The electrosynthesis of L-cysteine (RSH) in aqueous medium has been investigated using Pb particles dispersed on carbon as a cathode for L-cystine electroreduction. Pb particles were synthesized in a water-in-oil microemulsion and later dispersed on carbon Vulcan XC-72. The electrochemical characterization of the Pb/C catalyst was carried out by cyclic voltammetry and scanning electrochemical microscopy (SECM). In particular, an approach of the substrate generation/tip collection mode of the SECM has been used for imaging the RSH generation. Different 20 wt % Pb/C-supported cathodes have been fabricated and morphologically characterized. These cathodes were tested for RSH electrosynthesis and compared with a conventional bulk Pb cathode. After a 100% theoretical charge, our three-dimensional 20 wt % Pb/C cathode exhibits a 30% higher RSH yield and current efficiency than the other cathodes. This performance improvement is related to the increase in the available geometric area of this electrode. We demonstrate the feasibility of using Pb/C particles as a catalyst in a type of cathode for RSH electrosynthesis. Moreover, our Pb/C electrodes show a broad scope because they can be applied to other electrosyntheses of valuable organic compounds where bulk Pb is the conventional cathode at present. (C) 2009 The Electrochemical Society. [DOI: 10.1149/1.3208056] All rights reserved.