We report on two distinct modes of catalytic oxidation of hydrogen to water on a mesoporous Pt/TiO2 structure with an electrically continuous 15 nm mesh-like Pt layer. The structure supported a continuous oxidation of hydrogen to water, starting at room temperature in 160 Torr O2 and also performed as a chemical–electrical transducer. Along with the usual fast reaction over the nanodispersed Pt, a 1200 times slower mode of the reaction is revealed by studying the reaction-induced currents. This slow mode leads to a surprisingly strong stationary current at electron yield 0.04, electromotive force −0.32 V, and short-circuit current density 12 μA/cm2 at room temperature. This phenomenon is explained by involvement of both Pt and TiO2 phases in the slow reaction flow, where a proton spillover mechanism of the observed electromotive force is suggested. The overall reaction current kinetics contains many autonomously formed features including peaks and alterations of the charge flow direction to manifest competition between various surface reaction regimes. These studies provide interesting opportunities for smart chemical sensors, transducers, and novel analytical tools.

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We report on the effect of temperature on the electric current induced in the mesoporous Pt/TiO2 structure by the room temperature surface chemical reaction of hydrogen and oxygen,13,14 which helps to unveil the physical origin of this current and the related electromotive force (chemi-EMF). We found that the temperature dependence of this reaction current has a clear multipeak structure, suggesting that at least two distinct processes contribute to the current generation. We suggest that the output current represents the interplay of both chemical and electrical processes, evidenced by the metastability of the room temperature reaction and by matching one of the current peaks with a water desorption peak for TiO2.

Reaction induced currents in planar metal/semiconductor nanostructures can provide a direct insight into underlying charge transfer processes involved in chemical energy dissipation at solid surfaces. This letter provides clear evidence of the nonthermal nature of chemicurrent induced by H 2 adsorption on a Pt/SiC nanostructure at room temperature in 760 Torr N 2 /O 2 mixtures with various oxygen fractions. The thermal effect of the reaction is reproduced also with admission of N 2 molecules to the sample. Only the process with H 2 leads to a detectable chemicurrent proving participation of nonthermal electrons in the charge transfer induced by hydrogen evolution on the nanostructure surface.

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