Reduced SnO2-x for Low Power NO2 Gas Sensors: From First Principles Simulations to Sensing Performance

Semiconducting metal oxides are the most studied materials for gas sensing application due to their outstanding high sensitivity, good stability and low production costs. However, despite these advantages, the devices suffer weakness in their performance, including the lack of selectivity and high working temperature, which results in high-power consumption. In this work, a simple and low-cost method was used to synthesize reduced SnO2-x to produce gas sensors that can be operated at low operation temperatures. The combined use of theoretical Density Functional Theory and in-depth characterization of SnO2-x samples allowed to investigate both superficial and bulk oxygen vacancies created. The results achieved confirm that the simple and low-cost method, used in this work, successfully reduces SnO2 samples, and based on the theoretical investigation the reduction of this kind of materials may lower the sensor operating temperature. Indeed, the electrical characterizations of the sensor showed the highest sensitivity at 70 °C instead of the common operating temperature of SMOX-based gas sensors (ranging from 300 to 600 °C).