Abstract: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 alloy, with its remarkable hydrogen storage capacity, cost-effectiveness, and mild conditions for hydrogen absorption and desorption, presents a promising solution to the challenges associated with high costs and safety concerns associated with 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 Cu and other elements co-doped in TiFe alloy can enhance their activation properties, the mechanism by which Cu affects the hydrogen storage properties of TiFe alloys remains unclear. In this study, employing density functional theory (DFT) calculations, systematically investigates 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 reduce the adsorption energy of H2 on the alloy surface from −2.93 eV to −3.13 eV, and decrease its 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 activation performance tests and isothermal hydrogen storage tests were conducted to validate the theoretical predictions. 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, the maximum hydrogen storage and hydrogen absorption kinetics of the alloys did not decrease under these conditions, which is consistent with the theoretical calculations. Close-