Behaviors of hydrogen adsorption over TiO2-coated activated carbon under various electric potentials were studied. TiO2 particles were introduced onto carbon via the hydrolysis of TiCl4 in acid solution. The results showed that the hydrogen adsorption first increased and then decreased with the increase of electric field. The improved storage was due to a stronger interaction between charged carbon surface and polarized hydrogen molecule caused by field induced polarization of TiO2 coating. When the electric field was sufficient to cause considerable ionization of hydrogen, the decrease of hydrogen adsorption occurred. The electricity detected at 3000 V was a sign of ionization of hydrogen. The DFT calculations showed a much stronger binding between TiO2-doped coronene and hydrogen molecule under an electric field, which is consistent with our experimental observations. Copyright (C) 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.