Direct vs. indirect pathway for nitrobenzene reduction reaction on a Ni catalyst surface: a density functional study

Area of Science:

• Catalysis
• Computational Chemistry
• Surface Science

Background:

• Experimental studies suggest direct reaction pathways are preferred for nitrobenzene to aniline reduction, regardless of the catalyst.
• Nitrobenzene to aniline conversion can proceed via direct (hydroxyl amine intermediate) or indirect (azoxybenzene intermediate) pathways.

Purpose of the Study:

• To computationally investigate the reaction mechanisms for nitrobenzene reduction to aniline over a Nickel (Ni) catalyst.
• To elucidate the preferred adsorption orientation of nitrobenzene on the Ni catalyst surface.
• To compare the energetic favorability of direct versus indirect reaction pathways.

Main Methods:

• Density Functional Theory (DFT) calculations were employed.
• Spin-polarized and dispersion-corrected reaction energies and activation barriers were computed.
• Adsorption behavior of nitrobenzene on the Ni catalyst surface was analyzed.

Main Results:

• Parallel adsorption of molecules on the catalyst surface was found to be more energetically favorable than vertical adsorption.
• The direct reduction pathway of nitrobenzene to aniline over the Ni(111) catalyst surface exhibits lower reaction energies and activation barriers.
• The direct pathway is computationally determined to be more favorable than the indirect pathway.

Conclusions:

• The computational findings support experimental observations favoring direct reaction pathways for nitrobenzene to aniline reduction.
• The Ni(111) catalyst surface promotes the direct reduction pathway due to lower activation energy barriers.
• Understanding these mechanistic details is crucial for designing efficient catalysts for aniline production.