Mesoporous ZnO nanosheets with rich surface oxygen vacancies for UV-activated methane gas sensing at room temperature

Photoactivation is a promising approach for room-temperature gas sensing with metal oxide semiconductors. For room-temperature methane (CH4) gas sensors, it is highly desirable to develop sensing materials with high photocatalytic CH4 oxidation activity so as to improve their UV-activated CH4 sensing performance. Herein, we reported that mesoporous ZnO nanosheets with rich surface oxygen vacancies (V-O) exhibited enhanced CH4 sensing properties under UV illumination at room temperature. The V-O-enriched mesoporous ZnO nanosheets were fabricated via a low-temperature thermal phase transformation route. Under UV irradiation, the V-O-rich ZnO nanosheets demonstrated a response of 62 % to 0.1 % CH4, about 4.7 times higher than that of V-O-deficient commercial ZnO nanoparticles. The improved CH4 sensing capacity of the porous ZnO nanosheets under UV illumination was correlated to their enhanced photocatalytic oxidation activity of CH4 induced by surface V-O. The in-situelectron paramagnetic resonance and O-2 temperature programmed desorption analysis indicated that the generation of Zn+/O- active centers and active oxygen species could be promoted by the rich surface V-O on mesoporous ZnO nanosheets. Furthermore, the density functional theory calculations suggested that V-O could improve the surface charge density of ZnO and lower the Gibbs free energy for the CH4 activation on the ZnO surface.