Hydrogen Oxidation-Mediated Current Discharge in Mesoporous Pt/TiO 2 Nanocomposite.

Here we report on direct evidence of a correlation between hydrogen-to-water oxidation on mesoporous Pt/TiO ₂ nanocomposites at room temperature and the conversion of surface-released chemical energy into a stationary electrical current. The Pt phase of this heterojunction device is an electrically continuous 15 nm thick mesh deposited onto a mesoporous TiO ₂ substrate fabricated with a plasma electrolytic oxidation process. The H ₂ O turnover frequency approaches an asymptotic value associated with the saturation of the Pt/TiO ₂ interface as the concentration of hydrogen gas is increased. In situ measurements of the reaction-induced current concurrently with mass spectrometry measurements illuminate the polarity switch of the reaction current (from thermionic emission to a reverse steady-state flow) simultaneously with the production of water. Furthermore, a concentration-dependent value of 5 min is measured as the time constant for the adsorption of the initial addition of H ₂ and H ₂ O formation and desorption.