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Study on Synergistic Mechanism of Inhibitor Mixture Based on Electron Transfer Behavior

View Article: PubMed Central - PubMed

ABSTRACT

Mixing is an important method to improve the performance of surfactants due to their synergistic effect. The changes in bonding interaction and adsorption structure of IM and OP molecules before and after co-adsorbed on Fe(001) surface is calculated by DFTB+ method. It is found that mixture enable the inhibitor molecules with higher EHOMO donate more electrons while the inhibitor molecules with lower ELUMO accept more electrons, which strengthens the bonding interaction of both inhibitor agent and inhibitor additive with metal surface. Meanwhile, water molecules in the compact layer of double electric layer are repulsed and the charge transfer resistance during the corrosion process increases. Accordingly, the correlation between the frontier orbital (EHOMO and ELUMO of inhibitor molecules and the Fermi level of metal) and inhibition efficiency is determined. Finally, we propose a frontier orbital matching principle for the synergistic effect of inhibitors, which is verified by electrochemical experiments. This frontier orbital matching principle provides an effective quantum chemistry calculation method for the optimal selection of inhibitor mixture.

No MeSH data available.


Frontier orbital energetic positions of OP molecule (a), IM molecule (b) and IM + OP molecules (c) adsorption on Fe(001) surface.
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f6: Frontier orbital energetic positions of OP molecule (a), IM molecule (b) and IM + OP molecules (c) adsorption on Fe(001) surface.

Mentions: The bonding interaction between adsorbed molecules and metal surface depends on the frontier orbital energetic position of adsorbed molecules and the Fermi level of metal36. Figure 6 shows the frontier orbital energies of IM and OP molecules before and after mixture. For OP molecule, the EHOMO (−5.887 eV) of OP molecule is close to the Fermi level of Fe(−5.177 eV) while the ELUMO (−0.305 eV) of OP molecule is far away from the Fermi level of Fe. Thus, electrons likely excited from the HOMO orbital of OP molecule to Fe surface. Moreover, the amount of the transferred electrons is large. However, the energy gap between ELUMO of OP molecule and the Fermi level of Fe is large. Therefore, it is difficult for the electrons to be excited from Fe surface to the LUMO orbital of OP molecule. Generally speaking, OP molecule donates electrons and thus electrons accumulate on Fe surface until the electron transfer reaches equilibrium. During this process, the frontier orbital energetic positions of OP molecule shift to the lower level, while the Fermi level of Fe is considered to be no significant change37.


Study on Synergistic Mechanism of Inhibitor Mixture Based on Electron Transfer Behavior
Frontier orbital energetic positions of OP molecule (a), IM molecule (b) and IM + OP molecules (c) adsorption on Fe(001) surface.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5037402&req=5

f6: Frontier orbital energetic positions of OP molecule (a), IM molecule (b) and IM + OP molecules (c) adsorption on Fe(001) surface.
Mentions: The bonding interaction between adsorbed molecules and metal surface depends on the frontier orbital energetic position of adsorbed molecules and the Fermi level of metal36. Figure 6 shows the frontier orbital energies of IM and OP molecules before and after mixture. For OP molecule, the EHOMO (−5.887 eV) of OP molecule is close to the Fermi level of Fe(−5.177 eV) while the ELUMO (−0.305 eV) of OP molecule is far away from the Fermi level of Fe. Thus, electrons likely excited from the HOMO orbital of OP molecule to Fe surface. Moreover, the amount of the transferred electrons is large. However, the energy gap between ELUMO of OP molecule and the Fermi level of Fe is large. Therefore, it is difficult for the electrons to be excited from Fe surface to the LUMO orbital of OP molecule. Generally speaking, OP molecule donates electrons and thus electrons accumulate on Fe surface until the electron transfer reaches equilibrium. During this process, the frontier orbital energetic positions of OP molecule shift to the lower level, while the Fermi level of Fe is considered to be no significant change37.

View Article: PubMed Central - PubMed

ABSTRACT

Mixing is an important method to improve the performance of surfactants due to their synergistic effect. The changes in bonding interaction and adsorption structure of IM and OP molecules before and after co-adsorbed on Fe(001) surface is calculated by DFTB+ method. It is found that mixture enable the inhibitor molecules with higher EHOMO donate more electrons while the inhibitor molecules with lower ELUMO accept more electrons, which strengthens the bonding interaction of both inhibitor agent and inhibitor additive with metal surface. Meanwhile, water molecules in the compact layer of double electric layer are repulsed and the charge transfer resistance during the corrosion process increases. Accordingly, the correlation between the frontier orbital (EHOMO and ELUMO of inhibitor molecules and the Fermi level of metal) and inhibition efficiency is determined. Finally, we propose a frontier orbital matching principle for the synergistic effect of inhibitors, which is verified by electrochemical experiments. This frontier orbital matching principle provides an effective quantum chemistry calculation method for the optimal selection of inhibitor mixture.

No MeSH data available.