Metal-oxideNanoparticle- based COz gas sensor Via Spark Ablation
X. He (TU Delft - Mechanical Engineering)
S Vollebregt – Mentor (TU Delft - Electronic Components, Technology and Materials)
P. Taheri – Graduation committee member (TU Delft - Team Peyman Taheri)
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Abstract
Carbon dioxide (CO2) detection is vital in various fields, such as environmental monitoring, healthcare, and industry. Metal oxides are the sensing material because of their high sensitivity and stability. However, they have limitations in detecting CO2 as CO2 is a chemically stable gas, which can be mitigated by post-treatment such as annealing or doping noble metals. Spark ablation, a versatile technique for synthesizing nanoparticles with controlled size and composition, was utilized in this study to produce SnO2 nanoparticles, which were subsequently integrated into a specifically designed interdigitated electrode (IDE) structure for CO2 sensing. The IDE configuration featured a fixed finger width of 5 μm, with the gap width ranging from 2 to 15 μm, and devices were fabricated with SnO2 sensing areas of 1×1 cm and 1×4 cm. Noble metals such as Ag and Ru were decorated on the SnO2 layer to enhance the catalytic activity and promote the CO2 adsorption reaction. Surface densities of Ag and Ru under various printing conditions were analyzed using spark ablation. Based on these results, decorated SnO2 layers were fabricated with surface coverages of 19% Ag and 12% Ru, respectively. Annealing was performed later at 450°C and 600°C, and XRD results revealed that the grain size of SnO2 increased from 7 nm at 450°C to 12 nm at 600°C. Gas tests conducted in an N2 atmosphere demonstrated CO2 detection at 200°C, with a higher response observed for samples with Ru nanoparticle decoration, approximately twice that of the undecorated sample. However, no recovery was observed. Overall, samples annealed at 450°C exhibited higher responses compared to the ones annealed at 600°C. In an N2/O2 atmosphere, the sensor exhibited almost no response to CO2. Further investigation revealed a response to O2, suggesting that the low operating temperature may hinder the reaction between CO2 and adsorbed oxygen species, failing CO2 sensing. An anomalous p-conductive behaviour was also observed in response to O2. Experimental results showed no correlation between device area, gap width, and sensing performance.