Nitrogen-doped carbon nanotubes (N-CNTs) derived from ethylenediamine precursor have been used as air cathode catalyst for zinc-air batteries (ZABs) in half cell and single cell. Investigation of N-CNTs employed a rotating disc electrode system revealed excellent catalytic activity towards oxygen reduction reaction (ORR) in alkaline electrolyte. The influence of alkaline electrolyte concentration on single cell performance of ZABs has also been explored. The highest cell performance was achieved at an electrolyte concentration of 6 M KOH, which resulted in a maximum cell power density of 69.5 mW cm(-2). (C) 2011 Elsevier Ltd. All rights reserved.