Efficient NH Detection Based on MOS Sensors Coupled with Catalytic Conversion.

A solution of NH detection based on catalytic conversion of NH into NO was proposed by using MOS gas detectors and Pt-supported catalysts. The catalysts convert NH into NO, which is a very sensitive analyte for MOS detectors. Catalysts based on Pt-loaded HZSM-5 and AlO were prepared by wet impregnation. MOS detectors were fabricated from nanosized InO and WO using screen-printing techniques. As expected, MOS sensors based on InO and WO have an extremely high sensitivity to NO; nevertheless, they have a relatively low response to NH and a large cross-sensitivity to typical interfering gases such as CO and ethanol. By the present solution, MOS sensors could very sensitively respond to NH, even down to 0.25 ppm. In addition, it was also found that the catalysis also combusts the reducing gases into CO and water and consequently significantly improves the selectivity of NH. Lastly, we would to like to stress that the proposed concept of the catalytic conversion method suggests the potential utility for broader measurements by using different catalysts and gas detectors and that only a part of the usage for NH was presented here.