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 MoO3 ultrathin nanoflowers are shielded by oxygen, making it difficult for efficient gas adsorption. Here, oxygen atoms on the surface of MoO3 nanoflowers (MoO3 NFs) were knocked out based on a simple hydrogenation strategy to obtain MoO3 defective nanoflowers (MoO3 DNFs) with abundant molecular traps and exposed Mo sites. Notably, the response of MoO3 DNFs-10 to 2 ppm H2S is 3 times that of MoO3 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 H2S molecules to facilitate further adsorption. On the other hand, exposed Mo sites have higher charge activity and exhibit higher adsorption capacity for H2S 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.