The cost and availability of platinum, together with degradation phenomena that are directly or indirectly caused by the use of a precious-metal catalyst, are major obstacles to the commercialization of incumbent polymer electrolyte membrane fuel cell (PEMFC) technologies. The Flowcath (R) fuel cell technology is a highly promising alternative to the conventional PEMFC that avoids many of these issues. While the anode resembles that of a conventional cell, the novel cathode employs a liquid-based polyoxometalate redox mediator and is entirely free of any precious metals. A transition-metal based redox centre within the polyoxometalate undergoes reversible reduction in the cathode and is regenerated externally using air. In this paper, the performance of the cell for different catholyte flow rates and polyoxometalate concentrations is described and a first model is developed and validated. The voltage losses are quantified and compared to the values for a conventional cell employing a standard membrane electrode assembly. (C) 2011 Elsevier B.V. All rights reserved.