Porous MoO3-x nanobelt: synthesis, characterization and catalytic application

Porous MoO3-x nanobelts were synthesized by hydrothermal method at 373 K with using P123 as surfactant. The synthesized nanobelts are pure orthorhombic α-MoO3 structure, with the length up to more than 10 mm and width ranging from 20 to 100 nm. The chemical formula is determined to be MoO2.44•0.48H2O and the average valence of Mo is +5.1 by TG and XPS measurements. N2 adsorption-desorption isotherms confirmed the presence of microspore and mesorpores, which is further evidenced by TEM observation. Raman spectra also confirmed the synthesized MoO3-x present the α-MoO3 structure, and these nanobelts might grow along the c axis due to the very higher vibrational intensity of Mo-O-Mo at 820 cm-1. Detailed works on tuning the conditions of hydrothermal synthesis were performed to study the MoO3-x formation mechanism. α -MoO3 via acidification of Na2MoO4•H2O formed at first, and it will be reduced to MoO3-x by P123 under hydrothermal conditions. With the hydrothermal temperature further increased up to 433 K, MoO2 with monolithic structure appeared. More importantly, the MoO3-x nanobelts showed quite promising activity for ethanol oxidation to acetaldehyde, with 78% conversion of ethanol and 79% selectivity of acetaldehyde at 593 K.