RuS2 and cobalt-doped RuS2 are good catalysts for electrochemical hydrogen evolution in a hydrogen bromine proton exchange membrane based electrochemical flow cell, but their activity for hydrogen oxidation is low. We used temperature programmed reaction (TPR) methods to study the formation of BD from gaseous H-2 and D-2 catalyzed by these electrode materials. We found that they are active for HD exchange at room temperature and conclude that electrochemical hydrogen oxidation is not limited by the inability of the electrodes to adsorb or dissociate hydrogen. Therefore, we further conclude that the low activity for hydrogen electrooxidation on these semiconducting chalcogenides is due to electronic factors which limit the ability of the semiconductors to accept electrons or pass current. We recommend therefore the use of conducting compounds stable in HBr. (C) 2013 The Electrochemical Society. All rights reserved.