A dual electrolyte H-2/O-2 fuel cell system employing a planar microfluidic membraneless fuel cell has been investigated and compared to single electrolyte H-2/O-2 systems under analogous conditions. The fuel is H-2 dissolved in 0.1 M KOH (pH 13), and the oxidant is 02 dissolved in 0.1 M H2SO4(pH 0.9), comprising a system with a calculated thermodynamic potential of 1.943 V (when I M H2 and 02 concentrations are assumed). This value is well above the calculated thermodynamic maximum of 1.229 V for an acid, or alkaline, single electrolyte H-2/O-2 fuel cell. Experimentally, open-circuit potentials in excess of 1.4 V have been achieved with the dual electrolyte system. This is a 500 mV increase in the open circuit potentials observed for single electrolyte H-2/O-2 systems also studied. The dual electrolyte fuel cell system shows power generation of 0.6 mW/cm(2) from a single device, which is nearly 0.25 mW/cm(2) greater than the values obtained for single electrolyte H-2/O-2 fuel cell systems studied. Microchannels of varying dimensions have been employed to study both the single and dual electrolyte H-2/O-2 systems. Channel thickness variation and the flow rate dependences of power generation are also addressed.