A numerical analysis of a membraneless microfluidic fuel cell with a Y-shaped microchannel is performed to determine the effects of geometric modifications on the performance. The geometry of the fuel cell is changed in various ways. Variations in the width, height, and length of the channel with and without tapered electrodes are tested in terms of power and current densities. A comparative analysis is performed for ten cross-sectional shapes of the channel, which are designed to change the depletion region, the mixing region, and the electrodes' surface areas. Three configurations of the channel and electrodes are also tested. Formic acid and oxygen are used as the fuel and oxidant, respectively, which are dissolved in a sulfuric acid solution. Simulations are performed using three-dimensional Navier-Stokes equations for flow, and the mass transport equation for species concentration. The electrochemical reaction kinetics are modeled using the Butler-Volmer equations for a microfluidic vanadium fuel cell. Based on the results, a tapered channel with tapered electrodes is recommended for the performance enhancement of a microfluidic fuel cell. (C) 2017 Elsevier Ltd. All rights reserved.