Synthesis and characterisation of gas sensor materials obtained from Pt/Zn/Al layered double hydroxides

We reported about the possibility to employ Zn(Al)O and Pt–Zn(Al)O mixed oxides obtained from layered double hydroxides (LDH) as gas sensor materials. We prepared the samples following two different routes: a classical co-precipitation and a sol–gel method. After structural and textural characterisation, the powders were studied by FT-IR spectroscopy under different controlled atmospheres at different temperatures. Eventually, conductance measurements were performed on thick films of these materials for testing their response to CO, CH4 and benzene. FT-IR spectra recorded after reducing treatments in the three different gases show an increase in the absorbance for all the samples studied. For the co-precipitated samples the absorption increases in intensity on decreasing the wavenumbers (free-carrier absorption). For the sol–gel samples the absorption shows a maximum (absorption due to trapped electrons). Concerning the conductance measurements, it was interesting to note that Pt markedly increases the electrical responses and that the presence of humidity affects significantly the responses towards CO and CH4, but not the responses towards benzene. Moreover, sol–gel samples show high stability of the performances on varying working temperature.