Nitul Kakati

Anode Catalysts for Direct Methanol Fuel Cells in Acidic Media: Do We Have Any Alternative for Pt or Pt-Ru?

Do We Have Any Alternative for Pt or Pt−Ru? Nitul Kakati,† Jatindranath Maiti,† Seok Hee Lee,† Seung Hyun Jee,† Balasubramanian Viswanathan,*,‡ and Young Soo Yoon*,† †Department of Chemical Engineering, Gachon University, 1342 Seongnamdaero, Sujeong-gu, Seongnam-si, Gyeonggi-do 461-701, Republic of Korea ‡National Centre for Catalysis Research, Department of Chemistry, Indian Institute of Technology Madras, Chennai, Tamil Nadu 600036, India

Sensitivity Enhancement of ZnO Nanorod Gas Sensors with Surface Modification by an InSb Thin Film

Zinc oxide (ZnO) nanorods were prepared on sol–gel ZnO seed-coated alumina substrates by a hydrothermal method. A very thin layer of indium antimonite (InSb) was deposited on the ZnO nanorods by a thermal evaporation technique. X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM) were applied to analyze the quality of the ZnO nanorods. XRD results showed that the as-synthesized ZnO nanorods were well crystallized in hexagonal wurzite ZnO. An X-ray photoelectron spectroscopy (XPS) study confirmed the deposition of InSb on the ZnO nanorods. The activation energies of sensors fabricated from ZnO nanorods and InSb-deposited ZnO nanorods were calculated. It was found that the activation energy of the InSb-deposited ZnO nanorods was very small. The sensitivity of the sensors towards acetone gas was measured at concentrations of 500–5,000 ppm and at operating temperatures ranging from 200 to 350 °C. The sensitivity of the InSb-deposited ZnO nanorod sensor was much higher than that of the ZnO nanorod sensor. The optimum temperature of the sensors was found to be 300 °C.

Hydrothermal Synthesis of Pt–Ru–W Anode Catalyst Supported on Multi-Walled Carbon Nanotubes for Methanol Oxidation Fuel Cell

PtRuW/multiwalled carbon nanotubes (MWCNTs) nanoparticles were synthesized using a hydrothermal method. To characterize the catalysts, X-ray diffraction (XRD), transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS) were carried out. The average diameter of the PtRuW nanoparticles supported on MWCNTs was 2.82 nm, and the particles were well dispersed. The catalytic activity of the PtRuW/MWCNTs was measured by cyclic voltammetry, chronoamperometry and impedance spectroscopy in a 0.5 M H2SO4 solution containing 1.0 M CH3OH and was compared with that of a PtRu/MWCNTs catalyst prepared by the same method. The results demonstrate that the catalytic activity and tolerance performance of the PtRuW/MWCNTs for methanol oxidation are higher than that of PtRu/MWCNTs due to the effect of tungsten oxide, which cleans the active reaction sites on the platinum.

Ohmic contact between ZnO and Pt by InSb layer in a ZnO Schottky diode

The surface of the ZnO thin films was modified by a thin InSb layer by using a thermal evaporator to increase the work function without altering the physical properties of the film. We expected that the InSb thin layer with a high work function could achieve the Ohmic contact between the ZnO and Pt electrodes by reducing an energy barrier due to increase in the ZnO thin film. The Ohmic contact was achieved in the interface between the ZnO and Pt electrodes by the InSb thin layer.

Work Function Effects of Nano Structured ZnO Thin Film on the Acetone Gas Sensitivity

We deposited various nano structured ZnO thin films with plasma treatment on an alumina substrate and fabricate ZnO sensors for acetone detection. The ZnO sensors with various nano structures and the plasma treatment were deposited by radio frequency (RF) magnetron sputtering method with RuO 2 micro heater and Ru electrode. In order to control a work function intentionally, the various deposition conditions and the plasma treatment were used. Sensitivities of the ZnO sensor were measured in acetone vapor and air at 250 degree C. In conclusion, we suggested that the sensitivity of ZnO sensors for acetone strongly depends on the work function of the as-deposited or plasma treated nano structured ZnO thin films.