Specifically, it is due to the competitive adsorption of phenyl and N-containing groups in the process of PhNO2 hydrogenation. The weak bond between the adsorbate and the surface is more conducive to association reactions such as hydrogenation. Since hydrogenation usually requires energy to partially destroy the bond between intermediate and surface atoms to form the bond between intermediate and hydrogen, the weaker the bond between intermediate and surface atoms, the lower the hydrogenation barrier.