, energy storage, sensing, and electronic devices. In this talk, I first demonstrate how to prepare various transition metal chalcogenides/reduced graphene oxide (rGO) composites such as VS4/rGO, CoS2/rGO, and WS2/rGO by a simple hydrothermal method. And, I introduce that VS4/rGO and WS2/rGO and CoS2/rGO can be promising functional materials for Li storage and hydrogen evolution, respectively. Lastly, I show the fabrication of membrane electrode assembly (MEA) using high crystalline CVD-grown graphene or h-BN film as a proton exchange membrane. This work take a step forward for replacing the Nafion film with h-BN or graphene in the proton exchange membrane fuel cell (PEMFC).