Supported Ni0@C N catalyst with dual-reaction surfaces: Structure-performance relation in the selective hydrogenation of p-chloronitrobenzene

How to break the activity-selectivity dependence in halonitrobenzene hydrogenation remains a challenge. In this work, [email protected]N/SiO2 were synthesized and examined in the hydrogenation of p-chloronitrobenzene. It showed that the electron transferred from nitrogen doped carbon shell to Ni0 core (core–shell synergistic effect) dominated the intrinsic activities of [email protected]N/SiO2 with dual-reaction surfaces (H2 dissociated on Ni0 core, while p-chloronitrobenzene was hydrogenated on carbon shell) in the thiophene-free hydrogenation, leading to their higher turnover frequencies than Raney Ni catalyst. During the thiophene-involved hydrogenation, the adsorption of thiophene on Ni0 changed its electron density and blocked the active sites. These enhanced the selectivity, but significantly reduced the activity for Raney Ni catalyst. Comparatively, the carbon shell protected Ni0 core from thiophene adsorption so that the hydrogen dissociated on Ni0 as usual. However, the adsorption of thiophene on the carbon shell reduced the available sites for p-chloronitrobenzene adsorption. Although [email protected]N/SiO2 had lower activities in the thiophene-involved reactions than those of thiophene-free reactions, they achieved ∼100 % p-chloroaniline selectivities and 8-fold higher turnover frequencies than Raney Ni, breaking the activity-selectivity dependence. This reveals that the available sites on the carbon shell and the core–shell synergistic effect determine the thiophene-involved hydrogenation activities of [email protected]N/SiO2 catalysts.