g-C3N4 templated synthesis of 3DOM SnO2/CN enriched with oxygen vacancies for superior NO2 gas sensing

Materials with three-dimensional ordered macroporous (3DOM) structures possess large surface area and abundant macropores, providing more surface active adsorption sites and target gas transport channels. Herein, g-C3N4 was utilized as a hard template to fabricate 3DOM SnO2/CN composites. After calcinating the g-C3N4-metal ions hybrids in air, most of the carbon and nitride sources were removed, leaving metal oxides with the original 3DOM structures. The residual carbon and nitride also generated amorphous CN species, significantly boosting the conductivity of the mixed composites. Moreover, large amounts of oxygen vacancy defects were also created after the pyrolysis treatment. Sensing results displayed that all SnO2/CN composites under different heating rates displayed excellent sensing response to NO2 gas. Excitingly, sensors with 10 °C min−1 heating rate exhibited a superior response of 926 to 10 ppm NO2 gas at room temperatures (RT, 25 °C) and a low detection limit of 15 ppb. Such high NO2 sensing performance was caused by the open 3DOM structures and abundant oxygen vacancies. Most importantly, this work provides a novel approach to fabricate sensing materials with 3DOM structures and will also promote the practical application of NO2 sensors.