Hydrogenation of palladium rich compounds of aluminium, gallium and indium

Palladium rich intermetallic compounds of aluminium, gallium and indium have been studied before and after hydrogenation by powder X-ray diffraction and during hydrogenation by in situ thermal analysis (DSC) at hydrogen gas pressures up to 39 MPa and temperatures up to 700 K. Very weak DSC signals and small unit cell increases of below 1% for AlPd 2, AlPd 3, GaPd 2, Ga 5Pd 13, In 3Pd 5, and InPd 2 suggest negligible hydrogen uptake. In contrast, for both tetragonal modifications of InPd 3 (ZrAl 3 and TiAl 3 type), heating to 523 K at 2 MPa hydrogen pressure leads to a rearrangement of the intermetallic structure to a cubic AuCu 3 type with an increase in unit cell volume per formula unit by 3.6–3.9%. Gravimetric analysis suggests a composition InPd 3H ≈0.8 for the hydrogenation product. Very similar behaviour is found for the deuteration of InPd 3. In situ differential scanning calorimetry of the hydrogenation of tetragonal InPd 3 (ZrAl 3 type) at 1.3 MPa hydrogen pressure.