Room Temperature Amperometric Ammonia Sensor Based on Pt and Pt–Ir Porous Ceramic Electrodes

The amperometric ammonia sensors based on Pt (electroplating) and Pt–Ir (electroplating)/Pt(sputtering)/porous ceramic plate (Pt(E)/Pt(S)/PCP and Pt–Ir(E)/Pt(S)/PCP) electrodes have been fabricated to detect the concentration of ammonia in 1.0 M KOH aqueous solution. The morphologies, crystallinities, and compositions of the sensing electrodes were analyzed by scanning electron microscope, X-ray diffraction, and electron probe micro-analyzer, respectively. The analysis results indicated that both the deposited Pt and Pt–Ir layers exhibited amorphous type. The sensitivities of the amperometric ammonia sensor for
$0\sim 155.5$
ppm NH
₃
were obtained to be 8.31 ± 0.03 and
$7.86~\pm ~0.02~\mu \text{A}$
ppm
$^{-1}$
cm
$^{-2}$
, respectively, when the Pt(E)/Pt(S)/PCP and Pt–Ir(E)/Pt(S)/PCP were used as the sensor electrodes, respectively. While the Pt(E)/Pt(S)/CP and Pt-Ir(E)/Pt(S)/CP electrodes were reactivated at −0.8 V for detecting every level of NH
₃
, the sensitivities of the amperometric NH
₃
sensor would separately increase by 32.5 ± 0.12% and 26.9 ± 0.09%.