The High Potential of the Pure and Nb-Doped δ-FeOOH (001) Surface in the Adsorption and Degradation of a Neurotoxic Agent

The adsorption and degradation of the Soman molecule (Pinacolyl methylphosphonofluoridate, C7H16FO2P) was investigated using the pure and Nb-doped δ-FeOOH (001) surfaces with density functional theory (DFT) calculations. We verified the Soman molecule adsorb on pure and doped surface through interaction preferably via interaction between phosphoryl oxygen (P=O) and hydroxyl groups from surface. The degradation of the Soman molecule on the δ-FeOOH and Nb-δ-FeOOH (001) surfaces was evaluated by the study of the reaction path, were found one transition state for both surfaces, corresponding to a maximum stretch of F-P=O group from Soman molecule and the bond breaking of hydroxyl group bonded to Fe/Nb. The activation energies found are 16.58 and 8.80 kcal/mol to pure and doped surface, respectively. The obtained products consisted of a negatively charged pinacolyl methylphosphonate molecule and HF molecule adsorbed on the positively charged surface. Both δ-FeOOH and Nb-δ-FeOOH (001) surfaces show great potential to adsorb and degrade the Soman neurotoxic agent, however the presence of Nb further favors the process.