Resistivity of SnO2 Gas Sensor to Humidity, CO2 Gas, and Temperature in Food Decomposition Process

Abstract

This study aims to determine the sensitivity of a gas sensor based on a Cu substrate coated with SnO2 through an electroplating process, involving variations in electrolyte solution temperature and thermal oxidation. The deposition parameters were set as follows: electrolyte solution prepared by dissolving SnCl2 in distilled water, applied voltage of 4.5 V, electrode distance of 3 cm, and electroplating duration of 3 minutes. Sensor sensitivity tests were carried out by observing the food decomposition process, placing both the food sample and sensor in a testing chamber. Data acquisition of temperature, humidity, CO2 concentration, and sensor resistance was conducted using transducers and Logger Pro software. Based on the results, the sensor sample with an electrolyte temperature of 60°C (sample B) exhibited better performance than the sensor sample with an electrolyte temperature of 30°C (sample A). Sample B demonstrated greater responsiveness to temperature changes, with a coefficient of determination R2 = 0.66943. It also showed better detection of CO2 concentration changes with R2 = 0.98225. This improvement is attributed to a more effective electroplating process, as indicated by the mass change and thickness of the SnO2 layer. The sensitivity of sample B, defined by the equation S([CO2]) = 9.42E-5 - 1.17E-9[CO2], was superior to that of sample A, which followed the equation S([CO2]) = -2.34E-4 + 4.25E-9[CO2], as shown in the plotted graphs. Sample B exhibited a negative linear curve with a gentle slope, indicating a stable gas sensor behaviour.