Effects of Surface Area on All-Solid-Stated pH Sensor Based on Antimony Electrode

To realize the on-line and in situ pH detection in soilless culture, a new all-solid-stated pH sensor was presented. The pH sensor consisted of alumina ceramic (Al₂O₃) substrate, Sb/Sb₂ O₃ working electrode, Ag/AgCl reference electrode, Ag lead and pad. Sb thin film and Ag thin film were obtained by magnetron sputtering method, and then thermal annealing and Nafion modification was conducted to improve the performance of the sensor. Moreover, the influence of surface area of Sb electrode on the performance of pH sensor was investigated with the area of 4 mm², 9 mm², 16 mm2, 25 mm² and 36 mm², respectively. Through surface morphology analysis, energy spectrum analysis and electrochemical experiments, the pH sensor, which Sb electrode surface area is 16 mm², shows excellent comprehensive performance, with high sensitivity (67.3 mV/pH), short response time (less than 3.5 s), good stability (standard deviation less than 2 mV in 700 s period), low hysteresis (less than 1.63 mV) and low drift rate (less than 1.62 mV/h). The developed sensor can be applied in pH detection in soilless culture and is promising to popularize in industrial production.