H2S sensing characteristics of Ni-doped CaCu3Ti4O12 films synthesized by a sol-gel method

Abstract The problem of detecting the toxic hydrogen sulfide (H 2 S) gas at part per million levels in air by means of simple solid state gas sensors is relevant to environmental and gas processing industries. In this work, high-performance H 2 S gas sensors are developed based on nickel-doped calcium copper titanate (Ni-doped CCTO) thin films synthesized by a sol-gel method. From gas-sensing measurements, the response of Ni-doped CCTO sensing films increased substantially with increasing Ni doping level from 1.5 to 7.3 wt%, revealing a catalytic effect of Ni on the surface reactions with adsorbed H 2 S molecules. In particular, 7.3 wt% Ni-doped CCTO sensors offered a high response of 120 for 10 ppm of H 2 S at the optimal operating temperature of 250 °C, an order of magnitude higher than that of undoped one. In addition, the response time dropped significantly from ∼80 s to ∼4 s while the recovery time slightly improved as the Ni doping content increased from 0 to 7.3 wt%. Moreover, the Ni-doped CCTO sensors exhibited good reproducibility and high H 2 S selectivity against ethanol, H 2 , NO 2 and NH 3 . Therefore, the Ni-doped CCTO sensors are highly promising for sensitive and selective detections of H 2 S.