It is shown that low temperature (<100 degrees C) hydrogen treatment of nano nickel boride catalysts is an efficient process for the enhancement of their activity in the p-nitrophenol (PNP) to p-aminophenol (PAP) hydrogenation reaction. It has been shown that such a process excludes initial borate species present on the surface and within the catalyst nano-particles by promoting their dissolution in the liquid phase. The latter phenomenon is enhanced by increasing the temperature. Treatment in the absence of hydrogen results in no reaction rate enhancement. Instead, the activity falls significantly below that of the as-synthesized catalyst. The effect of hydrogen treatment on the catalyst physical properties was investigated using FTIR, XRD, nitrogen adsorption and FESEM analysis. Mathematical simulation of the PNP hydrogenation reaction rate supports the hypothesis that the rate enhancement is mainly due to the increase of the catalyst specific surface area and partial reduction of surface nickel oxide species. The mechanism by which hydrogen increases the specific surface is discussed. (C) 2013 Elsevier B.V. All rights reserved.