A composite based on Fe substituted TiVNi alloy: Synthesis, structure and electrochemical hydrogen storage property

The TiV(1−x)NiFex (x = 0, 0.1, 0.2, 0.3 and 0.4) alloy ribbons are synthesized by arc-melting and subsequent melt-spinning techniques. The structure of the alloys is characterized by XRD. The electrochemical properties including the maximum discharge capacity, cyclic stability and the high rate dischargeability, etc. are tested. The results show that the structure of all TiVNi alloy mainly consists of the icosahedral quasicrystal (I-phase), Ti2Ni-type face centered cubic (FCC) phase and body centered cubic (BCC) solid solution phase. After adding some amount of Fe to TiVNi alloys, for TiV0.9NiFe0.1 (x = 0.1) alloy, the XRD pattern is characterized by the FCC and the BCC phase, while the structure of TiV1−xNiFex alloys (x = 0.2, 0.3 and 0.4) consists of the BCC solid solution phase alloy. The maximum discharge capacity of the alloy electrodes increases firstly and then decreases with increasing x, the same as the high-rate dischargeability. The optimal value of C240/C30 is 84.2%, corresponding to x being 0.2 and the discharge current density is 240 mA/g. In addition, the electrochemical reaction kinetics of the alloy electrodes is also studied by electrochemical impedance spectroscopy and hydrogen diffusion coefficient (D). ► The structure of the I-phase, FCC and BCC of the TiVNi transforms to BCC phase. ► Appropriate Fe addition is effective in improving the activation performance. ► The thickness of the oxide layer increases with increasing Fe content.