In the present work we have investigated the hydrogen sensing behavior of porous nanocrystalline zinc ferrite sensing elements. The response and recovery transients of conductance were modeled using Langmuir adsorption kinetics with two active adsorption sites in the sensing elements. Analyses of these transients revealed that the hydrogen gas adsorption and water molecule desorption are the two rate limiting processes controlling the response and recovery kinetics of gas sensing. Between the two adsorption sites, one of them with faster response as well as recovery time constants is argued to be the macroporous region of the sensing elements. On the other hand the mesoporous regions of the sensing elements are linked to comparatively slower response and recovery time constants. For these two sites the values of the activation energies for response and recovery behavior, estimated from the temperature dependence of respective time constants, were found to be different. The difference in respective activation energies for response as well as recovery is thought to be due to different chemiadsorbed oxygen species in these two sites.

MOF-coated NHA plasmonic gas sensor with high sensitivity and temperature-induced analyte discrimination.

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