Generation of Double-Layer Steps on (010) Surface of Orthorhombic MoO3 via Chemical Etching at Room Temperature

Using the methods of atomic force microscopy, X-ray diffraction and Fourier transform infrared spectroscopy, chemical etching of the (010) surface of flux-grown orthorhombic MoO3 (α-MoO3) single crystals has been investigated in detail. The (010) surface was etched repeatedly in a 0.08 M NaOH aqueous solution, and its topographies were recorded to reveal the evolution patterns upon the etching time. It is found that the “molecular steps” at a height of a single double-layer of MoO3 (6.9 A, or 1/2 bo) can be generated on the surface of (010) in the basic solution. A “layer-by-layer” etching mechanism proposed previously has been confirmed in this model catalyst fabrication. The observed etch pit volumes and multiple-step formation have also been addressed. Although they are created at room temperature, the surface steps/edges are chemically and thermally stable in a common operating temperature range of 350−400 °C. The fabrication/modification of future catalysts via chemical etching is anticipated, since ...