Holey engineered 2D ZnO-nanosheets architecture for supersensitive ppm level H2 gas detection at room temperature

Abstract Conquering the issue of room temperature H2 detection at ppm/ppb level and their fundamental sensing mechanism are vitally needed for the development of highly sensitive/selective sensing devices. Herein, a strategy is proposed to synthesize 2D ZnO holey nanosheets by engineering the tunable pore/hole size with controlled oxygen vacancies using the annealing process for H2 detection at room temperature. 2D ZnO holey nanosheets annealed at 400 °C shows a highly porous network owing to its high surface area, more channels for gas diffusion, and mass transport that exhibits improved gas-sensing performance. ZnO@400 sensor exhibits maximum response of ∼115 (20 times more than ZnO@800 sample) towards 100 ppm of H2 at room temperature. The sensor response (recovery) times of the order ∼9(6) secs recorded to be fastest for ZnO@400 sensor as compared to ZnO@600 (∼19(13) secs) and ZnO@800 (∼27(20) secs) sensor respectively. Further, the ZnO@400 sensor also displays superior repeatability and stability of ∼97−99% after 45 days. The involved gas sensing mechanism has also been verified by carrying out XPS measurements before and after H2 exposure at room temperature that helps to complement the theoretical justification about room temperature metallization effect. Thus, 2D ZnO holey nanosheets turn out to be a pivotal strategy to improve the gas sensing performance due to the synergetic effect of highly porous network and large specific surface areas of 2D nanosheets. The present approach proves to be one of the best methodologies to alleviate the restacking issue of the 2D nanosheets by opening up the inaccessible surfaces.