Doped effects on the microstructure and electrochemical hydrogen storage performances of BiFeO3 with La, Ce, Nd, and Co ions

This study first used bismuth ferrite (BiFeO 3 ) as the negative electrode for Nickel-Metal hydride(Ni-MH) batteries and examined the effects of 2 at% doping of La, Ce, Nd, Co on its hydrogen storage. The XRD results showed that the obtained solid solutions remained the original rhombohedral R3c structure of BiFeO 3 , doping reduced the grain sizes and introduced lattice strains. Spectroscopic analyses showed that doping generated extra oxygen vacancies and defects, and red-shifted the band gap. Electrochemical evaluations revealed that the Co doped sample exhibited the most outstanding electrochemical hydrogen storage performance, its maximum discharge capacity achieved to 661.5 mAh g −1 and equivalent of hydrogen absorption content of 7.72 wt%, which was substantially higher than those of pure BiFeO 3 (289.5 mAh g −1 and 3.38 wt%). Kinetic analysis further confirmed a remarkable improvement in hydrogen mobility. Additionally, the hydrogen storage mechanism was elucidated based on sample structure and electrochemistry.