Engineered Porosity ZnO Sensor Enriched with Oxygen Vacancies Enabled Extraordinary Sub-ppm Sensing of Hydrogen Sulfide and Nitrogen Dioxide Air Pollution Gases at Low Temperature in Air.

We report the results of a zinc oxide (ZnO) low-power microsensor for sub-ppm detection of NO and HS in air at 200 °C. NO emission is predominantly produced by the combustion processes of fossil fuels, while coal-fired power plants are the main emitter of HS. Fossil fuels (oil, natural gas, and coal) combined contained 74% of USA energy production in 2023. It is foreseeable that the energy industry will utilize fossil-based fuels more in the ensuing decades despite the severe climate crises. Precise NO and HS sensors will contribute to reducing the detrimental effect of the hazardous emission gases, in addition to the optimization of the combustion processes for higher output. The fossil fuel industry and solid-oxide fuel cells (SOFCs) are exceptional examples of energy conversion-production technologies that will profit from advances in HS and NO sensors. Porosity and surface activity of metal oxide semiconductor (MOS)-based sensors are both vital for sensing at low temperatures. Oxygen vacancies (VO••) act as surface active sites for target gases, while porosity enables target gases to come in contact with a larger MOS area for sensing. We were able to create an open porosity network throughout the ZnO microstructure and simultaneously achieve an abundance of oxygen vacancies by using a heat treatment procedure. Surface chemistry and oxygen vacancy content in ZnO were examined using XPS and AES. SEM was used to understand the morphology of the unique characteristics of distinctive grain growth during heat treatment. Electrical resistivity measurements were completed. The valance band was examined by UPS. The Engineered Porosity approach allowed the entire ZnO to act as an open surface together with the creation of abundant oxygen vacancies (VO••). NO detection is challenging since both oxygen (O) and NO are oxidizing gases, and they coexist in combustion environments. microsensor detected sub-ppm NO under O interference, which affects mimicking realistic sensor operation conditions. performed better than the previous literature findings for HS and NO detection. The exceptionally high sensor response is attributed to the VO•• and . These features enhance gas adsorption and diffusion via porosity, leading to high sensor response.