We present a simple method to increase the efficiency of a direct ethanol fuel cell by a periodic
modulation of the load (pulsed mode). The fuel cell was periodically short circuited with a resistor
(1 Ω) for a few seconds (high load period) followed by a low load period of up to 100 s when the
resistor was disconnected. The open circuit voltage (OCV) values before and after the short circuit
of the cell showed an increase of up to 70 mV. The higher OCV was due to the oxidation and removal
of strongly adsorbed CO during the electric short circuit when the electric potential of the anode
was increased to be close to the cathode potential. The depoisoned anode surface was much more
active directly after the short circuit. The slow decrease of the OCV observed after the short circuit
was caused by the subsequent poisoning of the anode surface, which can be neutralized by another
short circuit. In general, a stable increase in cell performance was obtained by repetition of the
electric short circuit. The data showed that the pulse mode gave an increase in the power generated
by the direct ethanol fuel cell by up to 51% and was 6% on average. It is anticipated that this mode
of operation can be used also in different types of polymer electrolyte membrane fuel cells where
CO poisoning is a problem, and after optimization of the parameters, a much higher gain in efficiency
can be obtained.