Molecular traps and exposed Mo sites induced by oxygen knockout enhanced H2S sensing of MoO3 nanoflowers

Limited by the dense arrangement of oxygen atoms in the outer layer, the active Mo sites of MoO 3 ultrathin nanoflowers are shielded by oxygen, making it difficult for efficient gas adsorption. Here, oxygen atoms on the surface of MoO 3 nanoflowers (MoO 3 NFs) were knocked out based on a simple hydrogenation strategy to obtain MoO 3 defective nanoflowers (MoO 3 DNFs) with abundant molecular traps and exposed Mo sites. Notably, the response of MoO 3 DNFs-10 to 2 ppm H 2 S is 3 times that of MoO 3 NFs. Oxygen atom knockout was verified based on Laser Raman Spectroscopy, Photoluminescence (PL), UV–Visible Spectroscopy (UV–Vis), and X-ray photoelectron energy Spectroscopy (XPS), while calculations based on density functional theory (DFT) were used to reveal the sensing enhancement of molecular traps and exposed Mo sites. On the one hand, molecular traps can effectively trap H 2 S molecules to facilitate further adsorption. On the other hand, exposed Mo sites have higher charge activity and exhibit higher adsorption capacity for H 2 S gas. This work breaks through the limitations of the traditional oxygen vacancy model and innovatively discusses the synergistic effect of molecular traps and exposed Mo sites on enhanced sensing, which can provide a reference for the gas sensing by metal oxide semiconductors.