• Ag substitution reduces the formation enthalpy of Mg2NiH4, weakening M–H bonds and lowering hydrogen desorption temperatures.
• The Mg1.95Ag0.05Ni alloy was successfully produced by vacuum arc melting and melt spinning, yielding ribbons with fast hydrogen exchange and high storage capacity.
• DFT and uMLIP simulations confirmed that Ag doping destabilizes the hydride phase, consistent with experimental observations.
• Multi-technique characterization (XRD, XPS, SEM, TEM, DTA, TGA, Sievert and electrochemical) links the structural modifications to improved hydrogen storage performance.