One of the most important issues in the research related to Zn-air batteries is the hydrolysis of the aqueous solution. We have investigated the effectiveness of Zn ions and the anions of various acids as gas suppressants in the battery. Zn ions can function as a gas suppressant on a Pt surface, but they can stimulate additional gas production when they are deposited as Zn metal. On the other hand, the counter anions of weak acids behave as adsorbates to cover Zn metal effectively. (C) 2009 Elsevier Ltd. All rights reserved.