Ammonia sensing characteristics of La10Si5MgO26-based amperometric-type sensor attached with nano-structured CoWO4 sensing electrode

• An amperometric sensor based on solid electrolyte is developed for NH3 determination.
• La10Si5MgO26 is used as electrolyte for the amperometric NH3 sensor.
• Nano-structured CoWO4 sensing electrode is fabricated by impregnation method.
• Good response/recovery, reproducibility and selectivity of the sensor are achieved.

An amperometric type NH3 sensor based on La10Si5MgO26 electrolyte is reported in this paper. The design of this type sensor is significantly simplified due to the in-situ preparation of the nano-structured CoWO4 sensing electrode in the pre-sintered porous La10Si5MgO26 layer by impregnation method. The XRD and SEM investigations show that the CoWO4 particles with the diameters about 50–100 nm are obtained after calcined at 800 °C for 3 h. The performance of the sensor is investigated with respect to the sensitivity at different temperatures, influence of the CoWO4 loading and calcination temperatures, reproducibility and selectivity. The complex-impedance measurements are performed to analyze the mechanism of the sensor. The results show that the sensor exhibits good amperometric response-recovery characteristics to NH3 in the temperature range of 500–650 °C at a constant bias voltage of 400 mV. Good linear correlations between the response currents and the NH3 concentrations for 30–300 ppm are obtained. The influences of the loading and calcination temperature of the CoWO4 sensing electrode on the sensing performance of the sensor suggest that the enhanced triple phase boundary is in favor of the improvement of the sensing performances. The present sensor also displays good reproducibility and low cross-sensitivities to various co-existing gases.

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