A series of Dawson-type heteropolyanions (HPAs) mono-substituted with transitional metal ions ((alpha 2)- [P2W17O61FeIII](8-), (alpha 2)-[P2W17O61CuII](8-) and (alpha 2)-[P2W17O61NiII](8-)) have exhibited electrocatalytic properties towards nitrate and nitrite reduction in slightly acidic media (pH 4.5). The immobilization of these HPAs into water-processable films developed via layer-by layer assembly with polymer-stabilized silver nanoparticles led to the fabrication of the electrocatalytic interfaces for both nitrate and nitrite reduction. The LBL assembly as well as the changes in the HPA properties by immobilization has been characterized by electrochemical methods. The effects of the substituent ions, outer layers and the cationic moieties utilized for the films assembly of the developed film on the performances of nitrate electrocatalysis has been elucidated. (C) 2015 Elsevier Ltd. All rights reserved.