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Abstract: A compact tubular sensor based on sodium super ionic conductor (NASICON) and Pr6O11-doped SnO2 sensing electrode was designed for the detection of H2S. In order to reduce the size of the sensor, a thick film of NASICON was formed on the outer surface of a small Al2O3 tube; furthermore, a thin layer of SnO2 with nanometer size was attached on the NASICON as a sensing electrode. Compared with pure SnO2, Pr6O11-doped SnO2 was found to be more suitable for the sensing electrode. The sensor using Pr6O11-doped SnO2 gave excellent sensing properties to 5–50ppm H2S in air at 200–400°C. The EMF value of the sensor was almost proportional to the logarithm of H2S concentration, the sensitivity (slope) was 74mV/decade at 300°C. It was also seen that the sensor showed a good selectivity to H2S against SO2, NO2, CH4 and CO, and an excellent resistance to water vapor. The sensor had speedy response kinetics to H2S, the 90% response time to 5, 20 and 50ppm H2S was 8, 6 and 4s, respectively, and the recovery time was 12, 18 and 30s, respectively. On the basis of XPS analysis for the H2S-adsorbed sensing electrode, a sensing mechanism involving the mixed potential at the sensing electrode was proposed. [Copyright &y& Elsevier]

Abstract: A new oscillatory phenomenon based on Fe3+/Fe2+ was investigated systematically at the water/1,2-dichloroethane (W/DCE) interface by cyclic voltammetric technique. We focus our attention on study the concentrations of Fe3+/Fe2+ influence on oscillatory phenomena appearance in this paper. It was found that the current oscillation only occurred in the site of oxidation peak of Fe2+, and was related to the concentration of Fe3+ in the aqueous phase, indicating that the oscillation is caused by the specific adsorption of ion pairs at the liquid–liquid interface between Fe3+ in the aqueous phase and TPB− in the organic phase. Furthermore, DFT theory was used to calculate the mechanism of ion pair formation for the first time. The result suggested that TPB−Fe3+TPB− ion pair has the lowest-energy state, which provided qualitative support for ion pair embodied state. Combining experiment results and theoretical calculation, a specific adsorption of ion pair model on liquid/liquid interface was proposed and a mechanism for the observed current oscillation is also discussed in this paper. In addition, a spectrophotometric experiment was performed to evidence a strong attractive interaction between Fe3+ and TPB−. [Copyright &y& Elsevier]