A demonstration of direct formic acid fuel cells (DFAFCs) generating relatively high power density at ambient temperature is reported. The performance of Nafion 112-based DFAFCs with different concentrations of formic acid at different temperatures has been evaluated. DFAFCs operated with dry air and zero back-pressure can generate power densities of 110 and 84 mW cm(-2) at 30 and 18 degreesC, respectively, which are considerably higher than direct methanol fuel cells (DMFCs) operated under the same conditions. The DFAFCs are especially suited to power portable devices used at ambient temperature because the significant high power density can be achieved with highly concentrated formic acid. (C) 2004 Elsevier B.V. All rights reserved.