LPG and NH3 sensing characteristics of DC electrochemically deposited Co3O4 films

Abstract

Present communication reports the LPG and NH 3 sensing properties of Co 3 O 4 films prepared on throughly cleaned stainless steel (SS) and copper ( CU ) substrates by using DC electrochemical deposition method followed by air annealing at 350°C/2 h. The resultant films are characterized by using X-ray diffraction (XRD), Raman spectroscopy and scanning electron microscopy (SEM). The LPG and NH 3 gas sensing properties of these films are measured at room temperature (RT) by using static gas sensing system at different concentrations of test gas ranging from ~ 25 ppm to 350 ppm. The XRD and Raman spectroscopy studies clearly indicated the formation of pure cubic spinel Co 3 O 4 in all films. The LPG and NH 3 gas sensing properties of films showed (i) the increase in sensitivity factor (S.F.) with gas concentrations and (ii) more sensibility to LPG as compared to NH 3 gas. In case of NH 3 gas (conc. ~ 150 ppm) and LPG gas (conc. ~ 60 ppm) sensing, the maximum S.F. = 270 and 258 are found for the films deposited on CU substrates, respectively. For all films, the response time (3–5 min.) is found to be much higher than the recovery time (30–50 sec). For all films, the response and recovery time are found to be higher for LPG as compared to NH 3 gas. Further, repeatability–reproducibility in gas sensing properties is clearly noted by analysis of data for number of cycles recorded for all films from different set of depositions.