Small fuel cells are considered likely replacements for batteries in portable power applications. In this paper, the performance of a passive air breathing direct formic acid fuel cell (DFAFC) at room temperature is reported. The passive fuel cell, with a palladium anode catalyst, produces an excellent cell performance at 30 degrees C. It produced a high open cell potential of 0.9 V with ambient air. It produced current densities of 139 and 336 mA cm(-2) at 0.72 and 0.53 V, respectively. Its maximum power density was 177 mW cm(-2) at 0.53 V. Our passive air breathing fuel cell runs successfully with formic acid concentration up to 10 and 12 M with little degradation in performance. In this paper, its constant voltage test at 0.72 V is also demonstrated using 10 M formic acid. Additionally, a reference electrode was used to determine distinct anode and cathode electrode performances for our passive air breathing DFAFC. (c) 2005 Elsevier B.V. All rights reserved.