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Scanning Electrochemical Microscopy (SECM) feedback mode and substrate generation-tip collection (SG-TC) mode coupled with chronoamperometric approach were used to investigate H2 oxidation and hydrogen evolution reaction (HER) at a polyaniline (PAni) coated highly oriented pyrolytic graphite (HOPG) electrode. Using the former mode, the heterogeneous electron transfer (ET) kinetics for H2 oxidation was studied, while the latter mode allowed mapping of the distribution of local [H2] at the nanoparticulate/aqueous interface, followed by monitoring the transients at the tip. These preliminary studies demonstrate that SECM is useful in evaluating the activity of nanophase electrocatalysts. Particularly, if one employs nanometer-sized tips or hydrodynamic microjet electrodes where the mass transfer rate is significantly high, it should be possible to investigate the ET kinetics more accurately.