Effects of the hierarchical pyrolysis polyaniline on reversible hydrogen storage of LiBH4

In this work, LiBH 4 –20 wt% PP composite was prepared by ball-milling with as-synthesized hierarchical pyrolysis polyaniline (PP) and LiBH 4 , and the hydrogen sorption performance as well as catalytic mechanism of the composite was studied. It is found that the onset desorption temperature of the composite decreases to 75 °C, almost 235 °C lower than that of the milled LiBH 4 . Moreover, the composite could release 4.1 wt% H 2 and rehydrogenate a total of 4.4 wt% H 2 when the temperature raiseds up to 400 °C, showing an outstanding reversibility, which even 3.9 wt% H 2 can be kept after five cycles. Through scanning electron microscopy (SEM) observation and X-ray diffraction (XRD) analysis, we found that the PP surface forms some nanoholes after hydrogenation-dehydrogenation cycles, which leads to the confinement of some LiBH 4 in the PP nanoporous structure, therefore, the hydrogen sorption kinetics and reversibility are significantly enhanced. In addition, we also found the oxygenic groups of the PP can react with LiBH 4 forming LiBO 2 and Li 3 BO 3 , where the containing Li–B–O bonds loaded in the porous structure of the PP catalyze the hydrogenation reaction of LiBH 4 .