The purpose of this study was to produce hydrogen gas by electrolysis of coal slurries and to investigate the relation between hydrogen (H-2) and carbon dioxide (CO2) formation. Electrolysis of coal slurries was evaluated at 40 degrees C and 1.0 V cell potential to examine H-2 and CO(2)relationship. When electrolysis was performed after the coal slurry was mixed with Fe(II)/Fe(III) ions and stirred overnight (>12 h), no CO2 gas was observed at the anode compartment. The results of total organic carbon (TOC) indicated that after electrolysis, few organic compounds were transformed into the solution and these organic compounds did not convert into CO2. GC analysis, on the other hand, revealed that the H-2 collected at the cathode was pure and did not require any further purification process. Hydrogen generation or electrolysis efficiency of coal slurries cannot be calculated or estimated by examining CO2 generation as reported in the literature. Low temperature and low cell potential were not sufficient to oxidize coal quantitatively. Copyright (C) 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.