Lateral hydrogen diffusion

As the working temperature of the substrate was increased, the induction period (the delay time) of increased conductivity decreased due to increased rate of lateral diffusion of hydrogen atoms towards the sensor. The activation energy for surface migration of particles along a Si02 substrate estimated from the tilt of the Arrhenius plot was found to be about 20 kj/mol. 

By varying the temperature at which the experiments were conducted and the distance between the activator and the sensor, the data were obtained (Fig. 4.17) which allowed us to calculate the activation energy of migration of hydrogen adatoms (protium and deuterium) along the carrier surface and coefficients of lateral diffusion of hydrogen atoms appearing due to the spillover effect (see Table 4.2). 

Zhang and Seitz somewhat later described a sensor for carbon dioxide that is based on measurement of fluorescence60. It was prepared by covering a pH sensor based on fluorescence with a C02-permeable membrane and contacting the pH-sensitive membrane with a reservoir of hydrogen carbonate. As CO2 diffuses across the membrane it causes a change in pH which is measured via the change in fluorescence from the base form of the... 

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