儲氫表現方面，由於沉澱物產生的表面裂縫，Ti5.5V0.65Fe3.7Ce0.15與Ti5.2V0.64Fe3.5Cu0.5Ce0.14將活化條件從Ti6Fe4所需的300 ℃、3 MPa降低至室溫、2 MPa，並將所需程序由兩次循環縮短為一次循環。活化後，Ti6Fe4展現1.85 wt.%的儲氫量，略高於傳統TiFe合金的1.8 wt.%，同時將吸氫平台壓力由4 MPa降低至0.3 MPa。Ti5.5V0.65Fe3.7Ce0.15則進一步提升儲氫量，達到2.2 wt.%，並因為V的作用，此合金僅有著單一平台壓。在1 MPa下，Ti5.5V0.65Fe3.7Ce0.15展現出優異的吸氫動力學，可在100秒內達到最大儲氫量，相較之下Ti6Fe4則需要30分鐘。這是因為由富含V的擴散通道提供的大量摻雜位點和連續開放的通道造成的結果。Ti5.2V0.64Fe3.5Cu0.5Ce0.14的吸氫動力學與Ti5.5V0.65Fe3.7Ce0.15相近，但因為銅較低的氫親和力，其儲氫量略降至1.98 wt.%。當儲氫溫度提高時，Ti5.5V0.65Fe3.7Ce0.15的可逆儲氫量減少較小，僅下降0.08 wt.%，而Ti6Fe4則下降0.40 wt.%。此外，由於添加Cu可進一步促進應力釋放，Ti5.2V0.64Fe3.5Cu0.5Ce0.14的可逆容量反而增加0.10 wt.%。而在循環測試中，Ti5.5V0.65Fe3.7Ce0.15與Ti5.2V0.64Fe3.5Cu0.5Ce0.14在50次循環後，除了第一次循環後被困在TiV氫化物中的氫氣，僅衰退了低於5%的儲氫量。整體而言，這些設計合金證明了成分調控能有效降低活化難度、提升儲氫容量，並優化平台壓力範圍，同時維持良好的循環穩定性，展現其於實際應用中的潛力。;Fossil fuel depletion and climate change have increased the demand for clean energy alternatives. Hydrogen energy is a promising candidate owing to its high energy density， resource abundance， and zero carbon emissions upon combustion. However， hydrogen storage remains a challenge. Compressed gas tanks pose explosion risks， while liquefied hydrogen requires energy to prevent boil-off. In contrast， metal hydrides are cost-effective， safe， and they possess the highest volumetric hydrogen density， making them a potential alternative for hydrogen storage. This study aims to optimize the activation and hydrogenation performance of TiFe-based alloys by tuning their compositions. The designed alloys are Ti6Fe4， Ti5.5V0.65Fe3.7Ce0.15， and Ti5.2V0.64Fe3.5Cu0.5Ce0.14. By introducing excess Ti， the absorption pressure was reduced， and a interdendritic region was formed. V substitution was used to modify the plateau behavior， resulting in a single and elongated plateau， while further reducing the plateau pressures. Ce was added to reduce activation difficulty and suppress TiFe oxide phases. Cu was introduced to adjust the absorption pressure to a more appropriate range and to relieve lattice strain energy， with the aim of improving cycling durability.
Characterization using field emission-electron probe microanalyzer (FE-EPMA) revealed a dendritic structure composed of TiFe and Ti-rich phases in the Ti6Fe4 alloy. In Ti5.5V0.65Fe3.7Ce0.15 and Ti5.2V0.64Fe3.5Cu0.5Ce0.14， V was dispersed throughout the alloy， especially in the Ti-rich phase， while Ce- and Cu-containing precipitates were observed on the surface. X-ray diffraction (XRD) results confirmed that the alloys maintained a body-centered cubic (BCC) structure after modification. In addition， the oxide phase changed from TiFe oxide to Ce oxide， accompanied by surface cracks in Ti5.5V0.65Fe3.7Ce0.15 and Ti5.2V0.64Fe3.5Cu0.5Ce0.14， which likely facilitated hydrogen diffusion. In contrast， Ti6Fe4 exhibited no obvious surface cracks.
In terms of hydrogenation performance， Ti5.5V0.65Fe3.7Ce0.15 and Ti5.2V0.64Fe3.5Cu0.5Ce0.14 reduced the activation requirement from 300 ℃ under 3 MPa for Ti6Fe4 to room temperature under 2 MPa， while shortening the required process from two cycles to one cycle due to the surface cracks generated by the precipitates. After activation， Ti5.5V0.65Fe3.7Ce0.15 showed the biggest improvement in storage capacity， reaching a capacity of 2.2 wt.% with single plateau thanks to smoothing effect of V， and completing absorption within 100 s under 1 MPa， compared with the 30 min required for Ti6Fe4. This is because of the abundant interstitial sites and a connected network provided by V-enriched diffusion pathways. Ti5.2V0.64Fe3.5Cu0.5Ce0.14 showed similar kinetics to Ti5.5V0.65Fe3.7Ce0.15， although its storage capacity slightly decreased to 1.98 wt.% because of the lower hydrogen affinity of Cu. When the hydrogenation temperature increased， Ti5.5V0.65Fe3.7Ce0.15 showed less degradation in reversible capacity， with a decrease of only 0.08 wt.% compared with 0.40 wt.% for Ti6Fe4 Furthermore， Ti5.2V0.64Fe3.5Cu0.5Ce0.14 exhibited a 0.10 wt.% increase in reversible capacity due to the additional strain release from Cu addition. In cycling tests， apart from the capacity loss caused by hydrogen trapped in TiV-containing hydrides， both multi-element substituted alloys showed less than 5% degradation after 50 cycles. Overall， these designed alloys demonstrate that composition tuning can effectively reduce activation difficulty， enhance storage capacity， and optimize the plateau pressure range while maintaining cycling stability for practical applications.
