Superior hydrogen storage and electrochemical properties of Mg–La–Pd trilayer films at room temperature

Abstract

A series of Mg–La–Pd trilayer films (La = 0.5–9 nm) have been prepared by magnetron sputtering method. When the thickness of La layer is larger than 3 nm, the distribution of La element becomes homogeneous. The hydrogen storage properties of the films under 0.1 MPa H2 and at 298 K are investigated by measuring their resistance and optical transmittance during the hydrogenation. The hydrogenation of the La 3 nm film saturates within 14 s and possesses the fastest absorption kinetics compared with other Mg–La–Pd films. The further increase of La thickness decreases the hydrogenation rate due to the decreased hydrogen diffusion rate through this layer. The La 3 nm film also exhibits the fast hydrogen desorption rate in air at room temperature. It releases 80% of hydrogen within 60 min. The electrochemical properties of the Mg–La–Pd films have been carried out in 6 M KOH with a three-electrode cell. Among these films, the La 3 nm film possesses the largest anodic area and anodic peak current, as well as the highest maximum discharge capacity of 377.8 mAh g−1.