Catalytic effect of Gd2O3 and Nd2O3 on hydrogen desorption behavior of NaAlH4

This study investigated the effect of Nd2O3 and Gd2O3 as catalyst on hydrogen desorption behavior of NaAlH4. Pressure-content-temperature (PCT) equipment measurement proved that both two oxides enhanced the dehydrogenation kinetics distinctly and increasing Nd2O3 and Gd2O3 from 0.5 mol% to 5 mol% caused a similar effect trend that the dehydrogenation amount and average dehydrogenation rate increased firstly and then decreased under the same conditions. 1 mol% Gd2O3–NaAlH4 presented the largest hydrogen desorption amount of 5.94 wt% while 1 mol% Nd2O3–NaAlH4 exerted the fastest dehydrogenation rate. Scanning Electron microscopy (SEM) analysis revealed that Gd2O3–NaAlH4 samples displayed uniform surface morphology that was bulky, uneven and flocculent. The difference of Nd2O3–NaAlH4 was that with the increasing of Nd2O3 content, the particles turned more and more big. Compared to dehydrogenation behavior, this phenomenon demonstrated that small particles structure were beneficial to hydrogen desorption. Besides, the further study found that different catalysts and addition amounts had different effects on the microstructure of NaAlH4.

► Ga2O3 and Nd2O3 as catalysts enhanced the dehydrogenation kinetics of NaAlH4 visibly.
► Both two oxides caused a similar effect trend on dehydrogenation amount and rate.
► SEM analysis of Gd2O3 shows uniform surface morphology after ball milling.
► The microstructure of Nd2O3 particles turn bigger and bigger with amount increase.
► SEM analysis proves small particles structure is beneficial to hydrogen desorption.