Evolution of the active species and catalytic mechanism of Ti doped NaAlH4 for hydrogen storage

Abstract The catalytic mechanism of Ti doped NaAlH 4 for hydrogen storage remains unconfirmed. Here, we investigated the evolution of active species in Ti doped NaAlH 4 system by XRD, XPS and TEM. The results reveal that the evolution of the Ti addition in doped NaAlH 4 is Ti 3+  → amorphous Ti 0  → Al Ti species → Al 3 Ti intermetallic. TEM results show that the average particle size of the Al Ti species and Al 3 Ti intermetallic is about 30 nm, and Ti element is uniformly distributed in Al matrix. In further, we discussed the catalytic mechanism and role of active species in Ti doped NaAlH 4 system according to experimental and theoretical calculation. The rehydrogenation process of Ti doped NaAlH 4 system can be divided into three steps: (1) H 2 dissociation, (2) H atom spillover and alanes (Al x H y ) formation and (3) complex hydrides formation. The addition of Ti can catalyze the process of H 2 dissociation, H atom spillover and formation of alanes. More importantly, the current work may provide a general approach to investigate the catalytic mechanism of other doped complex hydrides for hydrogen storage system.