Hydrogen sulfide sensing properties of NiFe2O4 nanopowder doped with noble metals

The paper reports the preparation and gas sensing characteristic of NiFe 2 O 4 nanopowder with and without different noble metal dopants such as Au, Pt, Pd. Ultrafine NiFe 2 O 4 powders were prepared by solid-state reaction of inorganic reagents, Ni(Ac) 2 , Fe(NO 3 ) 3 , and NaOH. XRD and Raman spectrometer were used to confirm the material structure and TEM to depict the crystallite microstructure. Au, Pd and Pt with different concentration were incorporated into NiFe 2 O 4 by impregnation technique. The electrical resistance response to H 2 S gas of the sensors based on the materials was investigated at different operating temperature and different gas concentrations. The results show that NiFe 2 O 4 is a p-type semiconductor and the sensor response of the doped NiFe 2 O 4 sensors was superior to that of the undoped ones. The sensor response increased linearly with the H 2 S gas concentration up to 100 ppm. The sensor with the 1.5 wt.% Au doped NiFe 2 O 4 showed excellent electrical resistance response towards 5 ppm H 2 S gas and the sensor response was up to 35.8 at 300 °C. The 1.5 wt.% Pt doped one was less sensitive to H 2 S but work at lower temperature, 240 °C. The gas-sensing behavior of these materials with respect to various reducing gases like liquefied petroleum gas (LPG), methane (CH 4 ), carbon monoxide (CO), butane (C 4 H 10 ) and hydrogen gas (H 2 ) suggested that the H 2 S gas sensor developed possesses an excellent selectivity. The interaction mechanism and correlations between the electrical resistance response and noble metal dopants were discussed.