Exposed Mo atoms induced by micropores enhanced H₂S sensing of MoO₃ nanoflowers

It is well known that the metal atoms of metal oxide semiconductor (MOS) exhibit significant activity in gas sensing. However, limited by the shielding effect of the outer oxygen atom layer, layered MoO₃ is often difficult to show ideal gas adsorption activity. Hence, the MoO₃ microporous nanoflowers (MPNFs) assembled by porous two-dimensional nanosheets were successfully synthesized and exhibited excellent gas sensing performance to H₂S, and the response was 7.2 times higher than that of simple MoO₃ nanosheets. The abundant pores of MoO₃ MPNFs were due to the influence of the crystal cell shrinkage effect on the atomic arrangement, while the significantly enhanced gas sensing performance was attributed to the positive effect of the microporous structure on gas diffusion and the exposed edge Mo atoms. This was confirmed by DFT calculation results that, compared to the Mo atoms on the surface of MoO₃ nanosheets, the Mo atoms around the pores were exposed because they broke through the shielding effect of the oxygen atom layer and exhibited higher adsorption activity for H₂S and O₂ molecules. Therefore, this work can shed a light on the design of high-performance gas sensors based on metal oxides.