ENHANCING PERFORMANCE OF BINARY METAL OXIDE-BASED ACTIVE MATERIALS BY THE ADDITION OF SILVER FOR ETHYLENE GAS DETECTION

• Main Author: Prayoga, Adyatma
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/84253
• Institution: Institut Teknologi Bandung

Various types of fruits and the ability to produce up to tens of millions of tons of fruit each year are the potentials that Indonesia has in the fruit industry sector. However, this potential also raises problems in this field, namely fruits that are damaged due to rot or overripe throughout the supply chain, which is called food loss. Rotten or overripe fruit can be caused by ethylene gas (C2H4), a hormone to stimulate the rate of fruit ripening. To overcome this problem, early detection of ethylene gas is needed. Metal oxide semiconductors have the potential as active materials for detecting ethylene gas, but metal oxide semiconductors still have weaknesses such as relatively low response, low selectivity, and high working temperatures. Efforts are needed to overcome these weaknesses. In this study, Fe2O3 was used which was added with silver as an active material to detect ethylene gas. The purpose of this study was to explain how different silver addition methods affect material properties and to explain the effect of different metal oxide-silver structures with silver on the performance of detecting ethylene gas. Two types of methods were used in adding silver, namely one-pot synthesis and chemical reduction method using NaBH4 as a reducing agent. The XRD results showed that Fe2O3-silver with one-pot synthesis had diffraction peaks from various variations of silver oxide (AgxOy). While Fe2O3-silver with the chemical reduction method had diffraction peaks from metallic silver. The XRD results prove that silver was successfully added to Fe2O3. This statement is also supported by the EDS results which show the presence of silver elements evenly distributed in the sample. The SEM results showed that there was a change in the morphology of the nanorods into an irregular shape in the sample added with silver with one-pot synthesis. The SEM results also showed agglomeration in samples with higher silver concentrations. While the sample added with silver with the chemical reduction method showed no significant morphological changes. The BET analysis results showed that there was a decrease in the specific surface area of the material variation with the addition of one-pot synthesis silver compared to the pure Fe2O3 material. While the specific surface area of the sample variation added with silver with the chemical reduction method increased compared to the pure Fe2O3 material. It was found that the specific surface area reached the optimum value at a concentration variation of 3%. The test results at 15 ppm of ethylene gas at a working temperature of 250ºC showed that the variation of samples added with silver using the chemical reduction method increased at silver concentrations of 3% and 5%. While the sample added with silver using the one-pot synthesis method produced a smaller response value compared to the response value of pure Fe2O3 material. The increase in response value from the variation of materials added with silver using the chemical reduction method was caused by the electrical sensitization and chemical sensitization mechanisms. Electrical sensitization occurs at the interface between silver and Fe2O3, where the formation of a Schottky Barrier thickens the depletion layer. This increase in the depletion layer is related to the greater initial resistance so that the response value can increase. In addition, the chemical sensitization process that increases the number of reactive oxygen ions on the Fe2O3 surface due to the spillover effect is also the reason behind the increase in response value. While the sample added with silver using the one-pot synthesis method experienced a decrease in response value due to the active Fe2O3 sites being covered by silver oxide. Samples added with silver using the chemical reduction method also have good selectivity towards ethylene compared to the interfering gas, namely carbon dioxide. Keywords: Gas Sensor, Ethylene, Silver, Metal Oxide, Fe2O3 ?