Appropriate aggregation is needed for highly active Pt/Al 2 O 3 to enable hydrogenation of chlorinated nitrobenzene.

The atomic dispersion of a noble metal with a reducible support has been reported to be beneficial for catalytic hydrogenation reactions. Conversely, we found that Pt particles (3-5 nm) could be obtained on the non-reducible support Al 2 O 3 by weakening the interaction between the metal and support using oleic acid, and the turnover frequency of catalyzing the hydrogenation of chlorinated nitrobenzene could reach 3700 h -1 , which is three orders of magnitude higher than that of atomic platinum species.