Hydrogen energy, recognized as a high-calorific, clean and carbon-free secondary energy source, plays a pivotal role in achieving the "dual-carbon goal". TiFe alloys, with their remarkable hydrogen storage capacity, cost-effectiveness, and mild conditions for hydrogen absorption and desorption, present a promising solution to the challenges of high costs and safety concerns in hydrogen storage and transportation technologies. However, the pronounced oxygen sensitivity of TiFe alloys renders them highly susceptible to oxygen poisoning, leading to the formation of a dense passivation layer on the alloy surface. Despite extensive research indicating that co-doping TiFe alloys with Cu and other elements can enhance the alloy's activation properties, the mechanism by which Cu affects their hydrogen storage properties remains unclear. In this study, we systematically investigate, using density functional theory (DFT) calculations, the role of Cu in modulating the formation of the surface oxide layer on TiFe alloys, and its impact on the hydrogen storage process when Cu substitutes Fe. The results demonstrate that Ti atoms exhibit a strong oxygen affinity, and during the oxidation process, they preferentially form dense titanium oxides. Upon Cu substitution, the continuity of the oxide layer on the alloy surface is significantly reduced, which leads to a decrease in titanium oxide content. Ab initio molecular dynamics (AIMD) simulations reveal that Cu significantly reduces the motion velocity of Ti atoms along the z-axis (from 0.368 Å/ps to 0.182 Å/ps at 150 fs in the forward direction), while the motion velocity of Fe atoms around Cu is notably accelerated, increasing the likelihood of the formation of less dense Fe oxides. These findings suggest that Cu can effectively inhibit the growth of the oxide layer and mitigate its densification. Furthermore, at the microscopic level, Cu can enhance H2 adsorption by lowering the adsorption energy from −2.93 eV to −3.13 eV, and decrease the dissociation energy barrier. Additionally, Cu optimizes the H atom diffusion channel on the surface, reducing the diffusion energy barrier by 64%, thereby enhancing the hydrogen absorption process in TiFe alloys. To validate the theoretical predictions, TiFe and TiFe0.9Cu0.1 alloys were synthesized by the vacuum melting method, and subjected to activation performance and isothermal hydrogen storage tests. Experimental results confirm that Cu reduces the number of activation cycles required for complete activation of TiFe alloys from five to three, significantly enhancing their activation characteristics. Notably, neither the maximum hydrogen storage capacity nor the hydrogen absorption kinetics of the alloys decreased under these conditions, which is consistent with the theoretical calculations.