Single-atom catalysts (SAC) have enabled high electrocatalytic activity production because of the enormous active sites bearing catalysts for hydrogen evolution reaction (HER). Herein, we report cerium single atom (Cesa) anchored silver selenide (Ag2Se) via metal-chalcogenide interaction for high-performance HER evolution. The designed electrocatalyst possesses extraordinary electrochemical and optical properties, thus the Cesa-Ag2Se could be a potential catalyst for the photo-electrochemical HER process. The sluggish diffusion rate of the Ce atom within the Ag2Se facilitates the high stability and the dispersed Cesa displayed ∼2 eV of energy differences with the Ce dimer proving the formation of dispersed Cesa over Ag2Se is potentially favorable. The minimum energy pathway (MEP) suggested the Cesa-Ag2Se system established only 0.003 eV as an ultra-low activation energy barrier in order to produce H2, which is by far the finest performance of Ag2Se-based thermodynamically favourable catalysis. The accumulated electron density due to the presence of Cesa enabled the presence of a large number of potential active sites (Ce and Ag) for hydrogen adsorption, in addition, the supportive zero band gap of the Ag2Se accelerated the kinetics for HER. Ultimately, we employed the Wentzcovitch cell dynamics-based molecular dynamics study for H* adsorbed Cesa-Ag2Se that suggests the stability of the catalyst for 500 fs. The in-depth HER modelling using the Lennard-Jones force field demonstrated the insightful dynamics behaviour of the catalytical system.