Engineering of Thickness Tunable 2D Graphdiyne Film to ZnO Nanowalls via Nanospace-Confined Synthesis Promotes NO2 Gas Sensing Performance

Achieving rapid response and recovery rates at low operating temperatures for NO2 is desirable for the application of sensors in industrial safety. In this study, we integrate a thickness tunable 2D graphdiyne (GDY) film into ZnO nanowalls (GDY/ZnO) via thermal evaporation of GDY, where ZnO nanowalls are used as the template to confine the growth space of the GDY film. In situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) is used to reveal the transformation process of NO2. Ultraviolet photoemission spectroscopy (UPS) is utilized to analyze changes about the energy band of the materials. Density functional theory (DFT) calculations explain the reason for the selectivity of the samples to NO2. The scanning electron microscopy (SEM) results demonstrate that the thickness of the GDY film with a specific mesoporous structure (25-53 nm) increases as the thermal evaporation temperature rises from 400 to 800 degrees C.The representative ZG-600, synthesized with a thickness of 46 nm via thermal evaporation at 600 degrees C, exhibits superior NO2 sensing performance. This is evidenced by its ultrahigh response (13.86, at 100 ppm and 150 degrees C) and rapid response/recovery speeds (150 s/ 198 s), outperforming the ZnO sensor (198 s and 326 s). Moreover, it offers remarkable stability.