Electrochemical detection of H-2 using scanning electrochemical microscopy (SECM) has shown to hold great promise as a sensitive characterization method with high spatial resolution for active surfaces generating H-2. Herein, the factors contributing to the current that is measured by SECM in generation/collection mode for H-2 detection are studied. In particular, the concentration gradient of H-2 at the substrate, the H-2/H+ recycling between the SECM tip and substrate and hemispherical profile of H-2 diffusion has been discussed. It was postulated that H-2/H+ recycling plays a dominant role in the oxidative current measured in generation/collection mode of SECM when the microelectrode is positioned in close vicinity of substrate. Copyright (C) 2015 John Wiley & Sons, Ltd.