The authors propose a new method to easily and reliably determine the exchange current density (i(0)) of hydrogen evolution reaction (her). The validity of a novel method named the differential polarization method (DPM) was ascertained by the estimation of i(0) on platinum electrode in acid solutions. The hers in 0.005, 0.05 and 0.5 mol dm (3) H2SO4 solutions were visually categorized as reversible reactions. The obtained i(0) had constant values of about 0.5 mA cm (2), corresponding to the appearance of a vertical line on the anodic polarization resistance curve. This DPM shows the i(0) is corresponds to the limiting diffusion current density of the hydrogen oxidation reaction. We believe that the DPM has the potential to be a beneficial and reliable method for estimating electrochemical parameters. (C) 2016 Elsevier Ltd. All rights reserved.