Transition metal dichalcogenides (TMDs) have emerged as a focal point in electrocatalysis, particularly for the hydrogen evolution reaction (HER), owing to their notable catalytic activity, chemical stability, and cost-efficiency. Despite these advantages, the challenge of devising a practical and economical method for their large-scale application in HER remains an unresolved and critical issue. In this study, a facile, scalable, and cost-effective approach is introduced for producing high-yield, catalytically active TMD nanoparticles, including MoS₂, MoSe₂, RuS₂, and RuSe₂. These nanoparticles are synthesized through an aqueous room-temperature process, which is not only environmentally friendly but also economically feasible for large-scale production. Remarkably, these TMD nanoparticles exhibit versatile catalytic activity across a broad pH range for HER. Among them, RuSe₂ nanoparticles demonstrate catalytic performance comparable to that of a commercial Pt/C electrode. Upon scaling up, the nanomaterials show great potential for integration into practical proton exchange membrane water electrolyzers, maintaining high efficiency even at large current densities and exhibiting very stable performance for up to 100 h. This research paves the way to a sustainable synthesis method of high-performance catalysts, tailored for industrial hydrogen production applications.