Some experimental evidences for hydrogen spillover on Pt/Al2O3 catalysts by electrical conductivity transient response Original Research Article

Transient method and temperature-programmed desorption (TPD) measurements based on the response of the AC electrical conductance (G) have been used to characterise a H2–Pt/Al2O3 system. It was shown that if the surface was insufficiently cleaned and contained traces of oxygen, the transient response H2 (inc., 0) – G was of the overshoot type. Its characteristics are related with the involvement of some competitive processes controlled by the highly exothermic parasite reaction between hydrogen and oxygen. The “ignition” reaction O2–H2 produces the sharp increase of the amount of the spillover hydrogen, which decreases by back spillover and desorption as much as the“extinction” is in progress. The G-TPD profiles, registered after H2 (inc., 0) – G transient experiments and in conditions simulating the reaction sequence of the proposed mechanism, provide additional support for this statement.