Ti-Cr-Mn-Fe-based alloys optimized by orthogonal experiment for 85 MPa hydrogen compression materials

Abstract The development of hydrogen storage alloys possessing high plateau pressures for three-stage metal hydride hydrogen compressors (MHHCs), is critically significant for the safe and high-efficiency re-/charging of H2 in hydrogen refueling stations (HRSs). Herein, Ti-Cr-Mn-Fe-based alloys (Ti1.04+xCr2−y-zMnyFez, x = 0.02, 0.04, 0.06, y = 0.2, 0.3, 0.4, z = 0.5, 0.6, 0.7) synthesized by vacuum arc melting, with the single structure of C14 Laves and uniform element distribution, enable the final-stage compression units up to 85 MPa for MHHCs. It is demonstrated that both unit cell volume and maximum hydrogen capacity ( C max ) increase by the rising amount of Ti or decreasing Mn and Fe in the Ti-Cr-Mn-Fe-based alloys, whereas the dissociation pressures and plateau hysteresis ( H f ) at 223 K are reduced correspondingly, according to the orthogonal results. Meanwhile, as the over-stoichiometric amount of Ti increases, so does the plateau slope ( S f ) of the Ti-Cr-Mn-Fe-based alloys. Under the optimized conditions conducted by the orthogonal results, Ti1.08Cr1.3Mn0.2Fe0.5 exhibits comprehensively considerable hydrogen absorption/desorption properties, rendering it possible to be one of the most promising final-stage compression materials. Notably, the dehydrogenation enthalpy and entropy for Ti1.08Cr1.3Mn0.2Fe0.5 is determined to be 22.3 ± 0.3 kJ/mol and 117.8 ± 1.0 J/(mol K), respectively, with a corresponding hydrogen absorption pressure of 14.00 ± 0.52 MPa at 298 K and a dehydriding pressure of 89.19 ± 3.21 MPa at 363 K. Furthermore, the values of C max , H f , and S f are evaluated as 1.83 ± 0.01 wt%, 0.33 ± 0.01, and 0.72 ± 0.03, respectively, at 223 K.