Different effect between KH and KOH additives on the hydrogen storage properties of MgH2 doped with graphene

Abstract

The effect of KH on the hydrogen storage properties of MgH2 doped with graphene is investigated in this study, and compared with that of KOH. The results showed that MgH2 doped with 1 wt% KH and 1 wt% graphene has a significantly improved hydrogen storage performance. It desorbed 6.0 wt% H2 within 30 min at 300 °C, which is much faster than that of MgH2. However, its desorption rate is slower and its desorption activation energy is larger than those of the sample doped with KOH and graphene. The results showed the catalyst KMgH3 can be formed by the addition of either KH or KOH, so the different effect between KH and KOH might be due to the H-H exchange between KH and MgH2 which can suppress the desorption of MgH2, while the in-situ formed MgO by the addition of KOH can promote the desorption of MgH2.