In Situ TEM Reveals Direct One-Step Reduction of van der Waals Crystal MoO<sub>3</sub> to Mo.
basic_science · Level V
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- Record sourced from PubMed, PMID 40906613.
- Also identified by DOI 10.1021/acs.nanolett.5c03929.
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Abstract
Molybdenum oxides (MOs) exhibit rich polymorphism and tunable properties, yet their phase transformation pathways are poorly understood. Here, we employ in situ environmental transmission electron microscopy (TEM) to reveal a direct reduction of MoO<sub>3</sub> to metallic Mo, bypassing known intermediate phases such as MoO<sub>2</sub> and Mo<sub>4</sub>O<sub>11</sub>. Surface nucleation begins at approximately 800 °C and is completed at 900 °C. Molecular dynamics (MD) and density functional theory (DFT) calculations attribute this unexpected transformation to the van der Waals (vdW) layered structure of MoO<sub>3</sub>, which lowers both the oxygen binding energy and the Gibbs free energy (ΔG) for oxygen desorption under high-vacuum and high-temperature conditions. Preferential oxygen removal from the weakly bonded vdW layers facilitates a rapid reduction to the metallic phase. These findings uncover a nonclassical reduction mechanism and provide a pathway for the rational design of MOs with controllable phases and properties.