Effects of Mo and Ti on monohydride stability and hydrogen storage capacity in BCC Nb–Mo–Ti alloys

This study investigates the relationship between the monohydride and reversible hydrogen capacity of Nb–Mo and Nb–Mo–Ti alloys with a body-centered cubic (BCC) structure. Increasing the Mo content in the Nb–Mo alloys increases the plateau pressure and decreases the hydrogen content of monohydrides in the alloys. The increase in plateau pressure prevents sufficient hydrogen absorption over the hydrogen pressure range of the study (up to 9.8 MPa) at 40 °C. The plateau pressure decreased after adding Ti as a third element. Although adding Mo and Ti to Nb scarcely changes the maximum hydrogen capacities, it decreases the hydrogen content and the thermal stability of monohydrides. Accordingly, the reversible hydrogen capacities increase with increasing Mo and Ti contents in Nb–Mo–Ti alloys. At 40 °C, the maximum hydrogen capacity and reversible hydrogen capacity are 1.82 H/M and 1.08 H/M, respectively, in the Nb–25Mo–30Ti alloy. • Adding Mo to Nb reduced the hydrogen content and volume expansion between the alloys and monohydrides. • A hydrogen-absorbing BCC structure was obtained by adding Mo and Ti to Nb. • Adding Mo and Ti to Nb reduced hydrogen content and monohydride stability, while keeping maximun capacity nearly unchanged. •The reversible hydrogen capacity was maximized at 1.08 H/M at 40 °C in the Nb–25Mo–30Ti alloy.