High-response H2 sensing performances of ZnO nanosheets modulated by oxygen vacancies

Abstract

Metal oxide semiconductor-based chemiresistors have been facing challenges in achieving low-temperature hydrogen sensing at the ppb level. The oxygen vacancy is considered to play a vital role in gas sensing properties. However, a nonstoichiometric metal oxide semiconductor with efficient and controllable oxygen vacancies is not easily accessible. Herein, a facile solution reduction method of NaBH₄ was developed to modulate the oxygen vacancies of ZnO nanosheets. The systematic characterization studies confirm the successful introduction of oxygen vacancies in ZnO samples. The gas sensing investigations illustrate that the construction of controlled oxygen vacancies greatly enhances the hydrogen sensing properties of ZnO nanosheets, especially a significantly reduced operating temperature (150 °C) with a higher response (∼38.2 for 200 ppm), a calculated limit of detection (55 ppb) and a quick recovery speed (only 6 s). The increased molecule adsorption and narrower band gap generated by controlled oxygen vacancies contribute to their superior sensing properties. The oxygen vacancy engineering strategy of pure metal oxide semiconductor-based materials shows great potential for creating low-temperature high-response sensors.