Synthesis of PuNi3-type PrCo3 and its hydrogen absorption–desorption property

• The reversible hydrogen capacity of PrCo3 reached 0.95 H/M.
• The structure of PrCo3H3.8 is described by space group R32.
• Crystal lattice of PrCo3H3.8 expands anisotropically with increasing hydrogen.

We synthesized the intermetallic compound PrCo3 with the PuNi3-type structure. The structural parameters were refined by the Rietveld method. The refined lattice parameters were a = 0.5076(1) nm and c = 2.4831(6) nm. The pressure-composition (PC) isotherm of PrCo3 was measured at 413 K. The maximum hydrogen capacity reached 0.95 H/M. Two plateaus were observed in the absorption–desorption process. The hydrogenation properties were reversible. The structure change of the hydride phase was investigated by X-ray diffraction. The space group of the full hydride phase (PrCo3H3.8) was determined to be R32; the metal sublattice of the original alloy (space group R-3m) transformed to R32 during the hydrogen absorption process. The volume expansions of the unit cell, and the CaCu5-type and MgZn2-type cells of the full hydride phase from the original alloy were 25.0%, 18.4%, and 22.7%, respectively. The structural change was accompanied by anisotropic lattice expansion.