Interface-tuned selective reductive coupling of nitroarenes to aromatic azo and azoxy: a first-principles-based microkinetics study

Abstract

It is of great importance to regulate a catalyst to control its selectivity. In general, the Pt catalyzed hydrogenation of nitrobenzene (PhNO₂) would produce aniline. Yet, when KOH is added, the more value-added N–N coupling products such as aromatic azoxy and azo exhibit better selectivity. To identify the key factors governing the selectivity towards aromatic azoxy and azo in a complex reaction network, the reaction mechanisms of PhNO₂ hydrogenation over Pt(111) are systematically investigated on the Pt(111) surface and at the KOH/Pt(111) interface utilizing microkinetic simulations based on the PBE-D3 calculated results. It is found that the selectivity strongly depends on the adsorption configuration of PhNO₂ rather than on the coverage of the surface H*. In neutral environments, PhNO₂ tends to lie flat on the Pt(111) with chemisorption of the phenyl group, which is in favor of the production of aniline. The addition of KOH makes PhNO₂ preferentially chemisorb at the KOH/Pt(111) interface via the nitro group without the chemisorption of the phenyl group, which is in favor of the N–N coupling products. The KOH-induced tilted adsorption configuration and extra stabilization could promote the dehydroxylation of PhNOH* to form PhN*, which is the key intermediate for the production of azoxy and azo.