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Adsorbed Oxygen Ions and Oxygen Vacancies; Their Concentration and Distribution in Metal Oxide Chemical Sensors and Influencing Role in Sensitivity and Sensing Mechanism
Ciftyurek, E.; Li, Z.; Schierbaum, K. Adsorbed Oxygen Ions and Oxygen Vacancies: Their Concentration and Distribution in Metal Oxide Chemical Sensors and Influencing Role in Sensitivity and Sensing Mechanisms. Sensors2023, 23, 29.
Ciftyurek, E.; Li, Z.; Schierbaum, K. Adsorbed Oxygen Ions and Oxygen Vacancies: Their Concentration and Distribution in Metal Oxide Chemical Sensors and Influencing Role in Sensitivity and Sensing Mechanisms. Sensors 2023, 23, 29.
Ciftyurek, E.; Li, Z.; Schierbaum, K. Adsorbed Oxygen Ions and Oxygen Vacancies: Their Concentration and Distribution in Metal Oxide Chemical Sensors and Influencing Role in Sensitivity and Sensing Mechanisms. Sensors2023, 23, 29.
Ciftyurek, E.; Li, Z.; Schierbaum, K. Adsorbed Oxygen Ions and Oxygen Vacancies: Their Concentration and Distribution in Metal Oxide Chemical Sensors and Influencing Role in Sensitivity and Sensing Mechanisms. Sensors 2023, 23, 29.
Abstract
Oxidation reactions on semiconducting metal oxides (SMOs) surfaces have been extensively worked on in catalysis, fuel cells, and sensors. SMOs engaged powerfully in energy-related applications such as batteries, supercapacitors, solid oxide fuel cells (SOFCs), and chemical gas sensors. The deep understanding of SMO surface and oxygen interactions and defect engineering has become significant because all those mentioned applications are based on the adsorption/absorption and consumption/transportation of adsorbed (physisorbed-chemisorbed) oxygen.
More understanding of adsorbed oxygen and oxygen vacancies (〖V_O^•,V〗_O^(••)) is needed, as the former is the vital requirement for sensing chemical reactions, while the latter facilitates the replenishment of adsorbed oxygen ions on the surface. We determined the relation between sensor response (sensitivity) and the amounts of adsorbed oxygen ions (O_(2(ads))^-,O_((ads),)^- O_2(ads)^(2-),O_((ads))^(2-)), water/hydroxide groups (H2O/OH^-), oxygen vacancies (〖V_O^•,V〗_O^(••)), and ordinary lattice oxygen ions (O_lattice^(2-)) as a function of temperature. During hydrogen (H2) testing, the different oxidation states (W6+, W5+, and W4+) of WO3 were quantified and correlated with oxygen vacancy formation (〖V_O^•,V〗_O^(••)). We used a combined application of XPS, UPS, XPEEM-LEEM, and chemical, electrical and sensory analysis for H2 sensing. We established a correlation between the H2 sensing mechanism of WO3, sensor signal magnitude, the amount of adsorbed oxygen ions, and sensor testing temperature.
This paper also provides a review of the detection, quantification, and identification of different adsorbed oxygen species. The different surface and bulk-sensitive characterization techniques relevant to analyzing the SMOs-based sensor are tabulated, providing the sensor designer with the chemical, physical, and electronic information extracted from each technique.
Keywords
Gas Sensor, Adsorbed Oxygen, Tungsten oxide, XPS, UPS, XPEEM, Sensing Mechanism, H2, Metal Oxides, Synchrotron.
Subject
Chemistry and Materials Science, Materials Science and Technology
Copyright:
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
