Unraveling the poisoning mechanism of impurity gases on TiFe hydrogen storage alloy

TiFe alloy is a type of AB-based hydrogen storage material with unique characteristics and wide-ranging applications. However, the presence of impurity gases (such as O2, CO, CO2, and CH4 etc.) has a considerable impact on the hydrogen storage capacity and kinetics of the TiFe alloys, which drastically limits its practical application in hydrogen storage. Consequently, in this work, we have investigated the hydrogen absorption kinetics and cycling performance of TiFe0.9 alloy in the presence of these common impurity gases (including CH4, CO, CO2, and O2) and determined the corresponding poisoning mechanisms. Specifically, we found that CH4 does not react with the alloy and acts through physical coverage. In contrast, CO and CO2 occupy the active sites for H2, significantly impeding the dissociation and absorption of H2. Additionally, O2 reacts directly with the alloy, forming a passivating layer that prevents hydrogen absorption. These findings were further corroborated by in-situ fourier transform infrared spectrometer (FTIR) and density functional theory (DFT). Through DFT calculations obtained the relationship between the adsorption energies of impurity gases and hydrogen, complements the experimental results. Understanding these poisoning behaviors is crucial for designing Ti-based high-entropy hydrogen storage alloy alloys with enhanced resistance to poisoning.