A GaN-based Schottky diode synthesized with a hybrid surface structure is used to fabricate a new roomerature (25 °C) hydrogen and ammonia gas sensor. This hybrid surface structure includes platinum (Pt) nanoparticle (NP)/SiO2 nanosphere (NS) mixtures and a Pt thin film. The employed hybrid surface structure can effectively increase the catalytic reactivity of the Pt metal and enhance the related gas-sensing characteristics. In the experiment, a higher sensing response of 7.3× 105 (2.1× 10-1)is obtained under 1% H2/air (1000 ppm NH3/air) gas at 25 °C. Moreover, extremely low detecting levels of 100 ppb H2/air and 100 ppb NH3/air are acquired at 25 °C. The related hydrogen-and ammonia-sensing mechanisms are elucidated in this work. For wireless transmission and Internet of Things (IoT) application, the Kalman filter and shape-preserving piecewise cubic interpolation (SPPCI) algorithms are employed to substantially reduce redundant data and restore original results. More than 86.7% (97%) of the original data points are removed with a small mean recovery error (MRE) of 3% (0.3%) under 1% H2/air (1000 ppm NH3/air) gas at 25 °C.
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