Microfluidic fuel cells have low power density and poor fuel utilization due to the generation of a reaction depletion zone. In this study, cell electrodes patterned with grooves are proposed for passive control of the depletion zone, where a secondary transport flow over the grooved electrode replenishes the depleted layers. The proposed membrane-less fuel cell is composed of a polydimethylsiloxane layer over a photoresist microchannel wall and a glass substrate that contains platinum electrodes. The optimum gap between the electrodes and the height of grooves are designed based on a computational fluid dynamics simulation. Hydrogen peroxide is used both as a fuel (when it is mixed with sodium hydroxide) and as an oxidant (when it is mixed with sulfuric acid). During the experiments, electrodes of various lengths are integrated on the bottom of the Y-channel. Experimental results show that the effect of grooves on cell performance is independent of fuel rate and fuel concentration, but the effect is remarkable when the length of the electrode is large. The peak power density with grooved electrodes improves by a maximum of 13.93% compared to that of planar electrodes. This grooved electrode-based fuel cell is expected to be a useful microdevice for power generation. (C) 2014 Elsevier B.V. All rights reserved.