Room-Temperature Hydrogen Uptake by TiO₂ Nanotubes

Abstract

TiO(2) nanotubes can reproducibly store up to approximately 2 wt % H(2) at room temperature and 6 MPa. However, only about 75% of this stored hydrogen can be released when the hydrogen pressure is lowered to ambient conditions, suggesting that both physisorption and chemisorption are responsible for the hydrogen uptake. FTIR spectroscopy, temperature-programmed desorption (TPD), and pressure-composition (P-C) isotherms suggest that 75% of the H(2) is physisorbed and can be reversibly released upon pressure reduction. Approximately 13% is weakly chemisorbed and can be released at 70 degrees C as H(2), and approximately 12% is bonded to oxide ions and released only at temperatures above 120 degrees C as H(2)O.