Microstructure and electrochemical hydrogen storage properties of nanosized doped La2Ti2O7 solid solutions

Abstract

Hydrothermal-sintering method was employed to obtain pure and Li, Co, Mn, Cu and Zn doped La₂Ti₂O₇ solid solutions. The substitution sites of doping ions are discussed. X-ray diffraction (XRD) results indicate that the doped ions were incorporated into the lattice of La₂Ti₂O₇ successfully. Transmission electron microscopy (TEM) measurements prove that the doped ions with smaller radius induce the contraction of lattice. The results of UV and photoluminescence (PL) tests show that the doped ions cause the red-shift of band gap energies and enhance the concentrations of oxygen vacancies and defects. The electrochemical hydrogen storage properties of the samples were measured at 303 and 333 K, respectively. The discharge capacities of the doped samples keep growing by increasing the cycle number at 333 K. Meanwhile, the doped samples possess better kinetic performances than the pure La₂Ti₂O₇. Among the samples, the Mn, Co and Li ions doped samples exhibit better electrochemical hydrogen storage properties. The hydrogen storage properties are closely related with the characteristics of doped ions, crystallite sizes, the content of the oxygen vacancies and defects in the lattice of La₂Ti₂O₇.