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- Phase pure PbS and lanthanum doped PbS thin films have been deposited by the spray pyrolysis technique. All the deposited films were gray to black, pin hole free and strongly adherent to the ITO glass substrates. The substrate temperature was varied between 450 and 500 °C, with doping concentration ratios of 1, 5 and 10% for La. The doping performed at 450 °C, showed phase segregation whereas successful incorporation of La in the PbS lattice was achieved at 500 °C. The films were characterized by x-ray diffraction (p-XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), Energy-dispersive X-ray spectroscopy (EDX), and ultraviolet visible spectroscopy (UV). The sensitivity of the as deposited thin films was also tested against hydrogen gas. The sensor material was exposed to a low concentration of 200 ppm of the target gas to determine the sensitivity performance of the sensor, at different temperatures while measuring the variation in the resistance. The doping of lanthanum significantly enhances the sensitivity of the PbS thin films against the target gas. The gas sensor exhibited n-type conductivity as confirmed by the decrease in resistance on exposure to hydrogen. The as prepared catalysts show good sensing behavior near room temperature and at low concentration of hydrogen at 200 ppm without the need to apply an external voltage.
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- The present work reports the study of hydrothermally synthesized Ni/NiCo2O4 with different ratios of nickel (10, 20 and 30) %. The crystallite size was decreased from pure nickel cobaltite (NiCo2O4) to the 10, 20 and 30% Ni/NiCo2O4 samples. In a basic media by utilizing the chrono-amperometry method, the electro-chemical behavior and persistence on glassy carbon adjusted electrode was followed across methanol electro-oxidation. It is clearly seen with growing the methanol concentration up to to 2 M, a clear increase of the current density was obtained for the pure nickel cobaltite catalyst which may be related to the increased oxidation at the surface. Scanning electron microscopy (SEM) images of the pure catalyst shows needle-like structures without agglomeration, recording a highly current density of 80 mA/cm2 at 2 M of methanol and scan rate of 60 mV/s. All the tested electrodes show a higher stability hence, the current decayed more slowly with less corrosion impact. Surface modification, barrier and block action effect by Ni on the surface of the catalyst, nearly 80% shortage in the efficiency was observed by using 10 % of Ni. By increasing the ratio to 20 and 30 % the efficiency dropped sharply. Hence, the following order of reactivity was observed: pure nickel cobaltite > 10% Ni-nickel cobaltite > 20% nickel cobaltite> 30% nickel cobaltite, according to their current density values.
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