A Fe3O4(111) surface with both Lewis acid and base sites is formed by reducing α-Fe2O3(0001). The dual Lewis sites are composed of O adatoms and Fetet1 atoms. Combining scanning tunneling microscopy (STM) and density functional theory (DFT), the atomic structure of the Fe3O4(111) surface was identified using the fingerprint of electronic structure of Oad and uncovered Fetet1. Dimethyl methylphosphonate (DMMP) dissociates to yield methoxy and methyl methyl phosphonate, (CH3O)P(O)2(CH3), on the Fe3O4(111) surface at room temperature. At higher temperatures, dimethyl ether forms via intramolecular reaction, followed by formation of formaldehyde and methanol from adsorbed methoxy decomposition during temperature programmed reaction. Ultimately, stochiometric combustion at 870 K to produce CO, H2C=O, CO2 via reaction with lattice oxygen; with POx remaining on the surface. Excess oxygen from the bulk is required to drive these higher temperature pathways. Neither hydrolysis, nor a photoreaction is observed, when exposing the adsorbed DMMP to water or light above the bandgap, respectively. No evolution of P-containing species is detected, indicating efficient trapping of this contaminant. The activity for DMMP decomposition at room temperature is reduced by the accumulation of POx. However, a significant amount of reaction persists after multiple temperature programmed reaction experiments.

Dual Lewis sites on Fe3O4(111) films facilitate DMMP decomposition

ACS Spring Meeting 2021

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