The effect of carbonate ion species on the direct ammonia fuel cell (DAFC) employing anion exchange membrane (AEM) was evaluated. The OH-form and HCO3-form AEMs were applied as electrolytes for DAFCs. The obtained current density of DAFC with HCO3-form AEM was 1/7 of that with OH-form AEM. This is because carbonate ion species in the AEM suppress the ammonia oxidation reaction on Pt/C anode. Under the presence of carbonate ion species in the electrolyte, the ammonium ion and carbamate ion were formed accompanied with a reduction in the ammonia concentration in the vicinity of anode. This phenomenon affected the open circuit voltage (OCV) of DAFC with HCO3-form AEM. (C) The Author(s) 2016. Published by ECS. This is an open access article distributed under the terms of the Creative Commons Attribution Non-Commercial No Derivatives 4.0 License (CC BY-NC-ND, http://creativecommons.org/licenses/by-nc-nd/4.0/), which permits non-commercial reuse, distribution, and reproduction in any medium, provided the original work is not changed in any way and is properly cited. For permission for commercial reuse, please email: [email protected]. All rights reserved.