The use of bipolar membranes (BMs), modified by plasma-induced polymerization, as diaphragms for H-2 production from water electrolysis, is discussed in this paper. The performance is demonstrated by measuring the cell voltage and rate of hydrogen production for cells operated with or without the BMs, as a function of current densities. The results of the electrochemical properties of the BMs show that the polyvinylidene fluoride-grafted 2-methacrylic acid 3-(bis-carboxymethylamino)-2-hydroxyl-propyl ester (PVDF-grafted-GMA-IDA) BM has great potential for water electrolysis in 0.1 M KCl. As a result of characterization of the steady-state E-I curves, cell voltage reductions of up to 500 and 300 mV by using the PVDF-grafted-GMA-IDA and polyethersulfone-grafted-GMA-IDA (PES-grafted-GMA-IDA) BMs, respectively, are observed at 250 mA/cm(2) in 0.1 M KCl, compared to the water system. The efficiency of H-2 production, by using the BMs grafted onto the GMA-IDA monomer as diaphragms is enhanced about 10-20% compared with the water system. In addition. the energy saved by using the GMA-IDA grafted BMs is decreased by around 10-40% at certain values of current densities. Crown Copyright (C) 2009 Published by Elsevier B.V. All rights reserved.