Blending noble metal catalysts with inexpensive transition metals can reduce material cost in catalytic water treatment by improving the catalytic reactivity. An important challenge is, however, to synthesize a series of alloy nanoparticles with varied compositions so that the screening of catalytic reactivity can be performed rapidly for a contaminant of interest. Here, we report a facile approach for the rapid synthesis of bimetallic nanoalloys using cycle-controlled microwave-assisted polyol reduction, with an option of fixing the nanoalloys directly on graphene supports in a one-pot operation. Using Pt and Ni as the model noble and promoter metals, we show that Pt/Ni nanoparticles with diameters ranging from 2.8 to 4 nm can be readily synthesized within minutes. The surface Ni percentage of the nanoparticles are varied from 0 to 100%, which serves as a model system for nanoalloy screening. Using the model contaminant p-nitrophenol, we further show that the reactivity-composition relationship has a classic volcano shape as the Sabatier principle predicts. The highest reactivity is found with a surface Ni percentage of approximately 50%. (C) 2014 Elsevier B.V. All rights reserved.